Conservation Agriculture

Download PDF
Introduction to
Introduction to
Conservation Agriculture
Produced by GrainSA Conservation Farmer Innovation
Programme, with nancial support provided by The Maize Trust
By Mahlathini Organics
To the following people and organisations for assistance in researching,
writing, graphics and general support:
• Erna Kruger: Mahlathini Organics, PO Box 8o7, Richmond
Cell: 082 873 2289; Email:
• Dr Hendrik Smith, GrainSA Conservation Agriculture Coordinator
Cell: 082 331 0456; E mail:
• Contributors: Bergville and Mataitele Smallholder Farmer Innovation
Groups, Field sta including NT Madondo, N Buthelezi, M Dlamini
and S Moloi
• Design and layout: John Bertram, Tangerine Graphic Design
Cell: 082 404 4228; Email:
• Illustrations: Kathy Arbuckle
© GrainSA September 2015
GHG – greenhouse gas
Aggregate – a collection or composite of similar particles
Inltrate – to move into or through something
Nutrient – components or parts of food that organisms use to survive and grow
Organism – a life form such as an animal, plant or micro-organism such as a bacterium or fungus
Healthy soils
Healthy soil is alive
Soils supply essential nutrients, water, oxygen (air) and root support to plants.
Healthy soil is living soil. It contains many living organisms. It is deep, loose,
and easy to dig and full of air and water. Healthy soil has aggregates or struc-
tures (that look like bread crumbs) that create air pockets allowing water to
inltrate or move deep into the soil. Healthy soils act as giant moisture hold-
ing sponges, which is very important in times of drought and ooding.
Healthy soils are naturally fertile and able to supply sucient amounts of nutri-
ents to plants. To do this the soil needs a continuous supply and build-up of organic
matter. Soil health and it’s fertility have a direct inuence on the nutrient content of food crops.
We are
what we eat.
Healthy soils lead to
healthy plants and
healthy people.
Figure 1: Healthy
soil diagram (Based
on Centre for Food safety
2015. Soil and Carbon;
Soil solutions to climate
Food Climate
of nutrients
Increased water
retention and
and oods
More soil
Healthy Soil
This diagram of the carbon cycle shows the movement of carbon
between land, air and oceans in billions of tons of carbon per year.
Yellow numbers are natural ows, red are human contributions
and white numbers indicate stored carbon, usually in liquid or
sold form.
An excess of carbon dioxide (CO2) in the earth’s atmosphere is
warming the planet and increasing the size, number and intensity
of extreme weather events. Some of this excess CO2 is dissolving
into the world’s oceans causing them to become acidic.
Carbon and Soil Organic Matter – the main building
block of life and soil
A key element of all living things, carbon, is constantly cycling through nature as either a liq-
uid a solid or a gas. Soil carbon is sometimes also called organic matter. Because carbon is the
main building block of all organic molecules, the amount in a soil is strongly related to the total
amount of all the organic matter – the living organisms plus fresh residues plus well decom-
posed residues.
Figure 2: The Carbon cycle (From:
More than
90% of the world's
carbon is found in the
deep ocean. On land,
around 805 of carbon
is in the soil.
Why soil organic matter is so
Organic matter has an overwhelming eect on almost
all soil properties, although it is generally present in
relatively small amounts. A typical agricultural soil has
1% to 6% organic matter. It consists of three distinctly
dierent parts – living organisms, fresh residues, and
well decomposed residues. These three parts of soil
organic matter have been described as the living, the
dead, and the very dead.
Functions ascribed to SOM and interactions
Source of energy
Reservoir of nutrients
Soil/plant system resilience
Cation exchange
Soil pH
Binding of SOM to
soil minerals
Structure stability
Water retention
Thermal property
Figure 3: Functions of SOM
The living part of soil organic matter includes a wide variety of microorganisms, such as bac-
teria, viruses, fungi, protozoa, and algae. It also includes plant roots, insects, earthworms, and
larger animals, such as moles and rabbits, that spend some of their time in the soil. The living
portion represents about 15% of the total soil organic matter.
These dierent types of organisms:
ÄHelp to control insect pests, weeds and plant diseases
ÄForm benecial symbiotic relationships with plant roots
ÄRecycle plant nutrients from soil organic matter and minerals back to roots and
ÄImprove soil structure.
SOM composition:
Carbon = 42%,
Oxygen = 42%,
Hydrogen = 8%,
Ash = 8%,
Macronutrients (N, P, K, S, Ca, Mg),
Micronutrients (Fe, Mn, B, Zn, Cu,
Cl, Co, Mo, Ni)
Resilience – the ability to cover from setbacks and stress
Water retention - water holding
Temperature regulation – controlling and adjusting of temperature; keeping temperature changes more even.
Thermal property - temperature regulation
Micro organisms – tiny bugs or creatures that are too small to see with the naked eye
Recycle - re-use - a process of changing wastes into new products
Symbiotic relationships – a cooperative mutually benecial relationship
Microorganisms, earthworms, and insects feed on plant residues and manures for
energy and nutrition, and in the process they mix organic matter into the min-
eral soil. In addition, they recycle plant nutrients. Sticky substances on the skin
of earthworms and other substances produced by fungi help bind particles
together. This helps to stabilize the soil aggregates, clumps of particles that
make up good soil structure.
Organisms such as earthworms
and some fungi also help to
stabilize the soil’s structure (for
example, by producing channels that
allow water to inltrate) and, thereby, im-
prove soil water status and aeration. Plant roots
also interact in signicant ways with the various
microorganisms and animals living in the soil.
The fresh residues, or “dead” organic matter,
consist of recently deceased microorganisms,
insects, earthworms, old plant roots, crop res-
idues, and recently added manures. This part
of soil organic matter is the active, or easily
decomposed fraction and is the main supply
of food for soil organisms As these organic
materials are decomposed by the “living,” they
release many of the nutrients needed by plants
and they also create humus. Organic chemical
compounds produced during the decomposition
of fresh residues also help to bind soil particles
together and give the soil good structure.
Figure 5: A healthy soil has lots of organic matter,
earthworms and other tiny animals in it.
Figure 4: Micro-organisms and small living creatures in the soil (From: Life in the Soil –
In a teaspoon
of healthy soil there
are more microbes
than there are people
on earth.
The well-decomposed organic material in soil, the “very dead”, is called
humus. Micro-orangisms turn the simple sugars or liquid carbon
exuded from plant roots into humus. These simple carbon com-
pounds are joined together into more complex and stable mole-
cules. The formation of stable humus requires a large number
of dierent kinds of soil microbes, including mycorrhizal fungi,
nitrogen xing bacteria and phosphorus solubilising bacteria, all
of which obtain their energy from plant sugars (liquid carbon).
The types of fungi that survive in conventionally managed agricul-
tural soils are mostly decomposers; they obtain energy from decaying
organic matter such as crop residues. Generally, these kinds of fungi have
relatively small hyphal networks. They are important for soil fertility and soil structure, but play
only a minor role in carbon storage.
Mycorrhizal fungi dier from decomposer fungi
in that they get their energy in a liquid form,
as soluble carbon directly from actively grow-
ing plants. There are many dierent types of
mycorrhizal fungi. Mycorrhizal fungi access
and transport water - plus nutrients such as
phosphorus, nitrogen and zinc - in exchange
for carbon from plants.
Some of this soluble carbon is also channelled
into soil aggregates via the hyphae of myc-
orrhizal fungi and can undergo humication,
a process in which simple sugars are made
up into highly complex carbon polymers. The
soil conditions required for humication are
reduced in the presence of herbicides, fungi-
cides, pesticides, phosphate and nitrogen fer-
tilisers - and enhanced in the presence of root
exudates and humic substances such as those
derived from compost.
Humus holds on to some essential nutrients, storing them for slow release to plants. Humus
also can surround certain potentially harmful chemicals and prevent them from causing dam-
age to plants. Because it is so stable and complex, the average age of humus in soils is usually
more than 1,000 years. The already well-decomposed humus is not a food for organisms, but
it’s very small size and chemical properties make it an important part of the soil.
Decomposition – breakdown of organic matter from a complex to a simpler form
Molecules – smallest part of a chemical compound/substance
Symbiotic relationship – a close and long term interaction between two dierent life forms or biological species
Residues - materials left after agricultural or natural processes, organic matter
Humus - is the stable, mature portion of organic matter or compost found in the soil and helps with moisture and
nutrient retention
Humication is the process of forming humus
Conventionally managed agriculture – commercial farming using agrochemicals and mono cropping
Hyphal networks – part of the vegetative growth of a fungus that resembles long branching laments or thin tubes
Rizosphere – soil zone immediately surrounding the roots.
Mycorrhiza - are types of fungi (moulds) that create a symbiotic relationship with plant roots
Polymer- a larger molecule made up of a chain or network of smaller molecules
Soluble- dissolves in water
One principle
of nature is that the
more biodiversity
there is in a system,
the healthier and more
resilient it is.
Figure 6: Mycorrhizal fungi grow very closely as-
sociated with plant roots and create networks of
laments (hyphae) within the soil
Good amounts of soil humus can reduce drainage and compaction problems that occur in clay
soils and improve water retention in sandy soils by enhancing soil aggregation.
add organic
pore structure
reduced soilborne
diseases, parasitic
improved tilth
and water
humans and other
substances harmful
biological activity
(and diversity)
Figure 7: Adding organic matter results in many changes in the soil. (From Building soils for better crops, 2009)
Organic matter increases the availability of nutrients . . .
Directly Indirectly
As organic matter is decomposed, nutrients
are converted into forms that plants can use
Cation Exchange Capacity is produced during
the decomposition process, increasing the
soil’s ability to retain calcium, potassium, mag-
nesium, and ammonium.
Organic molecules are produced that hold
and protect a number of micronutrients, such
as zinc and iron.
Substances produced by microorganisms
promote better root growth and healthier
roots, and with a larger and healthier root sys-
tem plants are able to take in nutrients more
Organic matter contributes to greater
amounts of water retention following rains
because it improves soil structure and thereby
improves water-holding capacity. This results
in better plant growth and health and allows
more movement of mobile nutrients (such as
nitrates) to the root.
Turning air into soil
The process whereby carbon dioxide is converted to soil humus has been occurring for millions
of years. Rebuilding carbon-rich topsoil is a practical and good option for productively removing
billions of tonnes of excess carbon dioxide from the air. When soils gain in carbon, they also
improve in structure, water-holding capacity and nutrient availability.
The formation of healthy soil requires photosynthesis to capture carbon dioxide in green leaves.
Plants use energy from the sun, carbon dioxide from the air and water and minerals from the
soil to make up their food. Food is usually made in the green parts (often the plants leaves).The
process of making food using chlorophyll and sunlight is called photosynthesis. When plants
photosynthesize and make carbohydrates in their chloroplasts, they use some of those com-
pounds for their cells and structure, and some they burn for their life energy. But they “leak” or
exude a signicant amount of these compounds as “liquid carbon” into the soil. Microbes use
this energy to create complex stable forms of soil organic matter, or humus.
One of the more remarkable
things that soil scientists are
learning about plants and
soil organisms is that they
seem to have co-evolved in
a mutually benecial rela-
tionship. As we have learned
more about soil biochem-
istry we have discovered
that, through root exudates,
plants are able to control
their local environment – to
regulate the local soil mi-
croorganisms, to cope with
being eaten by animals,
to bring distant nutrients
closer, to alter the chemical
and physical properties of
nearby soil, and to inhibit
the growth of competing
The zone of soil around
the roots (the rhizosphere)
provides an ideal habitat
and good supplies of ener-
gy-rich organic matter. In
return, microbes around
the root release nutrients
and plant-growth promoting
compounds, while at the
same time providing a level
of suppression against plant
pathogens. As microbial
activity increases, the con-
version of soil organic matter to humus increases which also results
in carbon sequestration. The formation of gum and polysaccharides
by microbes and earthworms promotes the formation of stable soil
aggregates and increases the ability of the soil to retain plant-availa-
ble water and nutrients.
