ghana climate change vulnerability and adaptation assessment

MAJOR CROPSMAIZEMaize is the most important food crop for smallholders, who obtain 20 percent of their caloric intake frommaize. Because maize also is used to meet their cash needs, about half of maize produced is marketed(Braimoh and Vlek 2006). The Northern Region once was Ghana’s leading producer of maize but yields havedeclined from an average yield in 1996 of >1200 kg/ha to less than 900 kg/ha in 2000 (Braimoh and Vlek2006). Soil quality is the most important factor in maize yields in northern Ghana; cropping systems areneeded that conserve soil organic matter (SOM) and minimize cultivation.Low soil organic matter and limited availability of plant nutrients, in particular phosphorus and nitrogen, aremajor bottlenecks to agricultural productivity in Ghana, which is further hampered in the Savanna Zone bysubstantial topsoil losses through wind and water erosion (Schlecht, Buerkert et al. 2006). Low soil organicmatter levels are due in part to “cut and carry” removals for livestock feed in the dry season. Residue burningto prepare fields for planting is another factor in low N inputs (Braimoh and Vlek 2006) and escapedagricultural fires are a problem throughout Ghana and is practically an annual event in parts of the savannazones.Braimoh and Vlek (2006) found that maize productivity in the Northern Region was limited by soil organiccarbon, low clay content (which affected moisture holding capacity), and low potential for chemical activity(ECEC, exchangeable cation exchange capacity). The average level of nitrogen additions was 8.3 kg/ha/yr,well below the optimum level of 100 kg/ha/yr; fertilizer additions decreased as costs rose relative to pricesfor maize. Fertilizer use was a major policy strategy in the 1960s and 1970s with the government providingsubsidies. After subsidies were removed in the structural adjustments of the 1980s, mineral fertilizer use bysmallholders declined rapidly (FAO 2003). In addition to price constraints, the lack of access to credit, poormarketing, and distribution of fertilizer affect farmers’ decisions (Braimoh and Vlek 2006).Planted legume fallows have been tested that improve soil fertility and crop yields but cover crops are notattractive to farmers unless there is an additional benefit, e.g., livestock feed. Even with these organic systems,added fertilizer phosphorus and possibly potassium additions are required to sustain or maximize yields(Braimoh and Vlek 2004). For example, legumes that fix atmospheric nitrogen need phosphorus inputs foroptimum production (Braimoh and Vlek 2006).GHANA CLIMATE CHANGE VULNERABILITY AND ADAPTATION ASSESSMENT 67