SOIL FERTILITY MANAGEMENT
AND OTHER KNOWLEDGE FOR
IMPROVING CROP YIELDS
WITH A FOCUS ON NITROGEN MANAGEMENT
ILLUSTRATOR: BUNAYA MBEWE
TRANSLATOR: HASTINGS SIMWABA
EDITOR: ELLIOT W. LUNGU
AUTHORS: BEN and STACEY WATERMAN
CONTRIBUTIONS ALSO FROM U.S. PEACE CORPS, MALAWI
ENVIRONMENTAL SECTOR
PO BOX 208, LILONGWE, MALAWI
And
MUTUNGUJA COMMUNITY LIBRARY
P/A NCHENACHENA
P/O RUMPHI
And
Peter Jensen
Permaculture Specialist
Peace Corps Tanzania
i
TABLE OF CONTENTS
PART ONE
I.
INTRODUCTION
1
II. A WORD ABOUT NITROGEN
3
III. SOIL, WHAT IS IT?
4
IV. WHAT DO PLANTS WANT?
5
V. FERTILIZER, WHAT IS IT?
6
VI. SYNTHETIC FERTILIZER, WHAT IS IT?
7
PART TWO
VII.
LEGUMES
11
VIII. URINE
15
IV.
ANIMAL MANURES
17
X.
COMPOST MANURE
18
PART THREE
XI.
AVAILABILITY OF NUTRIENTS, WET AREAS
22
XII.
AVAILABILITY OF NUTRIENTS, DRY AREAS
24
XIII.
TO BURN OR NOT TO BURN, THAT IS THE QUESTION
29
XiV.
XV.
BIO-INTENSIVE MINI FARMING
32
CONCLUSIONS
34
ii
INTRODUCTION: FERTILIZER AND OTHER WAYS TO INCREASE
YIELDS
Everyone is familiar with the benefits of synthetic fertilizer. Just take a walk through
crop fields and you very easily see that those who have used fertilizer have big, beautiful
green plants, while those who have not have yellow, smaller, or unhealthy plants. Those
who have used fertilizer will be eating plenty of maize, but those who have not might be
hungry. Provided you have it, fertilizer is easy to use, and anyone can learn how to apply it
properly.
Fertilizer has been almost like a miracle that can significantly increase food
security and alleviate hunger.
Concerning miracles, there is a Tumbuka proverb that goes like this: “Kakwiza Kekha
Kana Msiku”, in other words, its only miracles that come on their own, and if you want
anything good, you have to work for it. Such is the case with growing food. It takes hard
work, and every farmer knows that.
Fertilizer may be a miracle, but there were surely
farmers before fertilizer came into being.
They grew good food without buying sacs of
fertilizer, and did not starve, for if they did, we would not be here today. They did other
things to add nutrients to their gardens or fields. This book is about the many things that
farmers can do to harvest good crops. Farming is not just finding fertilizer and adding it to
fields. There are many other things that farmers can do. They might be hard to do, they
might take planning ahead, and they might take a long time, but remember, its only miracles
that come on their own!
Only Miracles Come On Their Own
1
This book is therefore not a book about fertilizer, but about fertility. If anything, after
reading what follows, you might have a different definition of the word “feteleza”. When you
think of “feteleza” you might think of planting legumes, preventing soil erosion or using
manure. These management practices will all be like “feteleza”, helping your crops in the
same way fertilizer from a sac does. Then, you can put your new knowledge to practice in
the field. You can:
1.) Use the same amount of fertilizer, but now grow more food, or
2.) Grow the same amount of food, but maybe use less fertilizer, saving yourself money in
the process.
There is another Tumbuka proverb that is very appropriate here:
“Kumuwuzganga Ntha Ndi Fwiti, Fwiti Ndi Tiringanenge,” meaning to warn
another is not “witchcraft”, but "witchcraft" is just going with the flow. In other
words, while it might not be easy, you should warn your friends so they can
prevent problems. Staying silent is doing them a disservice. With that said, this
book is also a warning. You will read all about how synthetic fertilizer is made
and why it is so expensive.
expensive in the future.
You will also be warned that it may be more
The lesson is this:
If people practice other ways of
improving their soils, future hardship can be avoided.
2
A Word About Nitrogen
The Strength of a Chain Depends on its Weakest Link
The following pages are focused on management practices aimed at improving soil
fertility, with a focus on nitrogen. Nitrogen is perhaps one of the most important nutrients
to manage.
It is responsible for making leaves green through the manufacturing of
chlorophyll. This enables plants to photosynthesize and grow rapidly. Nitrogen is a vital
component in plant proteins, which crops use to grow big and strong.
Nitrogen
is
also
important to consider because out of all the essential nutrients it is often the scarcest in soils
due to neglect by farmers or due to its volatile nature. When nitrogen is limited, all other
plant nutrients can’t be utilized because crop growth is stunted. Nitrogen is also a main food
for microorganisms that make more nutrients available in the future; with limited nitrogen
their activity slows dramatically. Limited nitrogen is almost like a hole in a pot that prevents
you from ever being able to fill it all the way, or similar to one weak link in a chain that
causes the whole chain to break when it’s needed most.
3
What is soil? How does it work?
Topsoil Is A Valuable Natural Resource
In general, soils are made up of four main components:
1. Mineral material (rocks particles of sand, silt and clay),
2. Air that fills the spaces between the solids,
4.
3. Water in the soil, and
Organic matter (humus), made up of plant and animal material at various stages of
decomposition. Different soils have different proportions of each of these components.
Plants generally grow best in soils that have a lot of organic matter. This is because
organic matter leaves more spaces for air and water to be stored in the soil and makes it
easier for plant roots to move through the soil. Organic matter is food for microorganisms,
so soil with more organic matter has more microorganisms. As they decompose organic
matter, many plant nutrients are made available to plant roots in the soil.
Microorganisms
also help make available other plant nutrients such as P (phosphorus), K (potassium), and
Mg (magnesium) by weathering rock minerals in the soil.
4
Bacteria From Organic Matter Help Make Nutrients Available From Weathering
On the other hand, a soil with very little organic matter tends to be heavier, with
fewer spaces for air and water to be stored in the soil. As well, a soil with little organic
matter provides few nutrients for plants, thus creating the need for expensive synthetic
fertilizers produced in a factory. The less organic matter in your soil, the more synthetic
fertilizer you will need to buy to provide enough nutrients for your crops.
What Do Plants Want?
Plants are living things and they have the same needs as all living things. They need
food, water and a nice place to live. For a plant, a nice place to live means a place that’s not
too hot, but not too cold, that provides enough water to drink but not too much water and
enough nutrients to grow and be healthy. Isn’t that what we all want? So is it the farmer’s
job to provide each and every plant with these things? Actually, the soil will provide all of
these things for the plant for free as long as it is a healthy soil with lots of organic matter.