CEC – Cation exchange capacity (is the total capacity of a soil to hold exchangeable cations (Positively charged parti-
cles). It inuences the soil’s ability to hold onto essential nutrients and provides a buer against soil acidication.
Micronutrients Those nutrients or plant foods needed in very small amounts
Topsoil - is the upper layer of soil (usually 5-20cm deep). It has the highest concentration of organic matter and mi-
croorganisms and is where most of the Earth’s biological soil activity occurs.
Photosynthesis – is a process used by plants and other organisms to convert or change light energy from the sun into
chemical energy or sugar
Chloroplast – These are small structures inside plant cells which work to convert light energy of the Sun into sugars
that can be used by cells.
Chemical - is a substance composed of certain and specic elements, building blocks or parts
Exudate - is the emission, expulsion, sweating or oozing of a uid from one substance into another
Light energy
Figure 8: Photosynthesis
20-40% of the sugars
produced by plants
are exuded thorugh
their roots to the
Figure 9: The Nutrient cycle.
All the goodness (nutrients) from fruits, leaves, branches, whole plants, animal manure
and dead animals decompose and go back into the soil. The nutrients are taken up by
plants in the soil, with the help of microbes and in this way are recycled (used again
and again). The life of a plant is therefore a cycle and nothing is ever wasted.
Characteristics of healthy soil
Thecomplex interaction between the physical, chemical and biological properties of the soil has
a major inuence on soil fertility and health.
Although creating a healthy soil is mostly a biological process, it is inuenced by the interac-
tions that occur between the physical, chemical and biological components of the soil. Biologi-
cal activity is driven by temperature, and requires appropriate levels of air, water and suitable
nutrition. The physical properties of the soil will aect air and water exchange, which will inu-
ence biological processes such as respiration. This in turn will inuence the ability of soil organ-
isms to decompose organic matter and release nutrients for uptake by plants. The activity and
diversity of soil organisms is also inuenced by soil chemistry e.g. pH. The growing plant, and
more specically the activity of roots and material released from roots (exudates etc), also plays
a signicant part in maintaining microbial activity.
goes round
and round in a
leaves (and
other plant
and animal
break down
Water and air
penetrate soil
Minerals and
other nutrients
released into
Rocky subsoil
Plant growth
Rocks broken
Figure10: Soil Health depends on physical, chemical and biological characteristics
Physical components
The physical properties of soil are determined by the balance between sand, silt and clay
particles, which determines soil texture. These particles combine with various forms of organic
matter to form soil aggregates. The size and distribution of these aggregates through the soil
prole determines soil structure, which inuences soil stability, erosion risk, ease of cultivation
and compaction. Soil structure directly aects the movement of air and water through the soil
prole, which in turn aects biological activity, root development, crop establishment and toler-
ance to environmental stress.
Chemical components
The mineral content of the underlying soil parent material has a major inuence on soil chem-
ical properties of the soil. Of particular importance from a soil health perspective is the impact
that soil chemistry has on the development of plant-microbe interactions. For example, soils
that are based on limestone have a tendency to be rich in calcium, andto also be also alkaline,
which can restrict the uptake of nutrients such as phosphorus and manganese.
This in turn can reduce root mass and root exudate production, restricting both microbial activi-
ty and plant response to microbial growth promotion. Soil pH inuences microbial populations,
encouraging bacteria to dominate alkaline soils and fungi to dominate acidic soils. A better
balance of bacteria and fungi can be found at more neutral soil pH values. Bacteria require sim-
ple sources of soluble organic matter and have high multiplication rates, while fungi can utilise
more complex insoluble forms of organic matter and have relatively low multiplication rates.
Biological components
During its conversion from plant and animal residues to humus, soil organic matter has a direct
impact on soil health. Un-decomposed organic material provides a food source for macro-or-
ganisms such as earthworms.
Respiration – breathing of plants
pH – an indiction of how acidic or alkaline a soil is.
Chemical – structure, composition and properties of substances
Compaction – compressing of soil particles into a more dense mass
Mineral – An inorganic substance in naturethat occurs naturall in rocks nad the soil
Earthworms mix partially decomposed organic
matter with soil minerals as the material pass-
es through the gut, creating channels for air
and water movement as they go.
Microbes thrive in the earthworm casts,
completing the conversion of organic matter
to plant-available nutrients and humus. This
humus can bind sand, silt and clay into stable
soil aggregates, while at the same time provid-
ing exchange sites for nutrients and improving
water retention. This results in increased soil
fertility and yield potential.
Soil composition
What is soil?
Soil contains abundant plant and animal life,
as discussed above. There are four main
components of soil: mineral matter, organ-
ic matter, air and water. Soil minerals are
made through the breaking up of the basic
elements or minerals of the earth. These are
initially found in the form of rocks or ‘parent
material’. Over a very long time, these rocks
are broken down into small particles through
rain, wind, sun and soil organisms and mixed
with air and water. This becomes soil that can
support plants and micro-organisms to grow.
Like people, plants cannot live and grow with-
out water, air and food.
The mineral matter (45%) is made of sand, silt
and clay size particles—the basic texture of
the soil. The soil water (25%) con-
tains dissolved minerals and is
the main source of water and
nutrients for plants. The air
(25%) in the soil is needed
for plant roots and soil
microorganisms to obtain
oxygen. Organic matter
(5%) includes plant and
animal materials in various
stages of decomposition and is
discussed above.
Figure 11: An earthworm in a clod of soil showing the
soil channels, earthworm casts and soil aggregates.
(From H.Smith, 2015)
Figure 12: A typcial soil prole
(From: FARMESA2003. A study guide for FFS. Soil and water conservation.)
material breaking
down to form 1 cm of
soil can take between
200-1 000 years
Characteristics of soil texture types
Sandy soil
Good things about this type of soilBad things about this type of soil
ÄIt is easy to dig and work with
ÄIt warms up quickly in spring after winter
ÄIt is good for root crops
ÄWater and air can get into the soil easily
ÄIt gets dry quickly
ÄIt does not keep much fertility
ÄIt does not hold water well
Loam soil (Mixture of sand and clay)
Good things about this type of soilBad things about this type of soil
ÄHolds water well
ÄBest for root growth
ÄContains organic matter, like …..
ÄThis soil can be hard when dry
Clay soil
Good things about this type of soilBad things about this type of soil
ÄHolds water well and for a long time
ÄHolds fertility well and for a long time
ÄHard to work; heavy
ÄSlow to warm up in spring
ÄSticky when wet
ÄHard when dry
It is important to know which soil type you have. Crumbly and loose soil holds the most water
and the most air, which is what plants need to grow. To make your soil more crumbly (whether
it is sandy, loam or clay) you need to keep adding lots of manure, compost and mulch. Never
walk on the planted areas, especially if they are wet.
All types of soil need organic matter to increase their fertility, or plant food. Sandy soil needs to
be given organic matter to increase its ability to hold water and plant food or nutrients. Clay soil
needs to be given organic matter to increase its ability to hold air in the soil and to release the
plant foods that are there.
ÄSand makes the soil loose.
ÄSilt is very ne sand. It holds water and plant food better than rough sand, but it is easily
washed out of the soil.
ÄClay is the sticky part of the soil that holds it together. It holds water like a sponge.
The best soils according to texture class are called loams and they are an equal mixture of
sand, silt and clay.
How to tell your soil texture type
You can tell how much sand, silt or clay (commonly called texture) is in your soil by how it feels.
Wet some soil and roll it into a ball between your hands. Then roll this little ball into a sausage.
Below is a table that describes how you can tell what type of soil you have.
What soil looks
What soil feels
When rolled into a sausageThe soil is ...
Very sandyVery roughCannot be rolled
into a sausage
Very sandy
0-5% clay
Quite sandyRoughCan be rolled
into a sausage,
but it cannot
5-10% clay
Half sandy and
half smooth
RoughSausage can
bend a little
Sandy loam
10-15% clay
Mostly smoothA little sandy,
quite smooth,
but not sticky
Sausage can
bend about half
way round
Loam or silt
15-35% clay
Mostly smoothA little sandy,
quite smooth
and sticky
Sausage can be
bent more than
halfway round
Clay, loam or
sandy clay
35-55% clay
SmoothSmooth and
Sausage can
bend into a ring
More than 55%
Another method of identifying the proportion of soil
participles in a soil is to conduct a “bottle test”.
To do this, take a bottle and ll a third of it with soil.
Pour water into the bottle until it is almost full, place a
lid on and shake it vigorously for a few minutes in order
to separate the soil particles. Leave the bottle to settle,
and note what happens over the next few hours. You
will see that the substances settle in layers, the heaviest
at the bottom and the lightest on top.
The layer of water above the settled material remains
cloudy for a long time because it contains clay parti-
cles which are so small that they stay suspended in the
water. Substances which are lighter than water (organic
matter like leaves, seeds, spores, and insect and animal
waste) oat on the surface.
Heavy particles such as gravel, pebbles and sand fall
quickly to the bottom of the bottle. The ner elements
then accumulate – rst the silt, followed by humus and
then the ne and very ne clay. These layers vary in
colour and consistency.
organic matter
cloudy water
with very ne
clay particles
very ne clay
ne clay
sand and ne
gravel and pebbles
Figure 13: Bottle test showing proportion
of soil separates (From: WHC Manual, WRC, 2010)
Soil structure
Soil structure describes the grouping or arrangement of primary particles (sand,
silt, clay and organic matter) into larger, secondary particles called aggregates.
It is the shape that soil takes, determined by the way in which individual soil
particles clump or bind together.
Aggregates are the fundamental unit of soil function and play a role sim-
ilar to that of root nodules in legumes, creating a protected space. The
aggregate is helped to form by hyphae of mycorrhizal fungi that create a
“sticky-string bag” that envelops and entangles soil particles. Liquid carbon
exudates from plant roots and fungi enable the production of glues and gums
to form the aggregate walls.
Inside those walls a lot of biological activi-
ty takes place, again fuelled by the carbon
exudates. Most aggregates are connected
to plant roots, often ne feeder roots, or to
mycorrhizal fungal networks too small to be
seen. The moisture content inside an aggre-
gate is higher than outside, and there is lower
oxygen pressure inside. These are important
properties enabling nitrogen-xation and oth-
er biochemical activities to take place.
Soil structure aects the movement of water
and air in the soil, as well as root penetration
and biological activity. For example, a dense
structure greatly reduces the amount of air
and water that can move freely through the
soil and it is dicult for roots to penetrate
such soil.
Figure 14: Using the bottle test to estimate the proportion of soil components in a sample
Figure 15: The dispersed soil participles are clumped
together into aggregates
Microbial and fungal byproducts
glue the particles together
organisms play an
important role in soil
aggregate formation
and structure.
Identication of Soil
The structure of the surface
layer of the soil is usually weak
to strongly granular or blocky,
but a degraded surface layer can
be crusted, platy, or structure-less
(massive or single grained). This
is important as soil crusting
reduces water and air inl-
tration, destroys soil life
and increases run-o and
Figure 18: The dierent structures
that soil can take
Figure 16 (above): Soil aggregates are groups of soil particles that are glued together by microbial and fungal
by products. Very small aggregates group together to form larger aggregates
Figure 17: Roots, fungal hyphae,
and their secretions stabilize soil
aggregates and promote good
soil structure, thus preventing
aggregates protect
the soil against
wind and water
The more soil organic matter (SOM) there is in the soil, the more macro-aggregates can form
and the better the soil structure becomes.
