Fertilizers boost crop production amongst smallholders in Zimbabwe

A dangerous myth thriving amongst some NGOs and environmentalists is that Africa can not feed itself because it is overpopulated, its agricultural potential has been completely tapped and it faces water shortages. The contrary is true: Africa has a staggering abundance of land and potential to produce rainfed crops, so much in fact that in theory it can feed the entire continent's rapidly growing population and have enough potential left to produce an amount of sustainably produced biofuels equal to the world's total current energy consumption (400EJ) (earlier post).

What Africa lacks is not land or water or agricultural potential (on the contrary), it is investments in land, in knowledge, in very basic farming inputs and in access to these inputs. Last year, the African Fertilizer Summit, which united some of the world's leading agronomists, made the point: if African farmers were to use the most simple of agricultural techniques (such as using micro-doses of fertilizers), the continent could double and, some estimate, even triple its current output at once. To those with an understanding of the realities of sub-Saharan African agriculture, this is stating the obvious.

People who are concerned with the environment should be staunch advocates of fertilizers: even very modest applications of the nuntrients increase crop productivity considerably and hence allow farmers to get more out of a plot of land. If African farmers - especially the millions of smallholders - are not encouraged or enabled to use such classic farming techniques, the socio-economic and environmental effects will be disastrous: land expansion, threats to pristine ecosystems, biodiversity loss, nutrient depletion, ever lower yields, more land expansion and ever deeper poverty. With deeper poverty comes higher fertility, more population pressure, increased food needs and more land expansion... This is an extremely dangerous cycle, but luckily, fertilizers are a major tool that can help turn this situation 180 degrees.

After four years of careful research, Dutch-sponsored agronomist Bongani Ncube demonstrated this simple idea, as it applies to the many smallholder farms in the semi-arid regions of her home country Zimbabwe. Neither water stress nor lack of crop rotations, but nitrogen availability was found to be the single factor that most limited farmers’ efforts to increase cereal yields. The application of micro-doses showed an increase in grain yields of not less than 100% during a normal rainy season.

With funds from the Netherlands Organisation for Scientific Research (NWO) Ncube studied smallholder farms in the southwest of Zimbabwe. She mapped resource flows and carried out field experiments. The Zimbabwean semi-arid regions are dry and farmers face food shortages every season. Yet not water management but the supply of fertilizer, especially nitrogen, was found to be the most important factor in increasing cereal yields. Zimbabwean farmers in the semi-arid regions hardly use fertilizer and manure at present. Chemical fertilizer is expensive and manure is not readily available. Moreover, little is known about the correct use of these nutrient sources in dry climates:
bioenergy :: biofuels :: energy :: sustainability :: water :: fertilizers :: agriculture :: yields :: food security :: poverty :: Africa ::

Nitrogen
The main issue when cultivating soil is the nitrogen balance. Continually cultivating the same crop disrupts this balance. With field experiments, Ncube demonstrated that a little bit of basal manure, and nitrogen fertilizer added as top dressing improved the maize yield by about one-hundred percent in a good rainy season and by up to fifty percent in drier seasons.

Crop rotation
Crop rotation is another option that could provide a lot of benefit according to Ncube. This is the cultivation of different crops alternately in successive years. Leguminous crops, for example, fix nitrogen. This nitrogen remains in the soil and is taken up during the next season by sorghum, a type of grain that grows well in dry areas. Ncube proved that grain legumes can be grown successfully under the semi-arid conditions in Zimbabwe. These legumes were able to leave enough nitrogen in the ground, which doubled yields of sorghum the following season compared to sorghum-sorghum rotations.

With a simulation model Ncube was once again able to show that nitrogen availability was more important in the rotation. These types of treatments often have a negative impact on water availability, yet here nitrogen was shown to be more important.

In short, Africa's agricultural potential is enormous, but socio-economic, and not environmental or ecological factors limit the concrete realisation of this potential. Policies must be focused on taking down the barriers that prevent African farmers from increasing their productivity: investments in extension services must be encouraged and the creation of fertiliser markets and access to those must be kickstarted. If these simple interventions succeed, the African continent could begin to hope to end the vicious cycle of low agricultural productivity that leads to increased environmental and population-related pressures on the continent's natural resources.

Image: A genuine smile: the application of micro-doses of NPK fertilizer doubled the yields on this woman's farm and consequently strengthened her family's income and food security. Courtesy: African Fertilizer Summit.

More information:
Netherlands Organisation for Scientific Research: Fertilizers help Zimbabwean farmers to increase crop yields - April 10, 2007.