So really, the farmer should concentrate on taking care of the soil. Let the soil take care of
all of those plants! Think about it – does a forest need synthetic fertilizer to grow thousands
of huge trees? A forest recycles its own nutrients through the soil. Those nutrients are used
by the trees for growth. So we can see that the soil can provide all of the things that a plant
needs. It is only when our soil fails, or we fail our soil that we need to add fertilizer from
synthetic sources. Fertilizer came from the soil long before fertilizer ever came from a sac.
5
Fertilizer, What Is It?
If you ask most people what fertilizer is, they will answer like this: “Fertilizer is the
thing which you buy in sacs at the store. ” Now assume a maize plant could talk. It would
answer like this: “Fertilizer is the things which I find in the soil.” The farmer and his maize
plant seem to be saying two different things. Why the contradiction?
Both the farmer and his maize plant are correct. Fertilizer is made by man in factories
and sold in stores. It is also found everywhere in nature, including soils. The nutrients
found in nature are in fact the same exact nutrients found in fertilizer sacs. To the maize
plant, it doesn’t matter where the nutrients come from; as long as they are present in soils
around the roots, so the maize plant can take them up, grow, and bear big cobs. It is
therefore the farmer's duty to know where nutrients are found, other than inside fertilizer
sacs. He must also know how those nutrients will act or move through soil, in order to know
when and where they will be available for plant uptake.
To A Maize Plant, All Fertilizer Or Nutrients Are Found In Soil
So where can all these nutrients be found? Examples will be given throughout this
book. The main point is that the various nutrients essential for plant growth are the same
regardless of their source.
A bag of “23-21-0 + 4S” has 23% nitrogen (NH4+), 21%,
6
phosphorus (PO4--), 0 % potassium (K+) and 4% sulfur (SO4--), but, that same nitrogen is
found in urine. That same phosphorus is found in ash. That same potassium is found in
banana peels. That same sulfur is found in decomposing crop residues. The only difference
is in the amount or concentration of the nutrient found in one place. Nitrogen in human
urine, for example, is about 15%, while it is 45% in a bag of urea fertilizer. All food is
grown with fertilizer because all plants use nutrients. A man or woman can take powdered
nutrients out of a sac and put it on the soil, or the nutrients can get into the soil other ways.
The maize plant knows no difference. If the nutrient is available, it is fertilizer, and for that
reason, all nutrients are fertilizer.
Synthetic Fertilizer, What Is It?
Here is the truth. There is nothing new under the sun. That is even what the bible
says in the Book of Ecclesiastes. Man doesn’t create anything new, he only changes things.
Such is the case with fertilizer. Humans take elements already found in nature, and combine
them in a way to make them more useful. So after changing nutrients in a factory, making
them easy to store in sacs, and making them easy to apply in fields, man has made
“synthetic fertilizer.”
Nitrogen is one of the most important nutrients for crops. There is plenty of nitrogen
in the environment; in fact, 79% of the air we breathe is nitrogen gas, in the form of N2. If
there is so much nitrogen around, why then is it so scarce when it comes to growing crops?
The answer is this: Crops can't use nitrogen in the form of nitrogen gas (N2). Nitrogen
comes in many forms. Nitrate (NO3-) or ammonium (NH4-) are the forms which plants can
use. While usually in short supply, they occur in soil or water naturally.
7
A Maize Plant Explains To His Farmer What Kind Of Food It Prefers
To make synthetic fertilizer, humans take nitrogen gas (N2) and change it into nitrate
or ammonium, which can then be added to fields. The most important thing to understand,
however, is that nitrogen gas is made of two nitrogen atoms (that’s why it is written “N2”)
and those two nitrogens are held together by a very strong bond.
8
Nitrogen Gas Is Everywhere, But Its Chains Must Be Broken First
Before we can make synthetic fertilizer we have to break that bond, using a large amount
of energy. That energy is usually supplied by petroleum oil. Therein lies the reason why
synthetic fertilizer can be so expensive. When oil is expensive, so is synthetic fertilizer.
It Takes A Lot Of Petroleum Fuel To Make Fertilizer
Now we know why fertilizer is expensive, but why is petroleum fuel so expensive? It
is simple. The demand for oil is very high, and the supply is getting smaller. There is only a
limited amount of oil in the world, and many people are predicting the world will start to run
out of oil in the next century. Some say it will happen in 50 years, some say even 30. The
question is not if but when oil will be very scarce. This means that the price of oil will only
rise, generally speaking, in the future.
With the price of oil climbing, so will the price of fertilizer rise. Unless people figure
out ways to make more money, they will either become poorer or have less food.
If
governments continue to subsidize fertilizer, they will become poorer, unless they
have some other way of earning money. This means less money will be available
for schools, hospitals, development programs, or government workers salaries.
“Kawe pano nkha tose” or "we’re all in the same boat", as the Tumbuka proverb goes. In
this case, the leak in the boat is the rising price of fertilizer. If we don’t work together to
patch it, the whole boat can sink, and we’ll all go down together. This makes it very difficult
for countries to move forward.
9
We’re All In the Same Boat
This is not a book about problems. Its purpose is to provide solutions. There are two
main solutions in dealing with expensive fertilizer:
1.) Find ways to make more money so we can continue to buy it.
2.) Adopt management practices that reduce the dependence on synthetic
fertilizer.
For solution # 1, a whole separate book could be written on income generating
activities for rural areas and developing countries on the whole. That book is coming. For
now, this book will focus on solution # 2—other beneficial farming practices.
These
practices will empower the farmer with the capacity to produce the same amount of food
using less synthetic fertilizer, or grow more food than before, using the same amount of
fertilizer bought in the store.
Before we continue, the most important thing to know could be this: Growing food
does not depend only on how much synthetic fertilizer is available for a family. Look at the
growth of one crop on a field where the soil varies.
You can put the same amount of
synthetic fertilizer throughout, and find that you get different yields of food. Why is this the
case? What makes nutrients available in a soil, so that crops can use them? What other
factors influence crop growth besides nutrients? Most importantly, what can a farmer do
with his own two hands, a hoe, and many days of sweat to make sure his family is fed,
regardless of the future of synthetic fertilizer?
10
PART TWO
Legumes
We have learned that there is no new thing under the sun.
Man doesn’t create
nutrients; he just changes them in a way so he can put them into sacs. Legumes are a type
of plant that does similar work. They take nitrogen from the air in the form of N2 gas, and
then do the same thing that humans do in factories using plenty of petroleum: legumes split
the strong bond between the two nitrogens, and then change the nitrogen into a form that
can be used by crops. It is almost like a miracle, with the farmer not doing much except for
planting the legume. The plant’s roots will manufacture fertilizer all by itself. Remember the
Tumbuka proverb: “Its only miracles that come by themselves!”