Soil Degradation
Degradation most commonly occurs when erosion and decreased soil organic matter levels
initiate a downward spiral resulting in poor crop production. Soils become compact, making
it hard for water to inltrate and roots to develop properly. Erosion continues and nutrients
decline to levels too low for good crop growth.
Tillage or ploughing usually starts this degradation process. Fields that have been ploughed a
lot tend to crust, seal and compact more than non-till elds with lots of crop residues and a liv-
ing plant cover with active roots and fungi. Tillage also reduces inltration and the water hold-
ing capacity of the soil due to poor structure and thereby increases water run-o and erosion.
(b) Soil seals and crusts after
aggregates break down
Figure 20: Changes in soil surface and water-ow pattern when seals and crusts develop
Figure 19: (Left) The dierence in colour and structure caused in a soil by increasing the soil organic matter.
(Right) Cover crops growing through a thick layer of organic matter.,https://iowaenvironmentalfocus.les.wordpress.
(a) Aggregated soil
It can also reduce the germination of seeds and root growth. It makes the soil a lot more prone
to wind erosion when it is dry.
Centre for Food Safety, 2015. Soil and Carbon: Soil solutions to Climate Problems.
Cooperband, L., 2002. Building Soil Organic Matter with Organic Amendments. A resource for
urban and rural gardeners, small farmers, turfgrass managers and large-scale producers. Uni-
versity of Wisconsin-Madison, Center for Integrated Agricultural Systems.
Jones, C., 2015. SOS - Save Our Soils, Acres USA, Vol. 45, No. 3
Kittredge, J., 2015. Soil Carbon Restoration: Can Biology do the Job? Northeast Organic Farming
Association / Massachusetts Chapter, Inc.
Magdo, F. and Van Es, H., 2009. Building Soils for Better Crops. Sustainable Soil Management
series, 3rd Edition, SARE Handbook Series, Book 10.
A dust storm on the farms around Bloemfontein in
the Free State in October 2014
(From: GSA, 2015)
Soil crusting caused by ploughing and breakdown of
soil structure
intensive tillage,
soil erosion, and
insucient added
break down
increased erosion
by wind and water
hunger and malnutrition result
crop yields are reduced
more soil organic matter is lost
surface becomes
compacted, crust forms
soil organic
matter decreases
less soil water
storage, less
diversity of
soil organisms,
fewer nutrients
for plants
Figure 21: The downward
spiral of soil health due
to intensive tillage or
continuous ploughing
Conservation Agriculture
Conservation agriculture (CA) aims to conserve, improve and make more ecientuse of soil,
water and biological (e.g plants, animals, insects and microbes) resources.
Basic principles of conservation agriculture
CA is based on the following three principles that should be used SIMULTANOUSLY:
ÄMinimum mechanical soil
disturbance: the soil is not
ploughed! The seeds are planted
directly into a mulch covered eld
using specialised no-till planters.
 Womenplantingaeldcoveredwith
ÄPermanent organic soil cover
(mulching): The crop residue is
left on the eld, mulching is intro-
duced or a cover crop is planted.
 ACAmaizeeldwithcropresidueinto
(from H Smith, GSA, 2015)
ÄDiversied cropping (Including
cover crops): It is important to
mix (intercrop, and diversify) and
rotate the crops to reduce weeds,
control pests and diseases and
improve soil fertility.
 Aeldintercroppedwithbeansand
lines(from Mahlathini Organics, 2015)
The application of all these CA principles then makes it easy to follow other good agricultural
practices, such as:
ÄIntegrated soil fertility and acidity management: CA improves soil fertility and thereby
reduces the amount of fertilizer required and saves time, money and energy. It is possible
to have a sustainable biological system without the use of fertilizers.
ÄIntegrated weed management: CA reduces the need for herbicides over time. It is possible
to have complete weed control without using chemicals.
ÄIntegrated pest and disease management: Management of pests and diseases includes
crop diversication, timing of planting, promotion of natural balances between pests and
predators in insects and naturally occurring microbes as well as physical control methods.
This reduces the need for expensive pesticides and fungicides to a minimum.
ÄIntegration of animals: Systems that in-
clude fodder production and management
for livestock create an added benet. This
practice can include winter and summer
forage crops such as Dolichos, sunnhemp,
fodder rye, black oats, fodder radish and
hairy vetch, as well as longer term grass
species. Besides improving the physical,
chemical, biological and water holding
properties of the soil, such species, includ-
ing annual or perennial cover crops, can
successfully be used as animal feed.
Minimum tillage and zero tillage are techniques within CA that point towards the amount of
disturbance of the soil. For zero tillage the soil is disturbed only where the seed is planted. For
minimum tillage there may be lines ripped or small basins dug for planting of seed. The whole
eld is NEVER ploughed.
Disturb the soil as
little as possible
Mix and
Keep the soil covered as
much as possible
An example of minimum tillage
using an oxen drawn Magoye
ripper, which just makes a small
furrow where the seeds will be
planted. The rest of the soil is not
ploughed or turned over.
(From: FARMESA 2003. Study guide for FFS.
Soil and water conservation. SIDA)
Repeated ploughing, use of excessive chemical fertilisers, herbicides and
pesticides and mono cropping has led to a number of negative
impacts on the environment including:
ÄA decrease in the organic matter of the soil
ÄBreak down of biological, physical and chemical proper-
ties of macro aggregates in the soil leading to
– Crust formation and compaction
– Wind and water erosion and loss of topsoil and
– Fewer soil organisms, lower soil fertility and
– Reduced water inltration and content
ÄIncreased amount and costs of fertilizers and other agro
Minimum Soil disturbance
The idea is to disturb the soil as little as possible; to till the soil only where the seed and fertility
amendments (fertilizer, manure, compost) are to be placed.
Disturbing the soil as little as possible has the
following benets:
ÄIt ensures minimum destruction of the soil
ÄIt does not expose soil to wind and water
ÄIt allows slower mineralization of organic
matter, hence organic matter build-up.
ÄIt causes little disruption to the life of
organisms that reside in the soil, which
improve the soil structure
ÄIt saves on time, energy and money as
there is less ploughing and fertility amend-
ments are placed only in the planting
Fertilizer leads to
less water, less air and
less life in the soil. Then
more fertilizers, pesticides
and other chemicals need to
be added to compensate for
this and keep crops
The pictures on the right show some minimum soil
disturbance options for smallholder farmers. Note
that the area between the planting basins and rip
lines is not disturbed and that the soil is covered by
a mulch formed from crop residues. The picture at
the top shows planting basins prepared using a hand
hoe. In the picture below, rip lines are prepared
using a ripper tine, with seed and fertilizer boxes
attached to the beam of a standard animal drawn
Soil cover
The soil needs to remain covered either with
crop residues, other types of mulch or grow-
ing plants at all times. Generally in CA the
crop residue is left on the eld to cover the
soil. Other types of mulch can also be placed
between the rows and planting basins or
planting holes.
Mulch not only reduces soil erosion, it can re-
duce soil temperature by at least 4°C, creating
better conditions for soil organisms to thrive.
When properly managed soil cover has the
following benets:
ÄIt improves water inltration resulting in a
higher soil water content
ÄIt helps in reducing direct raindrop impact
and run-o in the eld; thus reducing soil
ÄIt reduces evaporation and conserves soil
ÄIt keeps the soil temperature even and
ÄIt helps to suppress weeds
ÄIt provides for food and a conducive
environment for soil organisms that are
important for biological processes and soil
Mix and rotate crops
As we are aiming to mimic nature, we want
to create as much diversity in our elds as
possible. Diversity ensures a natural balance
in the eld. This includes creating a living
soil, protection against weeds, using water
eciently and minimising pest and disease
attack on crops.
Biodiversity on top of the soil equals biodi-
versity below the soil, which includes the
presence of living roots in the soil for the
entire year. Maximum cover on top of the
soil by plants either living or dead serve as
armour to the soil just as our skin protects us
from the sun and the rain. It keeps the soil
cooler in summer and warmer in winter. This
all leads to the build-up of carbon in the soil,
which is vital for our farm’s sustainability. For
every 1% of added carbon to the soil, the
water holding capacity of that soil doubles.
Above and below:Soilcoverprovidedbymaizestover
beans(from H Smith, 2015)
Mixed cropping involves planting various crops together in one plot. Plants can either be inter-
planted at the same time (inter-cropping) or crops can be rotated. This means that dierent
crops are planted in the same place at dierent times. Using both inter-planting and crop rota-
tion in your eld is a good idea.
In this system food crops are mixed with soil enriching crops that
Äcan x nitrogen into the soil (legumes) and cycle plant nutrients
Ägrow fast and provide a lot of above-ground (leaf) and below-ground (root) biomass and
Äimprove soil biology, soil fertility and soil structure both when they are growing and when
they are decomposing in the soil.
These crops are called cover crops. Generally they would also have other benets as food
crops for people and or livestock.
Mixed cropping has the following benets:
ÄSoil fertility replenishment – N-xing legumes add ‘top-dressing fertilizer’ to the soil.
ÄCrops better use the nutrients in the soil. Dierent crops have dierent feeding zones and
will therefore not compete for nutrients. The exploitation of dierent soil layers by dierent
crops also helps prevent formation of a hard pan.
ÄIt helps to control diseases and pests as the life cycles of these pests and diseases are bro-
ken by the introduction of a dierent crop
ÄThe soil structure benets when the soil is occupied by the roots of many dierent plants,
because –
– the roots move the soil;
– the roots create a network of living matter which dies and rots to create humus;
– when the roots die they leave tunnels which improve the porosity and drainage;
– roots secrete weak acids to dissolve minerals in the soil then draw these back up in solu-
– roots also secrete a portion of their photosynthetic energy in the form of sugars that feed
the microbes, which in turn provide soil mineral nutrients to the roots.
When crops are planted in the same place at dierent times it is called crop rotation.
Above: A plot of maize and
beans that have been planted
as an intercrop. Both crops are
growing well and there is no weed
Above: Two intercropped plots (In Bergville area, 2014). Maize
and beans are planted together on the left and maize and
cowpeas are planted together on the right of the picture.
The maize on the left is slightly smaller and yellower than the
maize on the right. The beans are also slightly yellower. This
shows that the cowpeas add more nitrogen and provide more
nitrogen for growth of the maize than the beans. Growth is
generally very good.
An example of intercropping
Maize can be planted together with legumes such as beans
or cowpeas and pumpkins. This process has many benets,
including addition of nitrogen to the soil, soil water conserva-
tion and weed suppression.
An example of crop rotation
pamphlets/no-till-pamphlet-july-2014.pdf: A case study of no till
production by Tony da Costa of Manjoh Ranch, Nigel SA)
When using rotations it is best to have at
least three dierent crops. A good rotation
that will also provide fodder for livestock is to
plant maize in season 1 (October-November)
followed by a winter cover crop of black oats
the next winter in February-March (which is for
grazing), followed by soya beans the next year
(October-November). Bergville grainSA SFIP, 2014
When crops are planted in the same place at dierent times it is called crop rotation.
How to implement
Conservation Agriculture
There are a number of dierent planting
systems within conservation agriculture (CA).
The choice depends largely on how much
land you plan to cultivate and your access to
no-till planting equipment and labour. It also
depends a lot on the type of soil you have and
the cover on top of the soil.
