to increase agricultural productivity and address land degradation is managing soil fertility. Organic inputs such as manure and crop resi-
dues have been shown to raise crop yields and improve soil ecology.11 By increasing soil’s water- holding capacity and carbon content, organic inputs can help both adapt to and mitigate climate change. Organic soil fertility management can also reduce the amount of nitrogen fertilizer required. One study found that when leguminous trees were planted on maize plots in East and Southern Africa, the maize required up to 75 percent less synthetic nitrogen fertilizer.12 Reduced use of nitrogen fertil- izer could, in turn, reduce the water pollution that results when farmers apply too much fertilizer. In fact, research conducted in Sub-Saharan
Africa has shown that integrated soil fertility man- agement—the use of organic inputs, improved crop varieties, and judicious amounts of synthetic fertil- izers—is more profitable than the use of organic inputs or synthetic fertilizers alone. A recent study conducted in Kenya, Malawi, Mali, Nigeria, and Uganda showed that as farmers applied more organic inputs and fertilizers, both maize yields and soil carbon increased. Over a 30-year period, farm- ers who combined synthetic fertilizer and organic inputs experienced increasing or flat maize yields, whereas farmers who used organic inputs or syn- thetic fertilizer alone experienced falling yields. Further analysis showed that by using integrated soil fertility management, farmers could increase the financial return to applying one kilogram of nitro- gen by an average of about 60 percent, compared with use of fertilizer alone.13 Countries that allocate
large shares of their agricultural budgets to fertil- izer subsidies may be able to increase the returns to public spending by giving subsidies on the condi- tion that the beneficiary adopts an easily verifiable organic input practice such as agroforestry.14 Despite its win-win-win advantage of greater
yield, profit, and environmental services, adoption of integrated soil fertility management is low—oſten lower than the use of synthetic fertilizer or organic inputs alone (Table 1). Tere may be several reasons for this low adoption rate. Farmers are less likely to adopt this practice when they have litle household capital, are far from roads and markets, and have no livestock to produce manure and help transport bulky inputs. According to preliminary research results, women farmers are more likely to use organic inputs and less likely to use synthetic fertil- izer than men, but greater endowments of finan- cial and physical assets increase their propensity to adopt integrated soil fertility management practices. Te capacity of agricultural extension services
in Sub-Saharan Africa to provide integrated soil fertility management technologies is low. Only a small share of agricultural extension agents in Nigeria and Uganda, for example, were shown to provide advisory services on organic inputs. Most of their agricultural advisory services focused on improved seeds, fertilizers, and pesticides.15
CONCLUSION
In 2011 two United Nations bodies adopted ambitious goals for halting land degradation and achieving sustainable development. These
TABLE 1 Adoption of integrated soil fertility management in six Sub-Saharan African countries Soil inputs
Organic inputs and synthetic fertilizer Organic inputs alone Synthetic fertilizer alone
KENYA 19.6 29.4 10.5
MALAWI 14.7 18.6 70.8
Farmers' rate of adoption (%) MALI
17.7 38.7 16.3
NIGER 0.0 1.0 0.1
NIGERIA 7.5
12.1 45.3
UGANDA 2.0
11.9 6.1
Sources: Kenya, Niger, Nigeria, and Uganda: Compiled from E. Nkonya, F. Place, J. Pender, M. Mwanjololo, A. Okhimamhe, E. Kato, S. Crespo, J. Ndjeunga, and S. Traore, Climate Risk Management through Sustainable Land Management in Sub-Saharan Africa, IFPRI Discussion Paper 01126 (Washington, DC: International Food Policy Research Institute, 2011); Mali: Government of Mali, Recensement general de l’agriculture, Campagne agricole 2004–2005; Malawi: Ministry of Agriculture and Food Security household survey 2008. Note: In this case, organic inputs consist of ani- mal manure. Farmers are considered to be using integrated soil fertility management when they adopt both organic inputs and synthetic fertilizer (all farmers had already adopted improved crop varieties).
66 LAND UNDER PRESSURE
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