It is actually bacteria, tiny organisms you need a microscope to see, that do all the
work. The roots of the legume attract bacteria to their roots. The bacteria will then build
their little “houses”, commonly known as nodules, on the plant's roots. It is in these nodules
that the nitrogen from the air is “fixed” and later changed into NH3 and NH4 nitrogen. That
nitrogen can be used by the legume plant, or can be left in the soil for other crops when the
legume is left to decompose in the soil. A farmer can always know if legumes are producing
fertilizer by digging up a sample and looking at its roots. If you see root nodules, this is the
miracle at work! Don’t be fooled, however, for some crops will develop root nodules when
they are attacked by disease. Tobacco, for example, is not a legume; it is just susceptible to
root knot nematodes. To be sure the nodule contains nitrogen-fixing bacteria, split it open –
a true nodule will be pink inside.
There are many choices of legumes a farmer can plant. These can be split into two
main groups. In the first group are plants that add soil fertility and give you food at the
same time. The second group of legumes is planted with the sole purpose of improving soil
fertility.
The first group includes groundnuts, beans, peas, pigeon peas, and soybeans.
After harvesting the food from these crops, the remaining plant materials can be left to
decompose and provide food for microorganisms, which release to the soil all of that new
nitrogen stored in the plant for other plants to use. Whichever crop is planted after the
legume crop stands to benefit from the extra nitrogen that has been taken out of the air and
put into the soil.
11
The Nodules On Roots of Legumes Are Like Factories of Nitrogen Fertilizer
Legumes in the second group, known as cover crops, are not food for humans, but
their main purpose is to feed the soil. Tephrosia (gulinga), mucuna (karongonda), crotilaria,
and faidherbia (msangusangu) are all examples. They are fast-growing and produce ample
biomass, or green matter rich in nitrogen.
They can either be planted with food crops,
around field borders, or in crop rotations.
Tephrosia, for example, can be planted in
between maize stations, and provided they are planted early enough, can be left to grow in
the rainy or the dry season that follows. The leaves can then be cut and left on top of the
soil to decompose, incorporated directly into the soil, or gathered into piles to decompose
into compost manure.
12
One thing is very important to remember here. Leaves of legumes are very high in
nitrogen, but if the leaf dries out in the hot sun, most of its nitrogen will also
evaporate. This is true for all green leaves, which have some nitrogen. IF THEY ARE
INCORPORATED INTO THE SOIL WHILE STILL GREEN, NITROGEN WILL BE ADDED TO THE
SOIL. If they are collected into piles and kept moist, nitrogen will stay in the pile and can be
added to the soil later. But if they are just left to dry, most nitrogen will be lost.
Residues Left To Dry Lose Nitrogen
For this same reason, nitrogen fertilizers (urea, 23-21) should not be applied to dry
ground.
If they are applied to dry ground, nitrogen can be lost through volatilization.
Nitrogen fertilizers should instead be covered with soil, preferably moist soil.
Many legumes grow naturally as weeds in farmers’ fields. If they are not in direct
competition with your crop, why slash or weed them? They should be your good friend! If
you find them, just let them grow. That way they can be adding nutrients to your soil while
your crops are taking nutrients away. Just think, if you found some food crops growing on
their own, without inhibiting other crops would you weed them? No, because these crops,
sprouting on their own, also feed you. Now, if you find a legume, you can know that it is
also a crop – it feeds the soil! If year after year you leave wild legumes and let them go to
seed, there will be more the next year – they will multiply with no work on your part. They
will still be weeds but they are weeds with a use. They can out-compete other weeds that
have no uses. That way if you are late to weed your crop you can say, “No problem! My
weeds have a use – they add fertilizer to my soil!”
Several systems are recommended for inter-planting legumes as green manures or
cover crops. One common method is as follows:
13
TEPHROSIA AND MAIZE
Nov.-Dec.: Plant maize or cassava 90 cm apart on ridges 75-90 cm apart. In between
each station, plant the legume. The advantage of Tephrosia or Pigeon Pea is that it sprouts
well after direct sowing. Plant at two stations 30 cm apart, three seeds per station. For
Mucuna, do the same, using two seeds per station. For Crotolaria, make a furrow and plant
seeds 10 cm apart. Other tree species can be planted in between the 90 cm maize/cassava
stations but they might be better to plant in nurseries before the rainy season starts.
Examples include Sesbania, Senna (Keshya). or Faidherbia (msangusangu).
Jan.-Apr.: Weed and care for intercropped legumes as you would other crops.
Apr.-Nov.: Leave legume to grow until the next planting season.
Nov.:
Cut legume and incorporate into soil with ridge preparation.
Be sure not to
incorporate branches – use them for firewood instead.
Dec.: Plant field for new rainy season. The field can be planted the same as above for
successive seasons.
This system can significantly boost soil fertility, especially if used year after year.
14
URINE
Urine can be a valuable substitute or supplement to synthetic fertilizers. The exact
same chemical sold in bags as urea fertilizer is present in urine. The only way urine is
different is that urine also contains other nutrients besides urea, such as phosphorus and
magnesium, plus water. Also, the concentration of urea in synthetic fertilizer is stronger
than that of urine. Urea sold in fertilizer sacs is generally 45%, whereas urea in urine is
generally about 15%.
In the same way that too much urea can burn crops, urine poured directly on crops
will burn the leaves. A general guideline to follow is: one part urine to five parts water –
mixed together well. You can then take a cup and pour a little bit directly over the soil at
the roots.
People are always asking, “Yes, urine can work, but how many acres can it really
supply with fertilizer?” The answer would depend on many things, but, theoretically, urine
from two people can replace synthetic urea fertilizer enough to fertilize 1/10 acre of maize
(see footnote). Most families in Africa are much larger than two people, meaning it could be
possible for a family of ten to fertilize ½ acre of maize, saving a lot of money. Maize, out of
all food crops, demands the most nitrogen. The potential for completely replacing synthetic
nitrogen using urine could be even more significant with other crops.
d
With
that
said,
here
is
a
serious
question: After buying a bag of urea, do
you then come home, open the bag and
pour the contents down the hole of your
toilet?
Do you empty the bag in the
bushes when no one is looking? If you
don’t do that with urea, and think it is
crazy, then why would you just waste
your
urine?
It
can
be
excellent
fertilizer.
While the nitrogen in urine is the same chemically as urea, the method of fertilization
is very different. With urea, the fertilizer is applied only once or twice, but with urine, it is
little by little every week or every two weeks. You could probably fertilize less often than
that, but the stored urine may start to smell bad. Urea is commonly placed in between
plants for maize cultivation, while with urine, you can pour the urine/water mixture directly
15
at the roots. Urine can be used in the same way as urea with regards to which plants to
fertilize.
