Rural population growth in Africa has resulted in smaller and smaller landholdings. Farmers in many areas of Tanzania are no longer able leave their fields fallow for several years, as they did in the past, to restore the soil’s fertility after a few years of growing crops.
Thus, overall soil fertility and crop yields are decreasing every year. Chemical fertilizers are difficult for most small farmers to afford and have to be subsidized to keep prices low. The small-scale farmers who are facing these challenges are very interested in cheap, reliable ways to improve the soil.
One of the conservation agriculture methods World Renew teaches relies on the extensive use of mulch to increase soil fertility and suppress weeds. Often, however, a scarcity of mulch limits the amount of land a farmer can manage to a relatively small plot.
Another agriculture method World Renew uses is green manure and cover crops. Along with three World Renew Tanzania partners, I recently attended a workshop sponsored by the Canadian FoodGrains Bank (CFGB) and facilitated by green manure/cover crop expert, Roland Bunch. Roland defined a green manure/cover crop as “a species of plant, usually a legume, whether it is a tree, a bush, a vine, a crawling plant, or an algae, which is planted by farmers to maintain or improve their soil fertility or control weeds, even when they have many other reasons for growing these plants.”
A natural forest is sustainable and maintains and restores fertility to the soil beneath it, while common farming methods deplete the soil’s fertility. By using green manure/cover crops, a farmer imitates the forest environment by ensuring that the soil is always covered, never plowed, and there is a maximum of foliage. The forest and green manure/cover crops both feed the soil by creating a layer of mulch. And as with the forest, the green manure/cover crop, once established, can continue year after year with very little cost or labor and no external inputs. Some green manure/cover crops can be planted along with food and cash crops, and others can be planted on fallow fields to dramatically reduce the time needed for the soil’s fertility to be restored.
Some green manure/cover crops provide food as well as fertilizer. One example is the longlived lablab bean. Once it has grown for five or six months, lablab becomes very drought resistant and can continue to produce seed and fodder for another four to six months—even without any rainfall.
Farmers in different areas of the country deal with different environmental and social conditions, including rainfall patterns, altitude and distance from the Equator, soil types, types of weeds found in their fields, types of land ownership, size of landholding, existing cropping patterns, and marketing opportunities. Thus, there is no “one size fits all” green manure/cover crop. We learned that there are hundreds of ways to use green manure/cover crops.
Working in groups and using the decision tree found in Roland’s book, Restoring the Soil, we were able to come up with a few options to share with farmers in each of the areas we serve.
Using the right green manure/cover crop method can enable the farmers we serve to produce good crops with increasing yields into the foreseeable future, even from poor soil. This can be done for almost no cost and with very little labor. We echo Roland’s enthusiasm from the start of his presentation, “No one in Africa should ever go hungry.” We are encouraged that by using these methods, no one in Africa will go hungry.
Thank you, Roland for your wisdom!
Jim Zylstra
Team Leader
World Renew Tanzania