The three main systems are:
ÄHand planting
ÄAnimal drawn no-till planters and
ÄTractor drawn no-till planters
CA is a process of moving away from a high
external input system towards a low external
input system. We are aiming to maximise
yields while using as little herbicides, fertiliz-
ers and pesticides as possible. The success of
reaching our aim will depend largely on the
quality of implementation of the three CA prin-
ciples: a) not ploughing or disturbing the soil,
b) keeping the soil covered with organic mate-
rial or mulch, and c) the use of crop rotations
and cover crops.
When we start to do CA it may take a while for
the system to balance or to work well and for
crops to grow well. In the rst few years there
are likely to be some problems with weed in-
festation, lack of organic matter in the soil and
soil infertility issues, including acidity in the
higher rainfall areas.
On smaller plots it is easy to introduce mulch
to reduce the weed competition and this works
for eld crops as well as vegetables. On larg-
er plots, while this is still possible, we usually
spray herbicides on the eld to kill weeds be-
fore and at planting, as well as after planting.
As the ground cover increases and the weed
seed stocks/ reserves in the soil decreases,
less and less herbicide will be needed. The aim
is to get to a point where no herbicide will be
Above: A plot of cabbages planted using the no-till
method. Note the mulching that stops weeds from
growing. From: Mr Simon Hodgson, Cover Crop Solutions, 2014
Reducing weeds by intercropping
Single planted plots have more weeds,
because of the space between the rows of
plants. Intercropped plots form a canopy
that covers the soil a lot more quickly than
single crop plots. This suppresses further
weed growth.
Intercrop plots, with close spacing of crops
may require only 1 weeding, or under ideal
conditions no weeding at all. Single crop
plots require 2-3 weedings in the season.
Left: A plot of beans where weed competition
has reduced the growth and plants are yellow-
Right: A maize and bean intercropped plot
showing the lack of weeds and good growth of
both plots.
(Pics from GrainSA SFIP, Bergville 2014)
Timely Preparation and Planting
Preparing the elds and planting in time is very important.
Land preparation
for hand planting
NOTE: We have given very general
recommendations for quantities
of manure and fertilizer, based on
a summer rainfall area of 700-800
mm rain per year with clay-loam
(20-30% clay in topsoil) soils that
tend towards being acidic. The
maize yield target for this specic
example is 4-8 ton ha-1yr-1 Maize
plant populations could range be-
tween 40,000 to 70,000 plants per
What operation? When?
Land Preparation (digging basins, ripping,
digging furrows)
July – October
Pre planting spray of herbicidesSeptember- October (2 weeks before plant-
ing and at planting)
Application of basal fertility amendments
(manure, compost, fertilizer*, lime)
October- November (at planting or 2 weeks
before planting)
Planting; spray pesticide (cutworm and stalk
borer), single crops and intercrops
October -November
First weeding and relay planting of legumes
as intercrop or cover crop
As soon as weeds appear, 1-2 weeks after
Second weeding and top dressing; check for
stalk borer and spray pesticide if required
(5% shot hole damage on maize leaves)
December-January, just before top dressing
(4-6 Weeks after planting)
Relay crop planting of winter cover crops
and nal weeding. Watch for pest damage
during tasseling and cobbing and spray
pesticide if required
February- March
Harvesting May-June
Post-harvest management June-July
*consider eco-friendly fertilisers where possible
Planting basins
Seeds are planted not along the usual furrow but in small basins or pits that can be dug with
hand hoes without having to plough the whole eld.
Step 1: Prepare basins [July–October]
ÄRemove weeds from the previous season
ÄDig basins 15cm long x 15cm wide x 15cm deep
ÄBasins should be arranged in rows. Basin spacing is 60cm in the row and 90cm between
rows. A spacing of 75cm X 75cm can also be used.
Step 2: Add manure [Sept–Oct]
ÄApply 5-10 handfuls or one spade full of manure/compost in each basin and cover lightly
with soil. If lime is being applied mix it in with the manure. Apply ½ food tin (250g) per basin.
This is equivalent to 1ton/ha.
ÄIt is good to apply manure and lime some time before planting to allow these slow acting
compounds to start working.
Above: (left) Adding manure to a basin and (right) adding lime to the basins using a matchbox.
The type and
amount of fertilizer is
specific for your field. If you
do not have a soil sample
result to work from there are
general rules of thumb
one can follow for
your area.
Step 3: Planting [November–December]
ÄPlant after good rains, when the soil is damp but not
too wet and sticky.
ÄIf fertilizer is being applied, apply 1 level cool drink
bottle cap or teaspoon per basin of MAP (around
4,2g/basin). Place this to one side of the hole and
cover lightly with soil rst before placing the seeds
in the basin
ÄPlace 3 pips (seeds) in each basin
ÄCover the seeds with soil
Right: Adding one bottle top of fertilizer per basin
Step 4. Weeding & thinning
Ä1st Weeding: as soon as weeds start
ÄThinning: 2-3 weeks after germination,
leaving 2 plants per basin
Ä2nd weeding: 4-6 weeks after crop
Step 5. Top dressing with limestone ammonium Nitrate (LAN)
ÄApply LAN at 5-6 leaf stage; Use half a cool drink bottle cap or half a teaspoon full per basin
of LAN (2,5g/basin).
ÄDo not broadcast the fertilizer – apply it carefully near the base of each plant. In this way, all
the fertilizer goes directly to the plant, nothing is wasted. Only apply fertilizer to moist soil –
not dry.
Step 6. Harvest [March–July]
ÄRemove cobs and leave stalks standing in the
ÄCut stalks at the base
ÄSpread the cut stalks in the eld, between rows
Step 7. Management in dry season
ÄRemove weeds that are still in the eld
ÄPrepare basins in the same positions as last sea-
son and start all over again!
Top dressing with half a
teaspoon of LAN per basin.
weeding can
increase your
yield by 50%
Shallow planting furrows
This CA system uses a hand hoe and again you do not have to plough the eld before planting.
Like the planting basins, land preparation is best done before the onset of the rainy season
from July to October.
Step 1. Prepare furrows
ÄRemove weeds from previous season
(either mechanically or chemically)
ÄDig furrows 5-10cm wide and approx-
imately 2-5cm deep. Spacing depends
on the planting system used. Space
rows 50cm, 75cm or 90cm apart for
maize. If the rows are spaced wide
apart then more plants can be placed
in the rows; for example one can use a
90cm between-row x 40cm in-row plant
spacing, or one can plant in a square
grid of 50cm between x 50cm in row
spacing. For beans an in-row spacing of 10cm is used with 25cm,
30cm or 50cm between rows.
NOTE: The closer (denser) plants are to each other, the more they pro-
tect the soil and suppress weeds
Above: Lines of string have been placed to indicate the spacing for furrows – here
25cm for two rows of beans and 50cm for 2 rows of maize.
Step 2. Add manure
ÄApply 2 spades -full of manure or com-
post per meter of row
ÄIf lime is being applied mix it in with the
manure. Apply 1 food tin (500g)) per
metre of row.
It is good to apply manure and lime some
time before planting to allow these slow
acting compounds to start working
Right: Applying lime in the planting furrows
Step 3. Planting
ÄPlant after good rains
ÄIf basal fertilizer, such as MAP is availa-
ble, apply 2 level cool drink bottle caps
or ½ of a matchbox per meter of row.
ÄPlace seeds 10cm-50cm apart in the
rows, depending on whether you are
planting legumes or grains
ÄCover the seeds with soil
It is easier
to weed when
crops are planted
further apart, but it is
also easier for the
weeds to grow.
Step 4. Weeding [December–February]
Ä1st weeding is done as soon as weeds start emerging
Ä2nd weeding is done around 4-6 weeks after crop emergence
Step 5. Top dressing with limestone ammonium nitrate
ÄApply LAN at 5-6 leaf stage; Use a quarter of a cool drink bottle cap or a quarter of a tea-
spoon full per plant of LAN (1,25g/plant). For beans you can use about half of this recom-
mendation as they make their own Nitrogen and adding to much fertilizer can favour leaf
growth over seeding.
ÄDo not broadcast the fertilizer –apply it carefully near the base of each plant.
Step 6. Harvest [March–July]
ÄRemove cobs and leave stalks standing in
the eld
ÄCut stalks at the base, atten or leave
ÄSpread the cut stalks in the eld, between
remains. A relay cover crop is germinating through this
Step 7. Management in dry season [June–Sept]
ÄRemove weeds that are still in the eld
ÄPrepare the rows in the same positions as last season and start all over again!
Tramline intercropping
This is a CA system of spacing eld crops in an intercropping system that minimises potential
competition for light, water and nutrients, optimises the use of available land surface and max-
imises production. This can be done using hand or animal-drawn planters.
Ä2 Rows (tramlines) of maize are planted 75cm apart with an in-row spacing of 30cm
ÄThen, in the 1.5m spacing between tramlines of maize, 2 rows of legumes are planted; with
50cm between rows and 3-5cm in row spacing.
ÄPumpkins can be spaced evenly along the tram line of maize at a reasonably low density to
avoid crowding.
weeding can
increase your
yield by 50%
It is possible to use a close spacing system with tramlines as well. The idea is to plant the crops
as close together as possible so that crop canopy forms early in the season reducing the need
for weeding. Here the two rows of maize are planted with a spacing of 50cm between and 25-
50cm in row spacing (depending on the desired plant population) and the two rows of beans
are planted with a 25cm between row and 10cm in row spacing.
For this tramline system a mixture of basins and rows can be sued, where basins are prepared
for planting the maize and beans are planted in rows in between the maize basins.
Using hand planters
No-till hand planters are designed to make small holes or openings in the soil and deliver either
just the seed or seed and fertilizer into these holes. This leads to an absolute minimal distur-
bance of the soil and also decreases the labour needed for planting signicantly.
There are a few dierent designs of hand planters that can be tried out and that are available.
Some examples are shown below.
The Haraka hand planter
The Haraka planter shown here is a
hand pushed rolling or rotating no-
till punch planter that places seed
of dierent kinds of crops includ-
ing maize, beans and small seeded
crops like cabbages, sorghum and
cover crops 30cm apart in the row
as it is being pushed. Fertilizer, if
being applied, is placed on top of the soil next to the seed after
planting. The Haraka planter is adapted for both sandy and
clay soils. For clay soils, to assist in soil penetration to 4,5cm
planting depth, weights can be added to the side of the wheel.
It is suitable for planting small to medium sized elds between 0.5 and 5 ha. The planter is cur-
rently one of the fastest type of hand planting tools and is supplied through Growing Nations
and Eden Equip (
The MBLI hand planter
Afritrac ( the Mealiebrand MBLI hand planter. This works similar-
ly to a hoe and places both seed and fertilizer in two small holes alongside each other. Seed
is placed in the hollow pipe handle of the planter and fertilizer is carried in the small pouch
carried on the planter’s back. Seed plates are available for a number of dierent seed types
including maize, beans and smaller seeded grains such as sorghum. This planter is easy to use
and adapted for sandy to medium high clay soils. It is most suitable for small elds up to 1ha in
The Matraca jab
The Matraca planter, a
well-known jab planter
imported from Brazil,
supplies both seed
and fertilizer alongside
each other in two small
holes at planting.). It is
pushed into the ground
and then pulled open
like a lever or pair of
scissors to release the
seed and fertilizer. It is well adapted to sandy and clay soils, but needs reasonable arm strength
to handle well. It is suitable for small elds up to 1ha in size. It is currently supplied by Inntrac
Trading (
Animal drawn planters
There are various types of animal drawn planters
to use in CA systems. The rst option is to only use a
ripper to open furrows into which fertiliser and seed are
manually (by hand) placed and covered by soil (see photo).