Urine Can Be Great Nitrogen Fertilizer: Just
Why Waste Such a Valuable Resource Just
Add Water
Because It Smells A Little?
------------------------------------------------------------------------footnote---------------------------------------------------------------------------------------1 Bag of Urea= 45% Nitrogen
Recommended Application Rate= 0.8 Bag or 40kg/acre of maize
45% of 40 kg of Urea= 18 kg of Nitrogen/acre
One farmer, on average urinates 10g of nitrogen per day. One season or possible fertilization period for maize is 90 days, so 900 grams, or
approximately 1 kg of nitrogen could be supplied by one person/season
2 Adults could potentially supply 2 kgs of the nitrogen needed per season. 2/18=1/9
Hence theoretically, close to 1/10th of an acre or 1/10th of a fields nitrogen fertilizer needs could be met with urine.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------
16
Animal Manure
Manure from livestock animals can also be used as a nutrient amendment. Excess
nutrients like nitrogen and phosphorus and potassium from the animals’ food is present in
the manure.
Animal manure that can be used includes chicken, duck, goat and rabbit
manure. Fresh manure is especially high in nitrogen and may burn crops if applied fresh.
Fresh manure should therefore be
composted before it is used on crops.
This is a popular practice amongst animal farmers
who want to make good quick use of the nutrients available
in animal manures. The way to make it is as follows:
1. Fill a bucket, basin, or any other container with fresh
animal dung.
2. Pour water in the container until it just covers all of the
manure.
3. Let the whole mixture soak for 21 days. During this
period the slurry should be stirred once a day.
4. After 21 days, filter the contents and take the
concentrated filtrate and dilute it a further 1: 20 (1 part
liquid manure to 20 parts more water). Use this to water
your crops, pouring about 1 cup above the roots.
High carbon materials such as dry
grass or maize cobs can be added to
the fresh manure which is then left to
decompose.
be
used
Fresh manure can also
as
a
high
nitrogen
component, in place of fresh green
residues, for other composts.
"Compost
Composting
Manure"
helps
to
(See
below.)
save
the
nutrients in the manure so that it can
be
applied
to
fields
as
needed.
Manure left to dry out in the sun loses
many of its nutrients.
Animal manures are also a
great source of organic matter for the
soil, which helps to improve the
structure and overall health of the soil.
A simple way to make composted cow
or pig manure is to add straw or maize
cobs to the kola and let the manure
decompose in place. Manure collected
from the kolas of ducks, chickens,
Some claim that this method gives results similar to some
synthetic fertilizers. Used in conjunction with synthetic
fertilizer, it might even boost yields further. Why not try it
and see for yourself!!
goats and rabbits can be added to a
compost pile.
Another advantage of
composting manure is that the high
temperatures created by composting
can kill many disease-causing pathogens or parasites that may be present in the animal
manure.
17
Compost Manure
All of the nutrients a plant takes up don’t get harvested as food.
These are the
nutrients that are stored in leaves and stalks and stems of crops. Here in Tanzania, those
“crop residues” usually get left behind on the field to be burned or buried at the start of the
next planting season. Upon burning, some nutrients like phosphorus, potassium, calcium
and magnesium are returned to the soil in the ash. But other nutrients like carbon and the
all-important nitrogen are lost by burning. But what if someone told you that there was a
way to save all of the nutrients from the residues so that they could be used again by the
next crop?
There is a way! It’s called composting!
When you make compost you are
gathering up the unused parts of the crop and concentrating their nutrients so that they can
be reapplied to your crop field in the future. That way, the crop nutrients that don’t get
eaten as sima, for example, get used to grow more maize, rather than “going up in smoke.”
Compost is a cheap way to add to soil fertility, or to decrease the amount of fertilizer you
have to buy.
Is Burning Away Nitrogen In Fields Like Burning A Pile Of Money?
There are some simple things to understand to effectively make compost.
It is
microorganisms that break down the residues to release nutrients to make compost. So
really, making good compost is just about making a nice place for microorganisms to do their
18
job of decomposition. In order to save the most nitrogen, residues should be gathered up
into a pile while they are still fresh. You’ve seen that residues left out in the sun quickly turn
brown. Once the residue turns brown, it means that most of the nitrogen that was in the
residue has already been lost to the air. So if you compost fresh residue, your compost will
have more nitrogen in the end.
Microorganisms need both carbon and nitrogen to work efficiently. To get the fastest
and most complete decomposition of residues, a compost pile should be made up of a lot of
fresh residue, some dry residue, some topsoil (to supply the microorganisms) and the pile
should be kept moist but not drenched. By doing this you are providing a good environment
for decomposition by providing nitrogen (the fresh residue), carbon (the dry residue), water
and air for the microorganisms.
If you have a lot of dry brown residue but little fresh
residue, you can still compost it by adding a high-nitrogen substitute such as animal manure
or urine. Dry residues will eventually decompose without an added nitrogen source but it
will take longer and the resulting compost will be lower in nitrogen.
Another way of thinking about making microorganisms happy is this - making a good
compost manure pile is like eating ugali with mboga. The white ugali is like all the dry
residue you add to your pile, but a good ugali dinner is not complete without mboga – so the
fresh, green, high-nitrogen materials are like relish for the microorganisms.
Here we see another use for urine. If you don’t want to take it to your field, just pour
it on your compost manure pile to aid microbes in decomposition, rather than wasting it in
the chimbuzi.
Making Compost: Feeding Microbes Sima and Dende
19
Compost manure is very easy to make. The first step is to gather the materials: dry
brown residues (carbon-rich), fresh green residues (or other nitrogen-rich material) and
topsoil or finished compost (to supply the microorganisms). These materials are then mixed
together in a pile about 1 meter tall and 1 meter wide. The pile should be kept moist and
turned (mixed) every few weeks. Decomposition time is on average about 2-4 months but
depends on weather conditions and various other factors.
MINI COMPOSTING
Making small piles of compost manure in your fields is known as mini-composting.
Instead of spreading out weeds to dry in the valleys next to your ridges, you can
gather fresh, green weeds into miniature piles between the ridges throughout
your field. Just cover the piles with a little bit of topsoil and that’s it. Most of the
nitrogen from the green leaves of your weeds will now return to the soil instead of
being lost to the air. The weeds will also not re-germinate in the valleys when
they are gathered into mini-piles.
After Weeding, Instead of Spreading
Why not make mini-compost piles to
Out Residues…
save nitrogen!
Compost provides benefits aside from just adding nutrients.
important benefit, is added organic matter (OM) to the soil.
