Conservative agriculture (CA) is claimed to be a panacea to issues of poor agricultural productivity and soil degradation in Sub-Saharan Africa (SSA). CA methods are said to increase and stabilize yields and reduce labor requirements, while improving soil fertility and reducing erosion. However, CAs will only work when a number of agronomic management practices are applied simultaneously. Although showing great promise in controlled experimental conditions with added inputs such as fertilizers and herbicides, CAs gain little actual foothold on African farms. The constraints identified by Giller et al. (2009) include: a low degree of mechanization within the smallholder system; lack of appropriate soil fertility management options; problems of weed control under no-till systems; lack of credit; lack of market for grain legumes; lack of appropriate technical information; competition for crop residues in mixed crop–livestock systems; and limited availability of household labor. Giller et al. determine that each bio-physical and socio-economic environment determines the degree of CA success. The review concludes that under present circumstance CAs can offer substantial benefits to some farmers, but are inappropriate for most resource-constrained farmers in SSA. — Anastasia Kostioukova
Giller, K., Witter, E., Corbeels, M., Tittonell, P., 2009. Conservation agriculture and smallholder farming in Africa: The heretics’ view. Field Crops Research 114, 23–34.
CA techniques are said to increase biological processes above and below ground leading to resource-efficient crop production. The three principles key to CAs are minimal or no mechanical soil disturbance, permanent organic soil cover, and diversified crop rotation. It is hard to assess CA practices, especially in demonstration programs, which include additional inputs such as fertilizers, herbicides, and improved seeds. Treating CA methods as indivisible concepts makes it difficult to discern the true source of crop growth stimulation, and evaluate benefits of each principle separately. Giller et al. determine that CA practices are most successful when configured to the environmental and social conditions of each growing region.
Important limitations exist under mixed African farming systems, which put constraints on adopting CAs. For example, in semi-arid areas where livestock are of great importance in income and risk management, crop residues are used as fodder instead of soil cover. Further, CAs can only gradually improve soil quality and crop yield. In the short-term, yield losses or no yield benefits are just as likely— a risk many resource constraint farmers are unwilling to take. Also in their initial years, CA systems have greater requirements for weed control. This creates demand in financial resources for herbicides or raising manual labor input for weeding. In addition, Giller et al. found that initial reduction in ploughing may cause mineral immobilization by affecting the rate of mineral absorption into soil. To offset yield reduction, farmers would need access to additional fertilizer until a new mineralization equilibrium is achieved. Adoptions of other CA principles, such as crop rotations are feasible only in regions where a ready cash market is available for famers to sell surpluses of grain legumes. In such cases, crops such as the groundnut (Arachis hypogaea) and cowpea (Vigna unguiculata) could improve soil fertility and be extremely beneficial for subsequent yields.
Switching from traditional farming methods to CA practices requires large amounts of initial input. Undertaking major transformation in crop and soil management proves overwhelming for most SSA smallholder farms. Additional burdens lie in remolding sensitive cultural rules and practices, such as traditional gender roles in agriculture. However, Giller et al. admit certain social benefits that may be bestowed upon farmers in light of the sheer complexity of CA systems compared to traditional practices. The authors offer evidence in support of positive social externalities associated with CA implementation, such as improvements in problem solving capacity as well as cooperation within SSA farming communities.