The Gacheru Self-Help Group, a farmers’ group in central Kenya, has
benefited by using a fertilizer made from local weeds. According to the
farmers, the organic fertilizer solution works well and is far cheaper
than inorganic fertilizers. The process for making the solution was
developed by the Kenya Agricultural Research Institute and involves
extracting juice from two local weeds, Desmodium and Tithonia. These
weeds are high in nitrogen, which boosts crop yields, says farm manager
Samuel Mugo. "They fight all manner of destructive weeds and give us
high yields from our farms." The process is simple. The farmers thresh
the weeds, then mix them with water in a drum. The solution is then
ready to use.
Zambian farmers use termite soil to improve soil fertility: Zambian
farmers traditionally used soil from termite mounds as a fertilizer. But
when inorganic fertilizers became available at subsidized prices, this
practice declined in popularity. When the subsidies were removed, many
farmers resumed the practice.
A suitable termite mound is chosen and cleared of vegetation. Soil from
the top of the mound is removed, but the base is left intact so that the
colony is not destroyed. The soil is transported to the field and,
before the rains begin, farmers work it into the topsoil with ploughs,
hoes or shovels. Where farmers practice conservation farming, the soil
is placed in planting pits.
The termite soil is applied once every three years. Maize harvests were
33 percent higher in fields with termite soil than in fields where
inorganic fertilizers were used. Termite mound soils have lots of clay,
which improves water storage. In southern Zambia, soils are normally
poor at holding water, so using termite soil helps hold more water and
improve crop yields. Termite soils also have high levels of calcium,
phosphorus and organic matter, which all contribute to better crop
yields and health.
Other useful practices for improving soil fertility include:
* Composting: Making compost involves combining fresh “green” plant
materials which contain lots of nitrogen (for example, fresh leaves and
kitchen food waste) with older “brown” materials such as crop residues
which are high in carbon. These materials are mixed and then broken down
– normally in a compost pit or compost pile – through aerobic
decomposition (decomposition in the presence of oxygen) into a rich
black soil. The decomposition is performed by micro-organisms, mostly
bacteria, but also yeasts and fungi. The process of composting is simple
and can be practiced by individuals in their homes, farmers on their
land, and by people living in cities. There are many ways to create and
use compost. To learn about various methods, see Farm Radio
International scripts on compost at
http://www.farmradio.org/english/radio-scripts/fertilization.asp.
* Animal manure: Animal dung contributes to soil fertility by
adding organic matter and nutrients, especially nitrogen. Livestock
manure often includes plant materials such as the straw used for animal
bedding. Livestock bedding is also useful because it has often absorbed
animal dung and urine.
* Using rock phosphates: These are mined rocks which contain
phosphate, and which are used to provide the mineral phosphorus, the P
in N-P-K. Natural deposits of rock phosphates are found in Senegal,
South Africa, Mali, Tanzania, Nigeria, Niger, and some other African
countries. See further resources at
http://farmradio.org/english/radio-scripts/74-8script_en.asp and
http://www.uoguelph.ca/~geology/rocks_for_crops/ * Agroforestry: Growing trees and shrubs together with crops
reduces the loss of soil nutrients. Because trees and bushes usually
have highly developed root systems, they can absorb and store many
nutrients which are unavailable to crops with shallow root systems. In
this way, trees and shrubs keep nutrients from being leached during
periods when no other crops are being cultivated. After the leaves or
cuttings fall to the ground, the nutrients once again become available
to the crops as the leaves and cuttings decompose. Trees and shrubs can
also form hedges that protect crops and soil from wind and from heavy
rains which runoff over the surface of the soil. For example, in West
Africa, Acacia species increase soil fertility by providing organic
matter in its leaves, fixing nitrogen in the soil, capturing nutrients
with its extensive root system, and shading cattle in the dry season
(the cow dung enhances soil fertility).