Perhaps the most
OM is extremely important for
a soil to be productive. It increases the soil’s ability to hold water, thus prolonging the
20
growing season. It makes soil softer, thus enabling plant roots to spread deeper into the
soil. It is the key factor in preserving soil structure, thereby preventing soils from getting
compacted or powdery and then getting eroded by wind or washed away by water.
It
stimulates microbial activity, which releases nutrients and carbon dioxide. Remember, plants
need carbon dioxide to make food. They breathe this gas from tiny holes called stomata on
the underside of their leaves.
Why are stomata on the underside of the leaves?
It is
because a large part of the carbon dioxide plants breath comes from the soil. A soil with
little OM will produce little carbon dioxide, but a soil high in OM will produce more carbon
dioxide, which escapes from the soil so plant leaves can use it.
Leaves Breath Carbon Dioxide From Soils High In Organic Matter
In summary, it is easy to lose certain nutrients, such as nitrogen and carbon. They can
evaporate if green residues are left to dry, or they can literally go up in smoke when people burn their
fields. With a small amount of effort, however, these valuable elements can be saved. Making
compost manure piles is a great way to recycle nutrients from one crop to the next and add OM to the
soil, which can help in so many ways.
21
PART THREE
Availability Of Nutrients
You can be the owner of a fertilizer factory, but still your crops might fail because
they don’t have access to your nutrients. Any nutrient, whether it is from fertilizer, manure,
urine, or legumes must be present in the soil in a situation where the nutrient is available or
ready to be taken up by your crop.
WET SOIL ( DAMBO SOIL)
A very wet soil will mean that nutrients can be leached away either by washing off the
surface, or going down too deep in the soil, below the reach of plant roots. The main reason
is that most nutrients become dissolved in water and therefore move with water.
This
enables plant roots to get vital nutrients while they are drinking water. Too much water,
however, will sink deep into the soil, taking nutrients with it. Those nutrients are then no
longer available to plant roots. Still, wet soils can be very different. A very sandy wet soil
will hold nutrients differently that a very clayey soil or one with high OM. This is due to a
concept called “cation exchange capacity” or we can say “nutrient holding capacity.” This is
how it works: Every piece of soil has its own electric charge (like a magnet). All nutrients,
when dissolved in water also have a charge – either positive or negative. Soil particles are
usually negatively charged. This means that the negative soil particles will be attracted to
the positive nutrients and hold them, but negative nutrients will not be attracted to or held
by the soil.
Soil Particles Are Like Magnets With Negative Charges. Nutrients With Positive Charges
Will Be Held, But Nutrients With Negative Charges Will Not
22
Sandy soils will have fewer charges than a soil with more silt and clay. Sandy soils
will also have less negative charges than a soil higher in OM.
If you didn’t understand
anything written above about charges, positive and negative, don’t worry.
The most
important thing to know is this: with a wet soil, there is a danger of washing away useful
nutrients. If you have more OM or clay in your soil, that soil will be able to hold more
nutrients so when there is plenty of water, it won’t wash away all of the nutrients. Sandy
soils, however, cannot hold many nutrients, so any nutrients that you apply will be easily
washed away.
If you have a sandy soil that is very wet a lot of the time, the best thing you can do is
make sure to add organic matter. Instead of burning, let residues decompose over time.
You can also add animal manure or compost manure to increase OM. You have just read it
is OM and clay that can hold many nutrients. It’s not practical to add clay to a soil, but you
can do your best to add OM.
Besides holding nutrients, there is another thing OM does for wet soils. It builds soil
structure, which allows water to drain faster and enables roots to fill air spaces created by
soil aggregates. A soil low in OM will just turn into a wet mass of mud that is too wet for
roots to grow.
Soil With Organic Matter Has Stable Aggregates, Or Pieces of Soil That Make It Easy In
Wet Soils For Air To Enter and Water To Drain Through Easily
Apart from nutrients just washing away with too much water, there is one other
important way wet soils loose nutrients. It is a chemical reaction known as “denitrification.”
When there is no air, or too much water, microbes will turn nitrate-nitrogen (NO3) into
nitrogen gas (N2), which escapes from the soil and is lost.
23
A
perfect
denitrification
is
example
in
the
of
“chungu”
areas, or low-lying valley crop fields.
Any legume can be used as a cover crop. Here is one
example of a relay planting system:
You would think that because of so
AUGUST-SEPTEMBER:
Slash weeds and gather
them into compost piles, in preparation for maize
planting.
SEPTEMBER- OCTOBER: Plant maize crops in rows,
Sasakawa Global 2000.
Plan for irrigation if
necessary.
OCTOBER-NOVEMBER: Care for maize crop.
DECEMEMBER: Right before the maize crop starts
to mature, loosen soil in between the rows and
under-sow a legume, such as mucuna, sesbania, or
pole beans.
JANUARY- APRIL: During the rainy season, let the
legume grow and spread.
Its roots will add
nitrogen to the soil in the row where it is planted,
and its leaves will also be rich in nitrogen.
MAY: Slash cover crop and compost. Be sure to
mark the rows where you had it planted.
SEPTEMBER: Loosen soil in the rows where you had
your legume planted and plant your maize crop
again. Repeat this over the years, just shifting your
rows back and forth between food crop and cover
crop.
available nitrogen for crop growth, but
much organic matter, there would be
you will find that it is very tough to
grow maize or other nitrogen loving
crops without nitrogen fertilizers. This
is because whatever nitrate (NO3)
that is not taken up by weeds
becomes “denitrified” in the rainy
season when it is very wet in the
dambo areas. This nitrogen turns to
gas and leaves the soil. There might
be nitrogen that does not turn to N2
gas and leave the soil, but weeds
usually take it up. Farmers make the
situation
burning
worse
all
the
by
slashing
residues
in
and
the
“chungu” before planting maize. By burning, the nitrogen just escapes into the air. You
might then hear that same farmer who burned complaining about the high price of nitrogen
fertilizers. It is the same as punching yourself in your own eye, and then complaining that
your eye hurts!
One solution for the chungu farmer is this:
to save nitrogen, aside from not
burning, the farmer can plant what is known as “cover crops.” These crops are legumes that
require little care.
They just grow and fix nitrogen to the soil.
The advantage in this
situation is that the type of nitrogen that a legume fixes is ammonium-nitrate (NH4+), which
is not lost by denitrification, as is nitrate (NO3-) in very wet soil in the rainy season.
DRY SOIL/UPLAND SOIL
Unlike a wet soil, a dry soil will not lose most of its nutrients due to leeching or from
denitrification. Most of the fertility losses from upland soils are due to EROSION. An upland
soil is much more exposed to the forces of wind and water than a dambo soil surrounded by
hills. Wind can be a serious factor in blowing topsoil away. Water can be a powerful force
in washing away important nutrients. As the Tumbuka proverb says, "If you want to kill the
snake, crush its head," ("Kukoma njoka nkudhinya mutu.")