Right: Animal drawn ground ripper (from
The second option is a complete animal drawn no-till planter
that is designed for seed and fertilizer placement in the furrow
made by a ripper tine attached to the planter. A basic and cheap version, modied from the
well-known Sam planter, is oered by Afritrac (
The Napick planter, imported from Brazil, is
a more sophisticated animal drawn planter,
but costs considerably more. Because of the
springs and wheels on this planter, it is much
easier to turn at the edges of the eld.
A combination of agronomic (mulching, mixed cropping, cover
crops and crop rotation), chemical (herbicides) and mechanical
(hand hoeing) methods of weeding can be used, depending on
how serious the weed problem is and whether the chemicals
and equipment can be obtained.
Advantages of chemical
weed control
Herbicides allow us to control
weeds and reduce the number of
tillage operations as well as the
critical timing needed for opera-
tions. This has allowed the wide-
spread adoption of CA practices.
Herbicides reduce the amount of
human labour necessary.
Disadvantages of chemical
weed control
Injury or damage to non-target
species, crop injury or damage,
herbicide carryover, weed resist-
ance, container disposal problems
and more recently, surface and
groundwater contamination and
the associated potential health
risks from human exposure are
risks. Another risk is poisoning
from the actual application of the
herbicides, if it is not done cor-
A high degree of technical knowl-
edge and skill is required for
eective utilization of chemicals.
Safety measures should always be
used with chemical weed control.
Right: It is important to wear the
necessary protective clothing – to wear
goggles, a mouth and nose ventilator or
mask, gloves, gumboots and a protective
of goggles, gloves and boots should be
worn at all times.
One of the
most important
benefits smallholder
farmers want is for cover
crops to control weeds.”
- Roland Bunch
Using herbicides in Conservation Agriculture
Apply non-selective herbicides using a knapsack sprayer 2 weeks prior to soil preparation and
planting. Apply the pre-emergence herbicides at planting.
Spraying herbicides
Start with a non-selective herbicide that will kill both grasses and broadleaf weeds. Glyphosate
is one such herbicide and it is commonly known by the name of Roundup (produced by the
Chemical Company Monsanto). It is generally used at a rate of 2-4l/ha, depending on the type
and severity of weed infestation. This means that you will put 200-320ml of Roundup in each
16l of water to ll up a knapsack sprayer.
The speed at which you walk and the speed at which you pump the handle of the knapsack
sprayer will determine how much of the herbicide you are spraying onto an area of ground.
As a general rule the lever is pumped 1x every second. So if you walk at a steady pace (not fast
and not slowly), spraying with the nozzle at knee height and recite the word ‘one thousand’ over
and over again making one pump stroke per ‘one thousand’ – you should be doing it almost
Mostly, an application volume of 200l/ha is recommended. To see how close you are to this rate
it is important to rst practice and calibrate your spraying rate. This can be done by marking
out an area of 10mx10m on hard dry ground. Then ll up the knapsack sprayer with 2litres of
water. The operator should be able to walk and pump at a speed that means the 2l of water will
cover the 10mx10m area.
Right and below:Itisimportanttomakesurethatthettingsareallworkingcorrectlyduringatestspray.Afa-
cilitator and new operator calibrate their walking and pumping speed and a good walking and pumping ‘rhythm’
is set up by experienced knapsack users. Note the distance of the nozzle from the ground.
Examples of pre-emergence herbicides
• Alachlor such as Lasso, Sanachlor,
• S-metolachlor + safener such as Dual
S Gold
• Acetochlor such as Trophee CS, Relay,
NOTE: These herbicides kill weeds before
they come up.
Examples of non-selective herbicides
(which kill every growing plant) are:
• Glyphosate such as Roundup, No-
plough, Mamba, Senator etc)
• Paraquate such as Gramoxone, Agro-
NOTE: These herbicides will only work if
applied to green, actively growing weeds!
Tips for spraying of herbicides
ÄWeeds should be sprayed when in active
growing stage, preferably at 4 to 10 cm in
ÄSpray in the cool part of the day
ÄDo not spray when there is dew on the
weeds, this dilutes the herbicide
ÄDo not spray when there is a wind blowing
ÄDo not spray when rain is pending
ÄUse clean water to dilute the herbicide
ÄCalibrate the sprayer before using to ensure
the correct dose is applied.
ÄWear protective clothing and use the
mouth and nose ventilator.
ÄDispose of the empty containers by wash-
ing out rst and then burying.
ÄIt is important to know whether chemicals
can be mixed together or whether they
need to be sprayed separately. Some of
this information will be given on the label
of each chemical. Some of the chemicals
react and interfere with each other, so mix-
ing them will change how they react or stop
them from reacting.
ÄOnly make up enough diluted mixture that
will be used immediately
ÄWhen working with undiluted chemicals it
is VERY important to wear the protective
clothing. All chemicals are poisonous in
undiluted form and can be taken up into
the human body through the skin and by
inhaling. Gloves and a mask are an abso-
lute minimum.
ÄStorage of chemicals in a safe, lockable area where children do not have access is very
important. Do not store the chemicals in cool drink bottles that can
be mistaken and drunk from. All containers need to be clearly
ÄCleaning and maintenance of the knapsack sprayers is also
important. After use, rinse with 3 full volumes of clean water
– and push clean water through the nozzles as well.
ÄDo not always use the same type of chemical to prevent
weeds from building-up resistance
ÄUse as many agronomic methods as possible (crop rotation,
cover crops, mulching) to gradually replace the use of chemicals
in weed control.
Above: The nozzles are at the tip of the sprayer
where the liquid sprays out. The best nozzle
It is possible
to control weeds
effectively without
herbicides IF agronomic
practices are
implemented well.
Do’s and don’ts of spraying with
Herbicides are not a solution to lack of weed
management. When your weeds are too large
there is no herbicide that will deal with the
Right: Herbicides cannot take the place of good man-
agement. If weeds have been allowed to grow too large,
herbicides cannot solve this problem.
Herbicides can also kill your crops if you are not careful. Roundup will denitely kill maize and
beans, as will Gramoxone. So once the crops are growing it is best to do hand weeding.
Above: Left – An example of crops that were sprayed with herbicide after germination – where the farmer did not
realise that the herbicides will also kill his crop. Middle; Necrotic spots and lesions where herbicide has drifted
onto maize plants when applied in between the rows (in this case Gramoxone was used) and Right: An example of
inter-row spraying of Roundup later in the season, which killed the beans that were planted there but only partial-
Herbicide spraying programmes
There are two general spray programmes that have been
tried and tested in the smallholder context. Here the assump-
tion is that the grasses such as nutsedge and couch grass will
be signicant problems.
Right: A Yellow nut sedge plant.
Roundup (Glyphosate) kills fast growing (green) broadleaf
plants and grasses. If it comes into contact with your crops
it will kill those as well. So it needs to be sprayed 1-10 days
before the crops are planted. Do not enter and work in a eld
that has just been sprayed. It needs to be left for at least 24
hours. Glyphosate does not work well or at all on plants that
are not actively growing or are old.
Gramoxone is a non-selective quick acting post emergence herbicide for brodleaves and grass-
es. Like Roundup it will kill anything it comes into contact with. It is a contact herbicide, so acts
immediately and does not build up in the plants or in the environment. It is however a lot more
poisonous to humans and animals than Roundup, especially in its undiluted form. It is partially
inactivated on contact with the soil.
Dual Gold is mainly taken up through the shoots of germinat-
ing plants and seedlings. Weeds are therefore killed before
emergence, at emergence or shortly after emergence. It is
taken up mainly through shoots, rather than roots of plants.
1. Glyphosate and S-Metolachlor:
a. Use Roundup turbo or max, 2 weeks before planting
b. If it is still too dry and the soil is bare then –
i. Spray Roundup later just after planting (just after plant-
ing (assuming there has been some rain) or
ii. Spray Roundup just before planting and Dual Gold
mixed with pesticides (Decis Forte) just after planting
2. Paraquate
a. Spray Gramoxmone 2 days to just before planting if there
is longer grass and bigger weeds (Roundup is not so eec-
tive on these) and
b. Spray Dual Gold mixed with pesticide (Decis Forte) just
after planting if there are problems with grasses such as
nut sedge and couch grass.
Dual Gold Must have rain
within 2 weeks of spray-
ing otherwise it becomes
completely ineective. If
too much is sprayed it can
kill beans or aect their
germination. The same
is true for Roundup. It is
thus important to be very
careful with herbicides if
intercropping and crop
rotation systems are to be
Roundup cannot be
sprayed on bare ground
or even if there is quite a
lot of dust or dry loose soil
in the eld. This inactivates
the Roundup.
Chemical fertilisers can restore soil fertility quickly because the nutrients are available to the
plants as soon as they dissolve in the soil. However they do not improve soil structure and
there are other disadvantages to using them.
CA leads to a reduction in fertiliser use, with improved soil health and improved yields. Working
with soil cover, crop rotation and cover crops is important to reach this goal.
There are many natural ways or products for improving soil health and fertility. Composting
and manuring are common examples. This is where manure (dung) from animals and compost
(humus) is added to the soil. Other examples include the use of liquid manures and brews,
organic or eco-friendly fertilisers, green manuring and cover crops, nitrogen xing trees, crop
rotation, mixed cropping and earthworm farming.
Adding organic matter results in many changes in the soil.
add organic
pore structure
reduced soilborne
diseases, parasitic
improved tilth
and water
humans and other
substances harmful
biological activity
(and diversity)
Improving soil health
We want to move from this ... ... to this
A comparison between chemical fertilisers and natural soil fertility methods
Soil Nutrients
All living things are composed of the basic elements of the earth. Plants consist mainly of
hydrogen, oxygen, carbon, nitrogen, phosphorus, potassium and smaller quantities of magne-
sium, sulphur and calcium as well as many other elements in very small amounts (these are
called trace elements).
The following table summarises the nutrients that plants need to grow well.
Chemical Fertilisers: DisadvantagesNatural soil fertility methods:
ÄChemical fertiliserfertilisers are quick-act-
ing, short- term plant boosters.
ÄThey can negatively impact on organic
matter and soil structure
ÄBenecial life in soil including earth-
worms are negatively impacted
ÄChemical fertiliserfertilisers alter vitamin
and protein content of certain crops
making them more vulnerable to diseas-
ÄGrowing plants often take up a lot of
nitrates which makes growth soft and
sappy and this is what pests love
ÄOver time essential elements can be
“locked up” and are therefore not availa-
ble to plants. This reduces the fertility of
the soil and plants can be more suscepti-
ble to disease and pest attack.
ÄThe activity of many soil organisms is
ÄThe soil tends to become acidic
ÄFertiliserFertilisers meet the basic nutri-
ent needs of soil NPK but what about all
the other elements?
ÄFertiliserFertilisers are inorganic. They
are manufactured in factories and this
is not sustainable and leads to climate
ÄFertiliserFertilisers are expensive to pro-
duce and buy
ÄChemical fertiliserfertilisers are easily
leached out. This can lead to pollution of
water sources
ÄWe are working with nature and natural
ÄNatural methods and products of im-
proving soil fertility work to address the
issue as a whole - by increasing a variety
of nutrient sources and levels, improving
soil structure, water holding capacity and
microbial activity (improving and encour-
aging life in the soil)
ÄWhen we use our own natural soil fertil-
ity methods, such as compost or cover
crop seeds, we are in charge, we don’t
have to rely on anybody
ÄIt is sustainable because we can keep
making compost/use natural methods
ÄNothing goes to waste and we recycle
ÄWe use what we have or can aord
ÄIt is cheaper to rely on and support nat-
ural processes than it is to buy external
inputs and agrochemicals.
