Growing dry land crops on any scale by hand is hard work and yet most of Zambia’s maize is grown by small-scale farmers, the majority by hand. We have an almost perfect climate for growing maize and potential yields here can equal any in the world. Yet our national average maize yield is very low despite government extension and heavily subsidized fertilizer to the small-scale farmer. The underlying reasons for this are simple, our soil is being destroyed by bad agricultural practices. These ‘bad’ practices include: burning of residues, over-grazing of residues, excessive soil disturbance and minimal, if any use of organic soil amendments. All of these practices lead to depletion of the basis of any fertile soil –Organic Matter. Our goal with any cropping system is to increase organic matter as much as possible to build fertile and resilient soils for today, tomorrow and the future. Soils which are high in organic matter are: more able to hold onto nutrients, micro-organisms and moisture, hold a greater diversity of nutrients and micro-organisms, have a greater capacity to release chemically bound nutrients and are generally more disease and pest suppressive. My observation over more than 10 years of growing crops by hand is that all these are true. My neighbors who plough, burn or overgraze their land commonly receive drought stress up to three weeks before me, always have higher production costs and lower yields than me. My soil is improving every year whereas they complain of declining yields even with increased fertilizer application. The key is organic matter but how???
The traditional way to add organic matter to the soil is to return manure to the soil, preferably in the form of compost. The rise of fertilizer supplied cheaply all over the world has made it difficult to produce organic crops cost effectively for a few reasons:
1. because of the bulky nature of organic matter.
2. Because of the cost of production of compost.
3. Because the nutrients in organic matter are harder to quantify than in commercial fertilizer.
All of these are specifically true of the small scale farm in rural Africa where able bodied people are either moving to town or suffering from prevalent diseases.
The answers? Inter-cropped legumes, low labour/high nutrient compost and integrated animal husbandry. Here are some of the options we have identified in our environment.
Maize/dolichos lab-lab, a perrenial legune best suited to frost free areas where it grows throughout the dry season and gives excellent gound cover and organic matter production. Also an excellent fodder which is high in Lysine so also good for monogastric animals.
Maize/velvet bean. Can be used as a livestock feed at seed set or left to set seed and used in the modulated velvet bean system highlighted below.
In this system sunnhemp (crotalaria Juncea) or determinate cowpea (vinga spp) are grown between the row of maize spaced at 90cm at planting.
Then the maize is weeded in the row only and compost is added if needed.
Then the green manure is slashed or hoed and allowed to rot in situ as a 'top dressing'.
This trial gave us a 6 tonne per Ha equivelent with only 1 tonne compost per ha equivelent during weeding.
Here, red sunnhemp(crotalaria O.), was broadcast seeded at first weeding. As maize matures the sunnhemp starts flowering, good for forage or left in situ as a mulch.
Another example of red sunnhemp.
Here, Pigeon Pea (Cajanus Cajan) is planted at planting for maize or during the first weeding between the rows. This is an excellent option for farmers who need high quality forage into the dry season and those who have a market for the seed or like to eat it.
Next year I will try more options:
-Jack Bean, reputed to fix more than 300kg N per year, very drough tolerant and good in areas with heavily populated with stock as they apparently don't eat the foliage.
-Climbing beans as a food crop and ground cover plant.
-Silver-leaf desmodium, an excellent cover crop and forage often used as a repellent crop in the 'push/pull system developed in Kenya.
-Seven year bean, a prolific perrenial bean from Kenya, very good eating.