--if you want to solve the
problem of low soil fertility, first make sure you have soil! First, prevent soil erosion.
24
It seems like such a simple thing to understand—that without soil we can’t grow food.
Then why don’t people do more to prevent soil erosion? Part of the reason is this: While it
can be very serious, soil erosion usually happens very slowly. The wind blows away one
small cloud of dust at a time, or the water carries away just a bit of soil at any one time, just
enough to make the water look cloudy. Farmers look at their fields and see little change.
It’s like watching hair grow; you know it’s growing but you can’t see it happening. But the
truth is, if you take a picture of a person now and 4 months later, his hair will look different,
you will notice. The same holds true for a field. Measure the depth of topsoil now and 4
years later, and in most cases you will notice a difference.
Another mistake farmers make is failing to distinguish topsoil from subsoil.
They
might be satisfied as long as they can get out to their fields and make ridges. They might
think that as long as they can pull a hoe through it, it is soil. They say, “Look! Look at my
ridges. I have ridges. There is no soil erosion here.” Yes, the farmer is correct—there is
soil. But it is subsoil! There is a big difference between topsoil and subsoil.
You, Farmer—Is It Topsoil Or Subsoil That You Till?
Every soil is made up of layers, commonly known as soil horizons. You can see them
when there has been a trench cut for irrigation or for building a house. In every soil, we can
pick out 3 main horizons- A,B, and C. The bottom horizon, the C-horizon, is the layer with
the most rocks, since it is deeper it is less weathered or broken down into smaller pieces of
soil. The middle layer, the B-horizon, is composed of more soil, but is mostly clay and has
little organic matter (OM). This B-horizon is usually more reddish in color that the layer
above it. The upper layer, the A horizon, is every farmers best friend. It is the root zone for
most crops. It is usually darker in color because it has more organic matter.
That OM is
the source of many plant nutrients, and it is also food for microorganisms that makes many
25
more nutrients available to crop roots.
The OM in the A layer also helps to create soil
structure, which helps plant roots spread, as we’ve read previously. In short, the A layer, or
“topsoil”, as it is commonly known, is most supportive of productive plant growth.
It pays to conserve topsoil
It takes a long time for the A horizon to form, but it can be quickly destroyed by
erosion. This is especially likely when cultivating steep slopes or in windy areas. Unless
measures are taken to prevent soil erosion, the farmer is left with less topsoil, or a thinner A
horizon, year after year. The farmer might not notice, because he/she can still use the hoe
to form ridges. These ridges, however, are often made up of mostly subsoil from the B
horizon, with only a little topsoil mixed in. This means few nutrients from the soil in the
farmers ridges will be available for his/her crops, requiring the farmer to be dependant on
fertilizer. The subsoil making up his ridges is also poor in holding water, meaning in drought
years, the crops will be more likely to fail, potentially bringing serious hunger. At the time of
this writing, hunger was already plaguing many parts of East Africa, and there was still 3
months left before the next harvest. Is the problem here hunger? Of course it is, but an
even deeper problem might be soil erosion, which is causing that hunger. So let’s solve the
problem that’s causing problems. Let's kill the poisonous snake by crushing its head.
Soil erosion caused by water can be prevented by first protecting the soil from the
impact of raindrops, and second, taking measures to slow the flow of water once it gathers
on the soil surface. In other words, there are two lines of defense in protecting soils from
26
erosion. People seem to think that by making contour ridges they have done a good job in
conserving topsoil. Oftentimes people overlook the crucial first line of defense: protecting
soil from the impact of raindrops. Just think of a game of soccer. All players act as
defenders. To ignore the first line of defense in soil management is like the midfielders in a
game just walking around nonchalantly, and letting the ball roll past them, leaving the
defenders and the goalie--the last line of defense-- to bear the whole burden of preventing
goals. A good team, however, has all the players acting as defenders.
Raindrops Beating the Soil, but Only When It is Unprotected
The force of raindrops is surprisingly strong. Just observe bare ground at the start of
a real downpour. You will see bits of dirt being kicked up by the raindrops. If you wait a
little longer to see the water flow, you will see that now those little bits of loosened soil are
being carried away with the water. If there had been some kind of protection over the
ground, like some residue, or an overhanging tree branch with leaves, that soil would not
have been loosened. The flowing water a few minutes after the rain started would not have
carried the soil away. In other words, just because there is flowing water does not mean
there will be soil erosion. The soil must be loosened first before it is carried away.
Prevent the loosening and you will prevent the erosion. Just look at an irrigation
ditch or small stream that runs with clear water. There is no dirt in that water because no
soil was loose enough for the water to carry the soil away.
It is in the farmer's best interest to prevent loosening of his soil by raindrops. To
protect the soil, just keep it covered. Residues, instead of being burned, can be left on the
27
soil surface to lessen the impact of raindrops. Trees can be planted to provide a canopy to
protect the soil. Crop plant spacing is very important in preventing soil erosion – they should
be planted as close as possible to provide an effective ground cover. Intercropping with
legumes such as Gulinga, as explained in the “legumes” section can be useful if the shrubs
are left to grow for when the soil is left fallow in following years. Try to imitate the forests
found in nature - there you’ll see very little soil exposed and therefore very little soil erosion
taking place.
If the first line of defense fails, then rely on the second. Slow the flow of water so it
goes into the soil before it has a chance to carry away your soil. All ridges should be aligned
according to the slope of the field. They can be aligned by simply using one’s own eyes and
making sure they don’t run downhill, or better yet, by using a line level or an A-frame.
Multi-Purpose Trees Also Make An Excellent Hedge To Protect Fields
Boxed ridge ends are also very effective in preventing erosion. At the ends of all of
your ridges, just make one ridge going across tying all of you ridges together. Hedges are
another great strategy. Vetiver grass or small tree species such as Gulinga or Sesbania can
be planted along contours or hedgerows, spaced throughout the field.
The number of
marker ridges needed will depend on the slope. Soil in fields next to footpaths is especially
vulnerable to erosion because water moves so fast along the paths.
around the field that borders the path is recommended.
Planting a hedge
Plant hedges that give more
benefits than just preventing erosion – vetiver grass, for example, can be trimmed for
excellent roofing grass! Keshya wa maluwa (Senna), another possibility, produces flowers
28
that are good for honeybees and also beautify your surroundings. Pigeon pea can be a good
hedge and produces edible beans for several years. Hedges can also be planted anywhere
where there is danger of wind erosion. Again, multipurpose trees can be planted. Why not
fruit trees?