ÄAlthough it takes time for organic matter
to decompose into humus and before
the nutrients are released, these nutri-
ents continueto improve soil fertility and
soil structure for a long time.
ÄNutrients are not as easily lost or leached
out and they are recycled in the soil
ÄCrops produced in healthy soils are nat-
urally healthy and show more resistance
to disease and pests
ÄAn increase in organic matter improves
inltration and soil water content and
reduces the likelihood of erosion
ElementCommon available
Needed in large amounts
O2 and H2O
and NH4
and HPO4
Atmosphere and soil pores
Water in soil pores
Needed in small amounts
FE+2 and FE+3
Cu+ and Cu+2
Plants need three main kinds of nutrients:
ÄNitrogen (N) – provides growth and green leaves;
ÄPhosphorus (P) – for healthy roots and fruit formation and pro-
vides hte plant with energy;
ÄPotassium (K) – for general health and healthy owers and fruit
and for providing plants with nice thick plant stems.
All three of these nutrients are found in healthy s oils and good com-
post or manure. You can also increase the amount of these nutrients
in the soil by mulching and crop rotations, especailly by mulching/ro-
tating with leguminous crops like beans, peas, pigeon peas and Aca-
cia (thorn tree leaves) or comfrey, using liquid manures and planting
cover crops or green manures.
Nitrogen (N)
Nitrogen is essential throughout the growing season. If
the maize plant runs out of N at a critical time, ears are
small and protein content is low. Kernels at the tip of
the ear do not ll.
How do you know if your soil needs more nitrogen?
You will know your plants need nitrogen when the leaves are turning yellowish, instead of a
strong bright green. There can
be general yellowing of the
older leaves and the whole
plant may be light green.
How can you add nitrogen to your soil?
This element is found in most manures (cattle, sheep, pig, goat, chicken and rabbit). There is
more nitrogen in chicken and goat manure. These must be dried before being used in the gar-
den. Otherwise they can be too strong and ‘burn’ the plants.
Nitrogen can also be added to soil through legumes. These are plants that form nodules or
little knots on their roots. These nodules ‘x’ nitrogen from the air, so that the plant can take
it up through its roots. There are microorganisms (bacteria) in the roots that help to ‘x’ the
nitrogen. After the roots of the plant die the nitrogen is released into the soil and can be used
by surrounding or following plants.
free nitrogen from air in the soil and
Examples of legumes that we often grow:
ÄBeans (including soybeans)
ÄAnd fodder crops such as vetch, lucerne, clover and forage peas.
There are less common crops and also many long living plants
and small trees that also x nitrogen. Some examples are chick-
peas, mung beans, lentils, pigeon peas, lab lab, velvet beans and
tree lucerne.
Some legumes are grown only as green manures, and are not
used for food. These include lab lab, velvet beans, lucerne, clover,
hairy vetch and lupins. These give a lot more nitrogen to the soil
than our food plants, because we atten them onto the soil sur-
face when they are still green. This is why we call them green ma-
nure cover crops. We can also plant our food crops in between
these legumes through intercropping.
In maize production shortages of phospphorus inter-
fere with pollination and kernel ll. Ears are small, often
twisted and with undeveloped kernels.
How do you know if your soil needs more
You will know your plants need more phosphorous when they do not grow fast, as they should.
The leaves may also start to show unusual red or pinkish colours, especially around the edg-
es. If your plants are small and will not grow, even when compost is added, then you almost
certainly have a severe
phosphorous deciency.
This can also be caused
by acidity in the soil.
How can you add phosphorous to your soil?
Many soils are poor in phosphorous. It is also a bit dicult to add phosphorous to the soil in an
organic way, as most of the sources of phosphorous are tricky to work with. They include urine,
bones, hair, feathers and blood. Usually we add these as ingredients to compost.
Natural rock phosphate can be added directly to the soil. This is also not easily available. An-
other good source of phosphorous is bone meal. You can usually buy this from an agricultural
supply store – but it is not cheap.
One other way of adding phosphorous is to
place bones in a re, for a few hours. You can
then grind them into a powder more easily.
This powder can be spread on your garden
beds or your compost heap.
The manure from animals grazing in areas where there is not much phosphorous will also have
little phosphorous. You may need to bring in phosphorous in the form of chemical fertiliser.
The usual source is called Superphosphate. Another chemical fertiliser known as MAP (Mo-
no-ammonium Phosphate) can also be used. It is a good practice to correct any soil P decien-
cies before starting with CA.
Potassium shortages in maize shows up in the ears
with poorly lled tips and loose, chay kernels.
How do you know if your soil needs more potassium?
You will know your plants need potassium when the plants become brittle and the leaf edges
become brown and dry. When fruit does not form properly, you should also suspect a lack of
potassium. Other signs can
be hard to distinguish. One of
these is a yellowing around
the veins of the leaves. This
could also be caused by dis-
eases – so it can be dicult to
How can you add potassium to your soil?
Good sources of potassium are chicken manure and fresh
woodash. Never use ash from coal, as this is very poison-
ous to the soil and plants. Another good source of potassi-
um is a plant known as comfrey. This plant has large hairy
leaves and grows in wet shady places. The leaves contain
a lot of potassium. These can be used to mulch your veg-
etable beds and also to make liquid feeds for your plants
(We will look at liquid feeds later in this section).
The other elements or minerals needed in smaller quanti-
ties, such as Magnesium, Zinc and Iron, are found in most
manure and in compost.
Other important nutrients:
Calcium (Ca): Promotes plant bre and strong plant tissue, promotes early root formation and
seedling growth, aids in the uptake of nutrients, balances pH
Magnesium (Mg): Essential for the formation of Chlorophyll and formation of sugars, a carrier
of phosphate and starches through the plant, promotes the formation of fats and oils, vital for
healthy growth.
Sulphur (S): Increases root development, helps maintain the dark green colour, stimulates seed
production, necessary for protein production, avor and odour in many fruits and vegetables.
Micro or trace elements (nutrients needed in smaller quantities)
Iron (Fe): Is an oxygen carrier, enhances chlorophyll formation, metabolizes RNA, enhances
green color of produce
Boron (Bo): Promotes early root formation and growth, improves health and sturdiness, in-
creases yield and improves quality of fruits and vegetables. Improves the performance and
availability of both calcium and silica.
Zinc (Zn): Essential for enzymatic reactions in cells and promotes plant growth.
From: Useful Plants for Land Design, Pelum
Copper (Cu): Is needed for Chlorophyll production, catalyzes several plant reactions and neces-
sary for making protein.
Manganese (Mn): Activates many metabolic reactions, increases absorption of calcium, magne-
sium and phosphorus, speeds germination and plant maturity.
Molybdenum (Mo): Enhances absorption of nitrogen by plants
Chlorine (Cl): Involved in photosynthesis and chlorophyll production, stimulates enzyme activi-
ty, helps control water loss and moisture stress.
Cobalt (C): Is needed in nodules of legumes for nitrogen xing bacteria
Sodium (Na): Helps in water regulation and photosynthesis
These nutrients are important to plants for health and survival. They are equally important
to animals and human health. This is because we get our nutrients from plants who take up
essential nutrients from the soil. If our soil is healthy our plants benet by being healthy and we
in turn benet from the variety of nutrients available.
Soil acidity
What is soil acidity?
Soil acidity can inuence plant growth and limit crop yield. Minerals or nutrients needed by
plants to grow are dissolved in the water inside the soil. This is a bit like salt or sugar dissolved
in a glass of water.
Soil acidity is when the soil is “sour”.
It is a bit like a glass of water that has
vinegar dissolved in it. In places where
it rains a lot, some of the minerals can
be washed out of the soil. The soil then
becomes acidic. The use of chemical
fertiliserfertilisers over a long period of
time can also make the soil acidic.
If there is too much acid in the soil,
some minerals or plant food will dis-
solve too quickly and the plants cannot
use them. Other minerals will not dis-
solve at all, so again, the plants cannot
use them. Phosphorus is one of the
minerals that cannot be used by plants
when the soil is acidic – even if it is in
the soil.
What causes acidity?
Acidic parent rock material, high rainfall and leaching of elements like calcium (Ca), magnesium
(Mg), and phosphorous (K), decay of organic matter leading to release of organic acids into the
soil, harvesting high yields (therefore removing plenty of Ca, Mg and K from the soil) and wide-
spread use of nitrogen (N) fertiliserfertilisers cause soil acidity.
How do you know if your soil is acidic?
You will know your soil is acidic if you provide compost or manure and water for your plants,
but they do not grow. The plants remain small and stunted. This is a common problem.
Maize plants growing in acidic soil will have stunted shoots and leaves that are stubby and die
back at tips. The leaf color is dull green with leaves and stems developing purple tints similar to
phosphorus deciency. Roots are short and stubby and lack ber.
pH is a measure of the soil’s acidity or alkalinity. In water, it normally ranges from -1 to 14, with
7 being neutral. A pH below 7 is acidic and above 7 is alkaline. Soil pH is considered an impor-
tant variable in soils as it controls many chemical processes that take place. It specically aects
plant nutrient availability by controlling the chemical forms of the nutrient. The optimum pH
range for most plants is between 5.5 and 7.0. Soils below a pH (KCL) of 4,5 are considered to be
very acidic/sour.
The primary cause of acid soil infertility is Aluminium toxicity and unavailability of existing Phos-
phorus (P) as well as Magnesium (Mg) and Molybdenum (Mo).
Acid saturation measures the total amount of exchangeable acidity or ion (cations). This diers
for sandy and clay soils and thus a measure of acid saturation is given which indicates this for
each type of soil. For growing maize acid saturation should not be higher than 20%
How will you solve the problem of acidity?
The only practical way of dealing with soil acidity is to add lime to the soil. The ideal agricultural
lime is produced from limestone and/or dolomite rocks and consist primarily of calcium (Ca)
and magnesium (Mg) carbonates. Lime can be bought and is a white powder, or grey granules.
It can either be dug into your soil, at least as deep as the roots of the crop you are growing or
be spread across the surface, or placed on the surface of the soil to be incorporated over time
through natural processes.
Without the benet of a soil sample analysis result a general rule of adding 1-2 tons/ha of lime
every 2-3 years can be used.
Usually lime is added 2 or 3 months before planting, as it is slow acting in the soil. If you add
Lime at the same time as you are planting your crop, you will only see the main eect of the
Lime in the next season. It is a good practice to correct soil acidity through the addition of lime
before starting with CA.
Inorganic fertilisers
These are chemcials that you buy that contain the main plant nutrients or food in specic
The capital letters in brackets (N, P, and K) are called the chemical symbols. If you buy com-
pound fertiliserfertilisers, they may use these letters instead of writing out the name in full.
An example is N:P:K or 3:2:1 which means the fertiliser contains 3 parts N to 2 parts P and
1 part K.
Compound fertiliser iso soil nutrient treatments
There are many dierent fertilisers that can be bought that supply dierent amounts of the
main nutrients. To know how much of each element you have to add, a soil sample analysis is
done by a laboratory. These results will generally tell you how much of each nutrient is re-
It is also possible to use manure in stead of fertiliser and to use manure and fertiliser mixtures.
Below is a table of common fertilisers and manures and the quantities of nutrients they pro-
3:2:1 (22)
It is also possible to
buy the fertilisers
that supply a single
nutrient at a time
such as LAN, Supers
and KCL.
