An evaluation of the performance of maize and cowpea in sole and intercropping systems at two savanna zones of Ghana: A simulation study.

The performance of maize and cowpea in sole and intercropping at two savanna zones in Ghana (Accra and Tamale) was evaluated using stochastic dominance and multi-criteria analysis techniques. The stochastic dominance analysis investigated the distribution of the simulated crop yields under a variety of farm management practices including the planting density, planting date and nitrogen fertiliser application rates over a twenty-year time period under rainfed conditions. Pair-wise comparison of the cumulative distribution functions obtained for the various management practices under each cropping system enabled the selection of the "best" combination of management practise for a given cropping system and site. Using the median gross margins of the best strategies to signify the long term economic viability of the cropping systems produced the following ranking for Accra: (i) under the natural soil fertility; sole maize < intercrop maize-cowpea < sole cowpea and (ii) with the introduction of moderate levels of nitrogen fertiliser (about 50 kg N ha(-1)); sole maize < sole cowpea < intercropping. Similar analysis at Tamale indicated that sole cowpea was the most preferred cropping system under the natural soil fertility condition whereas a modest application of nitrogen fertiliser increased the gross margins of sole maize and intercropping, the latter being the preferred choice. With the introduction of a relatively high level of nitrogen fertiliser (about 80 kg N ha(-1)), sole maize became the "best" cropping alternative The multi-criteria analysis considered the performance of the alternative cropping systems under both economic (gross margins) and sustainability factors such as soil cover, the quantity and quality of crop residue and the potential for nitrogen leaching. The results indicated that for a sustainable production, intercropping maize and cowpea together with a modest fertiliser application was generally the 'best' cropping system for both Accra and Tamale.