TO BURN OR NOT TO BURN…
Burning of fields in preparation for planting is a very popular practice in Africa.
Burning is popular for several reasons. First off, burning of slashed vegetation as well as the
roots from that vegetation makes the labor of hoeing easier because there is no vegetation
holding the soil together or making a barrier between the soil and the hoe blade. Second,
minerals such as phosphorus and magnesium remaining in the ash after burning of residue
provide a quick nutrient boost to newly planted seeds. This quick but short-lived supply of
plant-available nutrients can give the new crop a good start in establishing itself. Thirdly,
farmers fear that residues left on the field attract certain pests and could exacerbate disease
in the newly planted crop.
For these reasons (there may be others as well), Malawian
farmers have learned to love the sight of a “clean” field for planting – one with no residue,
with only overturned soil waiting to receive lines of seeds.
There are, however, disadvantages to the practice of “slash and burn” agriculture.
For one, burning is very detrimental to soil structure and health. Residues that would have
contributed to OM are destroyed; burning also destroys OM already in the soil in the form of
humus. Roots that normally hold the soil together are also burned. This leaves a soil with
little ability to hold water and nutrients and little ability to resist erosion. Soil that has been
hoed and left bare is exposed to the destructive forces of the falling raindrop and the
blowing wind. As well, it is left to heat up in the sun, often leading to high temperatures
detrimental for beneficial soil organisms. Residues, on the other hand, protect the soil by
absorbing the impact of the raindrop, keeping the soil from washing away with water or
blowing away in the wind. They protect the soil from the hot sun and add OM.
While some mineral nutrients such as phosphorus and magnesium remain in the ash
after burning plant residues, others are lost altogether upon burning. The most important of
these is nitrogen. The nitrogen from plant residues that would normally be held in
the OM is lost completely when the residues are burned. Carbon, also a major
component of OM is lost upon burning of residues.
Sulfur, another essential
nutrient is also lost. Burning residues year after year, therefore, results in constantly
decreasing levels of nitrogen and carbon in the soil, forcing farmers to purchase fertilizer in a
bag in order to grow almost any crop. Eventual complete dependence on synthetic fertilizer
is one of the prices you pay for burning.
29
Burning Residues In Fields: Some Nutrients Stay, But Carbon and Nitrogen Go Away
One option other than burning or just leaving slashed residues to cover the field is to
gather the residues into heaps while they are still green and allow them to compost. This
way, residues are cleared from most of the field but the nutrients, including nitrogen and
carbon are saved and can be reapplied to the soil. Roots are left to decompose in the soil
and add OM while they hold the soil together and protect against erosion. Compost piles
also address the pest issue as decomposition leads to high temperatures within the piles
above which mice or other pests could tolerate. (Also see "Mini-composting".)
Another option for saving nutrients, or another alternative to burning is EARLY
RIDGE PREPARATION. Directly following harvest, while some residues are still green, you
can make new ridges and bury all residues during ridge preparation. These residues will
then have ample time to decompose and the nutrients will be available to crops planted at
the beginning of the next rainy season. Another advantage is that when the next rainy
season comes, the farmer can just plant! Very little work is involved because ridges have
already, for the most part, been formed. To make the most of EARLY RIDGE PREPARATION,
a cover crop can be undersown late in the rainy season.
That way, when residues are
buried, there will be nitrogen-rich green material available. Here is an example:
30
This practice is very useful in adding nitrogen to crop fields, especially if a legume
is relay planted as in the following example:
DECEMBER-JANUARY: At first rains, plant a field crop, such as maize.
FEBRUARY-MARCH: Plant mucuna (karongonda) or any other cover crop under or
in between maize plants or stations, sharing the same ridges.
MAY-JUNE: Harvest maize.
JUNE-JULY: Right after harvesting, slash all remaining vegetation (dry maize
stalks, green cover crop leaves and any other weeds). Lay all residues in the ridge
valleys. Then bury the residues while you make new ridges. Do not wait until the
hot season to do this. Take advantage of early ridge preparation!
OCTOBER-NOVEMBER: Just laugh at your other friends while they spend hours
making their ridges in dusty, dry ground. You can just rest because your ridges
are mostly ready. (Some banding might be needed.)
DECEMBER-JANUARY: Plant your next crop with the new rains.
With the above system, rather than losing nitrogen and carbon by burning,
you will save them in a way that will be useful for improving the fertility of your
fields. This done faithfully year after year will significantly increase crop yields.
31
Bio-Intensive Mini-Farming
(From: Creating an Edible Landscape)
The Circle of Sustainability – Sustainable Diet Production
How does intensive gardening fit in with soil fertility management? In a word:
perfectly! Bio-Intensive garden beds encourage precise plant spacing, a dense canopy,
companion planting, healthy, deeply prepared, compost rich soil teeming with natural life
and biological systems in place. Basically, a bio-intensive garden bed is an “annual guild”
created to mimic nature, and to take full advantage of all the power nature provides in the
growing of nutrient dense foods in astonishingly small spaces.
Bio-Intensive garden beds can provide two to three times as much food on ½ to 1/3 the
land area of conventional gardens. Just as in permacultural design, we are maximizing
nature both to its, and our own, benefit. Permacultural guilds and water management
techniques can support the fringes of the property taking advantage of height, space and
shade in the corners while bio-intensive is the tool to employ within the open sunny spaces.
These are both great tools to have in the toolbox as we look to build soil fertility in the fight
to build immune systems and to strengthen both people and their communities.
Deep Soil Preparation
The average agricultural field is tilled and aerated to the depth of the equipment used
to work the land. At best, this means soils are tilled to roughly 20 cm, or the length of the
average hoe blade. Over time, after successive tillage to the same level, a near
impermeable “hoe pan” is created which blocks the movement of air and water through the
soil profile, as well as the growth of the roots of our crop plants. If plant roots aren’t
encouraged to go deep (which they can only do if there is good air-water dynamics in place)
then they must be planted farther apart so as not to compete with their neighboring plants.
As they must be farther apart, sunlight will easily reach the soil surface causing weed seed
germination, evaporative moisture loss and weaker plants overall.
By preparing the soil deeply (double digging) and breaking through that compacted
subsoil layer, plant roots will be able to go much deeper – in some cases as much as 5-6 feet
deep! This is what allows us to place plants closer together in a smaller space and where
we begin to approach those promised high yields. It has been proven that a mere 4%
increase in root health will give a corresponding tripling of yield per unit area. It all starts
with proper and deeper soil preparation.
Close and Precise Plant Spacing
As the soil is now well aerated to a depth of at least 2 feet - and has been amended
with copious locally made compost to add to its moisture levels, microbial health and
nutrient level - it can be planted with greater and closer precision. Each vegetable, grain or
fruit plant will have a certain root spread and growth habit. It will also have its own unique
canopy of leaves and stems. The ‘master charts’ found in How to Grow More Vegetables can
serve as your guide here and you are encouraged to study this text in depth.