Fertiliser NameChemical composition
%N %P%K
LAN (limestone ammonium nitrate) (28)28--
Urea (46) *more concentrated than LAN but more acidifying46 --
MAP (Monoammonium phosphate (33)1122-
Single supers (10,5)-10,5
KCL (Potassium Chloride) (50)--50
Cattle, horse0,5 0,3 0,5
Improved Cattle 2,0 1,5 2,2
Goat0,9 0,5 0,8
Improved Poultry 42,71,4
2:3:4(30)+0,5% Zn6,71013,3
3:2:1 (25) + 0,5% Zn12,58,34,2
NOTE 1: You will see that the singler fertilisers add much higher concentrations of the nutrients than the fertiliser
NOTE 2:Animalmanuresdieraccordingtowherehteanimalscomefromandwhattheyhavebeeneating.If
NOTE 3:Improvedmanures,thosethathavebeencomposted,providemuchhighernutrientquantities.
Here is an example of a fertiliser reommendation given for growing maize, for a
soil sample around the Bergville area in KZN.
The following are fertiliser options (given in bags/ha) using DAP, MAP, Single Supers,
2:3:4 (38), KCl, LAN and urea for a specic soil sample.
Soilsampleyieldtarget(t/ha)4.0 – the amount of fertiliser added will increase the yield up to
a point. So it is possible to decide on your target yield. There are a number of dierent combi-
nations of fertilisers possible to give the correct amounts:
Ä4.0 bags/ha DAP; 1.0 bags/ha LAN or 0.6 bags/ha urea.
Ä3.6 bags/ha MAP; 2.1 bags/ha LAN or 1.3 bags/ha urea.
Ä7.6 bags/ha Single Supers (10.5%P); 3.6 bags/ha LAN or 2.2 bags/ha urea.
Ä6.3 bags/ha 2:3:4(38); 1.7 bags/ha LAN or 1.0 bags/ha urea. The 2:3:4 would supply
more than sucient K.
Ä4.0 bags/ha DAP; 7.4 bags/ha LAN or 4.5 bags/ha urea.
Ä3.6 bags/ha MAP; 8.6 bags/ha LAN or 5.2 bags/ha urea.
Ä7.6 bags/ha Single Supers (10.5%P); 10.0 bags/ha LAN or 6.1 bags/ha urea.
Ä6.3 bags/ha 2:3:4(38); 8.1 bags/ha LAN or 4.9 bags/ha urea. The 2:3:4 would supply
more than sucient K.
Ä4.0 bags/ha DAP; 10.3 bags/ha LAN or 6.3 bags/ha urea.
Ä3.6 bags/ha MAP; 11.4 bags/ha LAN or 7.0 bags/ha urea.
Ä7.6 bags/ha Single Supers (10.5%P); 12.9 bags/ha LAN or 7.8 bags/ha urea.
Ä6.3 bags/ha 2:3:4(38); 11.0 bags/ha LAN or 6.7 bags/ha urea. The 2:3:4 would supply
more than sucient K.
From these recommendations it can be seen that to increase the target yield, more LAN
is added and most likely as a top dressing when the maize is knee high. It is important to
split the applications of N as it can be washed away and moves down into the soil prole
where it may not be available for plants.
Micro dosing
Micro dosing is a method of adding small quantities of fertiliser directly adjacent or next to
plants where they can use it, rather than placing the fertiliser in bands or spreading it across
the whole eld. In this way much less fertiliser is used. This method is practised with CA. It is
also recommended that fertiliser, manure combinations are used and that as little fertiliser as
possible is used.
Below is a table that give general recommendations for use of fertiliser and manure when
planting maize in a CA system.
Fertiliser and Manure Quantities
Unless a soil sample specically mentions the need for potassium (K), it is assumed that the
higher clay soils (especially in KZN) as a rule do not need extra additions of potassium.The grey
blocks represent a general recommendation for the midlands in KZN.
NAMEElementAmount/haAmount/m2 Measuring
28% N100kg/ha =
355kg LAN
18 g /meter of row
9 g/planting basin
2 match boxes
1 matchbox
½ match box
28%N40kg/ha ~140kg
5g/meter row
2.5g/planting basin
2 cooldrink bottle tops
1 cooldrink bottle top/
1 teaspoon
½ cooldrink bottle top/
½ teaspoon
Supers 10.5% P40kg/ha =
380kg supers
20g/meter row
10 g/planting basin
2 match boxes
1 match box
½ matchbox
MAP (33)
N and P)
11% N,
22% P
55 kg/ha P,
30kg/ha N =
250kg MAP
18g/ m2
8,3g/meter row
4,2g/planting basin
1 match box/ 1 table-
½ match box
1 cooldrink bottle top/
1 teaspoon
KCL 50% K20kg/ha = 40 kg
2 g/meter of row
1g/planting basin
1 cooldrink bottle top
½ bottle top (½ tea-
¼ bottle top (½ tea-
Lime 1ton/ha1kg/m2
500g/meter row
250g/planting basin
1 large jam tin
½ large jam tin (or 1
normal food tin)
¼ large jam tin (½ food
5kg/t N
2kg/t P
3kg/t K
10 tons/ha10kg/m2
5kg/ meter row
4 heaped spade fulls
2 spade fulls
1 spade full/ 4 large
jam tins
1tsp/cooldrinkbottletop~2.5-5g 1matchbox/tablespoon~15-25g1largetin~400-900g
With green manure/cover crops we use plants to improve and protect the soil. Green manures
and cover crops have thus far been understood to be crops grown by themselves, with the
primary aim of increasing soil fertility and which are then ploughed back into the soil when they
are in the owering stage and still green.
In CA and as smallholders, we use cover crops somewhat dierently:
Maize and cowpea intercropRelay cropping of winter cover
crops: saia oats, fodder radish
and vetch
Collecting seed of winter cover
Firstly, rather than always being planted alone, cover crops are usually planted together with
the main food crops and at about the same time (intercropped), or they are planted among the
main food crops just before these crops are harvested (relay intercropping). Now farmers can
improve their soil without dedicating extra land to growing these crops
Secondly, cover crops are cut or rolled down after their seed is harvested, so that we can use
the seed as food for humans and animals and replant them
Thirdly, the cover crops are cut or rolled down and left on top of the soil as we do not disturb
the soil through ploughing – the organic matter on the soil surface can protect the soil from
sun, wind and rain and provide extra soil fertility.
Fourthly, we plant cover crops to control weeds, pests and diseases. Cover crops compete with
weeds and very eectively prevent or suppress them from growing. Cover crops ‘push’ or ‘pull’
pests and diseases out of the elds and/or away from food crops, since they are either liked or
disliked by them.
Cover crops
Advantages of planting cover crops (CCs)
1. Increased organic matter and soil nutrients: CCs are capable of adding as much as 50
metric tons/hectare (MT/ha) or more of organic matter (green weight) to the soil each year.
This organic matter has various positive eects on the soil, such as recycling nutrients back
into the soil, pumping nutrients up to the soil surface, and improving the soil’s water-holding
capacity. It can also increase the total amount of nutrients in the soil, improve its nutrient
balance, increase the number of macro and microorganisms (very small animals in the soil,
many of which also help a farmer’s crops grow better), improve the acidity of soil (i.e.: buer
soil pH) and sequester carbon.
Organic matter makes soil nutrients, including those supplied by chemical fertilizers, more
accessible to crops. In the case of phosphorus, this is particularly important: in acidic soils,
phosphorus may become four to ve times more available to plants when surrounded by
organic matter.
2. Nitrogenxation: Legumes (plants that produce their seeds inside pods) are able to x
nitrogen (N) from the atmosphere into a plant-usable form that accumulates in plant tissues.
Legumes can thereby add large quantities of nitrogen to farmers’ soils. Most of the widely
used legume CCs are capable of producing more than 50 kg N/ha; some a lot more.
3. Weed and pest control: CCs can also be an important factor in reducing the cost and the
labour required for controlling weeds. Herbicide use is either reduced or eliminated, since
many CC species are able to smother weeds. Some species of CC can be used in place of
other chemicals. For example, mucuna (velvet bean) and lablab beans kill nematodes, while
sunnhemp (Crotalaria ochroleuca) can be used to control pests that eat stored grain. Bras-
sicas (plants in the cabbage family) have an allelopathic eect that inhibits the germination
of small seeded weeds. Rye, wheat and hairy vetch also produce compounds that inhibit
4. Soil cover and erosion control: The soil cover provided by many CCs can be very important
for soil conservation. The soil cover, or mulch, that is provided by a CC also greatly improves
drought resistance. The residues add organic matter to the soil, which increases inltration
of water into the soil and increases the water-holding capacity of the soil, while run-o and
erosion is reduced substantially. Cover crops protect soil aggregates from the impact of rain
drops by reducing soil aggregate breakdown.
Left: Runo in a eld planted to maize only has washed away some of the younger and germinating plants
Right: On the same eld intercropping with a cc has reduced the runo a lot and crops are doing well
5. Mycorrhizal Fungi: Cover crops increase mycorrhizal fungus activity promoting a symbiotic
relationship with the plants’ roots for water and nutrient uptake. Plants provide the poly-
saccharides and the mycorrhizal fungus provide the protein to form a glycoprotein called
glomalin which promotes soil aggregate stability (more macro-aggregates) and improved soil
structure. Mycorrhizal fungus
grows better in undisturbed
soils. No-till and actively grow-
ing roots promote this reaction
to occur. The majority of soil
microbes are located next
to growing roots with 10,000
times more microbes located
in the rhizosphere next to the
root than in bare soil.
The soil microbial biomass and
enzymatic activity increases
with cover crop usage. Cover
crops increase SOM, macropo-
rosity, soil permeability, mean
aggregate size, and aggregate
stability (macro aggregates vs.
6. Additionalbenets:
ÄCCs can provide food for humans and fodder for animals, including cattle and poultry.
ÄCCs can provide economic benet through sale of fodder, hay and seed
ÄCCs can reduce pest attack and problems on staple crops including nematodes in growing
crops and various pests in stored grain. CCs can be used as a trap crop for insects if the
cover crop is killed before planting maize. Some green cover crops attract army worm, cut-
worms and slugs so the cover crop needs to be killed 3 to 4 weeks before planting maize.
ÄLetting cover crops grow and mature (ower) may allow populations of benecial insects to
ÄCCs can reduce incidence of diseases in crops, notably root rots and other fungal diseases.
ÄCCs can alleviate soil compaction through improved root sysems and soil structure.
ÄCCs increase the solar energy harvest (through photosynthesis) to increase carbon in the
Livestock grazing on a fodder rye and clover mixture of cover crops (from: S Hodgson, 2014)
Roots, fungal hyphae and their secretions stabilize soil aggregates
and promote good soil structure, thus preventing compaction and
increasing soil water holding capacity and nutrient cycling
ÄCCs provide food for macro- and micro-organisms and other wildlife.
ÄCCs increase organic carbon, cation exchange capacity, aggregate stability and water inltra-
Disadvantages of planting CCs
1. Opportunity cost of land: Farmers normally will not plant something that only improves
their soil if the land could instead be planted with either food crops or cash crops. Unless the
CCs also produce food, the land used to grow CCs must have no other valuable use
2. The slow results: Soil improvement is a long-term process that may not be immediately
noticeable to the farmer. Usually, concrete, visible results are not apparent until well into
the second cropping cycle. This slow appearance of results – improved soils – that are often
dicult for people to believe, further complicates the adoption of CCs.
3. Dry season problems: Often CCs must produce their organic matter at the end of the wet
season, or must continue to grow during the dry season. Grazing animals, wild animals,
termites, agricultural burning, bush/veld res or several other problems may destroy organic
matter or growing plants before the farmer can use them the following rainy season.
4. Timing (also called “synchronization”): The nutrients provided by the CCs, especially nitro-
gen, must be available to crops when they need them in order to raise productivity. CCs will
boost farmers’ productivity only if the nutrients are available to the crops at the right time. In
many systems, the correct timing is either impossible or very dicult to achieve. Therefore,
the eciency of the systems is reduced.