Observe. Does Nature ever plant in rows? No. So rather than in rows, with biointensive gardening, plants are spaced hexagonally (much like the cells in a honeycomb
which is a brilliant example of nature’s space saving design) to allow for a full and complete
32
leaf canopy within which plants will maximize their space yet not compete with each other
for nutrients, moisture or carbon dioxide.
Bed Dimensions – 1 meter wide
The dimensions of these permanent garden beds and paths is an important detail.
While bed length is purely up to the individual landscape limitations (6-8 meters is a good
and convenient length however), it is the width which must be watched carefully. Once the
bed is fully texturized - or double-dug to a 2 foot depth – it is never to be walked on again.
Each time you walk on the soil – say when you must weed between the rows of the
conventional garden – you are pressing out the air and compacting the soil, seriously
jeopardizing root health which, as has been pointed out, is critical if we want to achieve high
yields. So a width of no more than 1 meter is ideal as it is then possible for the gardener to
reach the center of the bed and its plants from either side.
Healthy Microclimate
The closed canopy in the garden bed will capture and hold moisture and carbon
dioxide. The carbon dioxide comes from the rich and diverse microbial life found in the
compost you’ve added prior to planting. Carbon dioxide is the first ingredient in the process
we know of as photosynthesis whereby carbon and water mix to form sugars for plant
growth and oxygen for us via the chlorophyll found within the structure of healthy leaves
and stems. Moisture needs are also diminished greatly due to an increase in bed shading
and a decline in evaporative water loss. This stimulates greater growth and promotes
thriving healthy plants which feed people; resist insects and diseases (it is well known that
insects and diseases will prey on weak plants); produce seed acclimated to local growing
conditions; and, provide copious amounts of material for compost.
Compost
This was discussed in detail earlier, but it should be mentioned again that this
valuable soil conditioner is also a teeming source of valuable microbial life. In fact, over 6
billion beneficial microbes are found in just one tablespoon of mature compost. These
microbes create the much needed carbon dioxide and carbonic acid which allows for the
creation of plant sugars and plant nutrients. For example, phosphorus is changed into the
plant available form phosphate due to the carbon dioxide found in the soil. These microbes
are also responsible for a natural increase in growth hormones, plant vitamins and
antibiotics. So while the bio-intensive method means more plants per unit area due to soil
depth and hexagonal planting style, it also means healthier, higher yielding plants as well.
Compost is one of the simplest and most natural things we can do to improve the health of
the soil and the quality of the food, and by extension the people, generated from that soil.
Mini Farming
It is when all these soil fertility processes and techniques are combined that we begin to see
how we have gone beyond mere gardening and are indeed looking at “mini-farming” right
outside the back door. Real income can be achieved along with real increases in quality
food. Land that would have otherwise laid fallow or which has been so overworked that it
has become worn out can now we revitalized and brought back into productive use. Biointensive works on some of the worst soils around and can be a valuable tool in regions of
the world debilitated by HIV/AIDS. If people living with HIV and their caregivers can grow
33
more and healthier food closer to their homes where they are needed to assist their loved
ones, then we will be that much closer to helping them improve the quality of their own
lives.
As yield levels increase, so too does the potential for real income generation
opportunities. Poverty reduction is often cited as one of the greatest needs in the fight
against HIV. With Bio-Intensive techniques, we can achieve both: poverty reduction through
income generation AND immune system building through an improved and varied diet.
Tools
Are special, expensive tools required? Absolutely not! Just as permaculture uses
locally available and appropriate plants in its guilds, bio-intensive gardening uses only locally
available tools and plants in its creation as well. Local hoes, and digging forks are all that is
required. How to Grow More Vegetables details the double dig method utilizing “western”
spades and digging forks but here in the land of the hoe, we need look no further. Fancy
tools only create one more barrier to adoption. Keep it simple; keep it local.
CONCLUSIONS
There are many things farmers can do to ensure food security for their families.
Applying fertilizer is one of them. While expensive, synthetic fertilizer is a quick and easy
way to significantly boost crop yields. This book encourages the continued use of fertilizer,
but it also emphasizes that there are many other things a farmer can do to achieve food
security. In other words, agriculture is not just planting seed and applying fertilizer.
To conclude, we introduce another Chitumbuka proverb: “Mukhuto nkha pingo” or
“To be full is a trap.” It is saying after you have eaten a big meal and you are full and
satisfied, beware! It’s a trap!! Tomorrow, that trap can just as easily snap back and hunger
can be at your door once again. This proverb is very forward-looking. It is suggesting that
we do the things we can do today to prevent being caught in the trap tomorrow.
As
farmers, let’s use ‘every tool in our shed’ to increase soil fertility for the future as well as for
the present.
We could say that synthetic fertilizer is a trap. Even though we might be managing to
stay full today from the great harvests that fertilizer makes possible, what about tomorrow?
Will the rising price of fertilizer be like a trap that snaps back on us leaving us hungry
tomorrow? What can we do as farmers, extension agents and researchers, students and
teachers to look toward the future and improve agriculture sustainably? If fertilizer becomes
expensive, can we generate more income to pay for it? Can we rely on alternative ways of
sustaining high yields on the same plots of land year after year?
The disadvantage of synthetic fertilizer is that its benefits last only one season. The
practices outlined in this book, however, will improve soil fertility far into the future; they are
not just for today or this rainy season. For example, practicing mini-composting (p. 20) or
34
early ridge preparation with burying green residues (p. 31) will not only add nutrients
for your next crop but will also adds organic matter that helps the farmer for many years to
come. When you plant leguminous agroforestry trees such as msangusangu or gulinga
(p. 12), they will cycle nutrients back to your topsoil for many years in the future. When you
plant a hedge bordering your field (p.28) or vetiver grass (p. 29) you not only prevent
soil erosion today but you will ensure that your children have fertile topsoil to till when
you’ve retired your hoe. Another advantage of the practices suggested in the book is that
they involve little, if any, financial inputs.
Knowledge and the willingness to experiment are all that are needed.
conclusion to this book, therefore, will remain undefined.
actions speak louder than words.
The real
You have read this book but
It is only after you have tried and applied the
principles that they begin to make sense. Do hoes cultivate food on their own? No, you are
the one making it work in the fields. Do teachings in a book magically make food appear?
No, but you can read about practices and then find the ones that work best for farmers in
your area. Hence, the conclusion here is up to you. And always remember: Healthy and
happy people eat healthy food which is grown in healthy soil. To build a strong community
of healthy people we must all work to build and nourish the soil within a healthy and
protected environment. The smiles below say it all!
35