Nutrient cycling and release
with cover crops
Generally cover crops consist of mixtures of grasses
and or grains and legumes to balance the need for
inclusion of both carbon (C) and nitrogen (N) to build
the soil. Both C and N are needed to form soil or-
ganic matter. Grass cover crops may contribute N as
scavengers or legumes may x additional N. Grasses
contribute more carbon than legumes. The carbon to
nitrogen ratio (C:N) determines how organic matter is
decomposed, at which rate and which nutrients are
released or held in more stable forms. At C:N ratios
of less than 20, N is released. The average C:N ratio in
the soil is around 10-12:1 indicating that N is available.
Nitrogen uptake depends on how much nitrogen is in
the soil, the climate (temperature and water), cover
crop species, seeding rate, planting and die back or
killing date. Winter grass cover crops (such as saia oats
and annual ryegrass) accumulate soil N in autumn and
winter due to fast root growth. After the boot stage
(when the stems start to thicken and lengthen), there
is not much additional nitrogen uptake with grasses.
Legumes accumulate nitrogen longer into the spring.
Grasses and or brassica species absorb and recycle
nitrogen if excess N occurs from manure or fertilizer.
Legumes are used to supplement N for the next crop
if more N is needed for fertilization.
The release of N depends on
cover crop species, growth stage,
management, and climate. For
An early spring kill of grasses
promotes a lower C:N ratio and a
faster release of N.
Legumes tend to have a lower
C:N ratio but if either grasses or
legumes are allowed to reach full
maturity, N release is delayed.
Slower N release occurs more in
dry weather than in wet years due
to decreased microbial activity
needed to decompose residues
and release N
N uptake of cover crops varies
from 57 to 296 kg N/ha. If 50%
of N is recycled, cover crops may
supply 25 to 132 kg N/ha to the
next crop
Late planted cover crops may not
have as much vegetative growth
but may impact soil and water
quality through reduced soil
Types of cover crops
Mostly mixtures of grasses, legumes and bras-
sicas (cabbage family) are used. The general
rule is to plant as many dierent types of cover
crops together as possible. The most ecient
organic matter building process is through a
diverse range of cover crops that help to main-
tain a diverse microbial community.
When ve or more species or types are planted
together, such as grasses, cereals, brassicas,
legumes and chenopods (a family of plants
that includes spinach, beetroot, amaranthus
and lamb’s quarters or chenopodium), syner-
gistic eects start to be noticed. More phenolic
compounds are produced in the plants and
microorganisms. These compounds have a
role to play in the xation of nitrogen and also
in building resistance to insect and disease
We can choose the combination of cover crop
mixes depending on the season, the rainfall
and the requirements of the soil in our situ-
ation. For smallholder farmers we would be
looking mostly for mixes with good grazing and
food potential.
Examples of commonly used cover crops
Annual cover crops that are used as rotations with summer and winter grain crops are the most
common. Cover crops need to be good fodder for livestock as well as having soil building and
soil health improvement properties. In the South African conditions they need to be tolerant to
bad quality soils that are often acidic or sandy and to heat and drought stress.
Common cover crop options for legumes:
Warm seasonCool season
Dolichos (Lablab purpurea)
Sunnhemp (Crotalaria juncea)
Cowpea (Vigna unguiculata)
Lucerne (Medicago sativa)
Velvet beans (Mucuna pruriens)
Soybean (Glycine max)
Mung bean
Hairy vetch (Vicia villosa)
Burmedic (Medicago polymorpha)
Red clover (Trifolium pratense)
Forage pea/eld pea (Pisum sativum)
Top: Amaranthus species are good cover crops and
also provide food as indigenous greens
Below: Chenopodium or lambs quarters similarly is a
highly nutritious vegetable
Dolichos beans (Lablab purpureus)
Lablab is remarkably adaptable to wide areas
under diverse climatic conditions and soil
types with pH varying from 4.4 to 7.8. Being a
legume, it can x atmospheric nitrogen to the
extent of around 170 kg/ha besides leaving
enough crop residues to enrich the soils with
organic matter. It is a drought tolerant crop
and grows well in dry lands with limited rain-
fall. The crop prefers relatively cool seasons
(temperature ranging from 14-28°C) with the
sowing done in July-August. It is an extremely
good high protein animal fodder for the dry
season and is highly preferred by cattle. It
seeds throughout the dry season and will not
provide seed under heavy grazing conditions.
(Truter et al 2015)
Right: Lablab grows prolically and seeds late in the
season going into winter. It provides full ground cover
while maize is dying back
Sunnhemp (Crotalaria juncea)
This is a tropical legume that has huge poten-
tial as a cover crop. It is planted in the warm
season and is an annual that produces large
quantities of biomass. It is a good fodder for
livestock and grows in low fertility sandy soils.
It has a suppression eect on plant parasitic
nematodes and xes around 120kg/ha of
Left: Sunnhemp grows tall and straight and seeds
quickly producing high biomass and protein rich
Lucerne/Alfalfa (Medicago sativa)
This is a perennial owering plant in the pea
family and is grown as an important livestock
fodder crop. It is also considered a good
crop for promoting the presence of bene-
cial insects such as predatory and parasitic
wasps. It is hardy and drought tolerant. This
deep rooted crop breaks up hard soils and
recycles nutrients bringing trace elements to
the soil surface. It can be cut and hay can be
produced, or grazed directly. It is planted in
spring. It xes between 180-250kg/ha of nitro-
gen. Above: Lucerne can be cut and fed to livestock 2-3
times per season. It produces a very high value hay
Bur Medic (Medicago polymorpha) is a leg-
ume that is closely related to alfalfa/ lucerne.
They x around 120kgN/ha. They are true
annuals owering, setting seed and dying with-
in one growing season (60 to 100 days). The
germinate and grow quickly and can tolerate
a wide range of soil pH. They can be used for
Right: Medics are used very successfully in dryland
conditions with poor quality soils
Hairy Vetch (Vicia villosa)
These legumes are planted in autumn and al-
though a bit slow to establish as drought and
cold tolerant once growing. They can grow
in a wide range of dierent soil types and
dierent pH and also do well in sandy soil.
They show good N xation at around 140kg/
ha of N.
Left: Hairy vetch is one of the most rewarding cover
crops. The small leaves and high biomass means fast
decomposition and a signicant increase in organic
matter in the soil
Red Clover (Trifolium pratense)
This is sown as a cool season cover crop and
is shade tolerant if sown into a maize crop
towards the end of the season. It xes around
140kg/ha of Nitrogen and can be grazed in
Right: Clovers do well on highly clay and acidic soils
where other cover crops may struggle. They are well
adapted to cool wet conditions
Forage pea (Pisum sativum)
These are winter legumes and good fodder
crops for livestock. They are not very drought
tolerant and require non acidic soil for opti-
mum growth.
Left: The forage peas are a little slow to germinate and
cannot tolerate very hard soils and dry conditions.
Grasses, cereals and brassicas
Common cover crop options for grasses, cereals and brassicas include the following:
Warm seasonCool season
Babala/ pearl millet (Pennisitum glaucum)
Forage sorghum (Sorghum bicolor)
Black/saia oats (Avena strigosa)
Fodder rye (Secale cereale)
Fodder radish (Raphanus Sativus Olieformis)
Other bassicas including: kale, rape, turnips
and mustard
White oats
Stooling rye
Cereal/ fodder rye (Secale cereale)
This is sown in autumn and forms dense
stands and a large root mass. It is quite
drought and cold tolerant and good for prob-
lem soils such as rocky or sandy soils.
Right: The grain can also be kept as food for livestock
and humans and is comparatively high in protein
Black oats (Avena strigosa)
This is a good cool season cover crop and is a
valuable fodder crop for livestock, with good
nutrition quality and high protein content. It
is quite hardy, can tolerate low pH soils and
improves soil aggregation and soil structure.
It also mobilises C alcium (Ca) in the soil.
Left: Black oats forms one of the standard cover crop
mixes as it has a strongly boosting eect on soil health
and soil microbial life
Babala/pearl millet (Pennisitum glaucum)
This is a quick growing summer annual used
for grazing and silage. It has a well developed
root system and good drought tolerance. It
can tolerate low soil fertility, and high tem-
perature. It performs well in soils with high
salinity or low pH. Because of its tolerance to
dicult growing conditions, it can be grown in
areas where other cereal crops, such as maize
or wheat, would not survive. In many parts of
the world including Africa and India it is staple
food eaten as a porridge or fermented into a
local beer. Flatbreads, cakes and biscuits are
also common. www.great-secret-of-lifecom
Above: Pearl millet is a good food for both livestock
and humans
Forage sorghum (Sorghum bicolour)
This sorghum type grows very tall and pro-
duces a large amount of vegetative growth.
It is drought and heat tolerant and produces
good animal fodder. It is also known as sweet
Right: Forage sorghum is a very good cattle fodder and
also known as sweet reed in more local cultures, it is
eaten like sugarcane
Fodder radish (Raphanus Sativus Olieformis)
It is a fast growing cool season cover crop
which is immune to many brassica diseases,
such as clubroot. It has a weed suppression
eect and is a good grazing crop for livestock.
It is cold tolerant and has positive eects on
soil health and soil structure. It grows large
very quickly and has a large nitrogen uptake
of around 20kg/ha. It has a positive eect on
acidic soils and xes Aluminium (Al).
Left: Fodder radish and oats mixture and the large
root that cracks open and aerates soil as well as being
a particularly sought after fodder for cattle
Seed inoculation
Inoculation may be dened as the process of adding
eective bacteria to the host plant seed before plant-
ing. The purpose of inoculation is to make sure that
there is enough of the correct type of bacteria that
multiply in the roots of a legume plant forming nod-
ules where these bacteria x atmospheric nitrogen
for the nutrition of the plant. These inoculants can be
bought and added to legume seeds prior to planting
Inoculants are specic to each type of legume.
More recently inoculants containing benecial fun-
gi such as mycorrhizae have also been developed.
These assist in general soil health and plant growth.
Hoorman J.J. 2015. Using Cover Crops to Improve Soil and Water Quality. Cover Crops & Water
Quality, Extension Educator Ohio State University Extension, Lima, Ohio
Bunch, R. 2012. Restoring the soil. A Guide for Using Green Manure/Cover Crops to Improve the Food
Security of Smallholder Farmers. Canadian Foodgrains Bank, Winnipeg, Canada.
Hodgson, S. 2015. Cover crop mixes. Cover Crop Solutions. Box 195 Umlaas Road 3730 E-mail:
Sait, G. 2015. It’s cocktail time. The amazing potential of engineered biodiversity. In Nutrition Mat-
Truter, W., Dannhauser, C., Smith, H. and Trytsman, G. 2015. Conservation Agriculture - Inte-
grated crop and pasture-based livestock production systems. A series of articles on various
crops. SA Grain Magazine,
The general rule is to mix cereals/ grasses, legumes
and brassicas into the mixture. Any combination of
these can wok well- depending on the local conditions
and preferences. Remember to try and use as many
dierent types and species as possible.
A good mixture is the following:
Dolichos (Lab-Lab beans)
Fodder sorghum and Sunnhemp.
Right: A trial plot with the summer mix of cover crops
(from: H Smith, 2014)
Cool season cover crop
Various combinations of black
oats fodder rye, vetch fodder
radish and fodder peas are
Right: A plot with fodder pea,
oats and rye grass;
Far Right: A mix of hairy vetch,
fodder peas and fodder rye.
(From S Hodgson SACCS, 2014)