Water use efficiency and economic effects of a maize-legume intercropping system

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Nsongela, Shadreck Yona
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Maize-Legume intercropping systems are a common practice amongst small scale farmers in Zambia. However, the benefits of this practice are not fully understood due to inadequate information on the agronomic and economic effects of the system. There is need to find out more about the effects of maize-legume intercropping on water use efficiency, soil fertility, land use and labour needs. A study was conducted during the 1991 - 92 cropping season at the University of Zambia to establish the agronomic effects and economic benefits of a maizelegume intercrop. The specific objectives of the study were to investigate the effect of a maizelegume row intercropping system on water use efficiency by the crop components, and to establish the economic advantages of intercropping maize with legumes. Three intercropping experiments were conducted, and each consisted of a legume and maize. Soyabean (Glycine max L) variety Kaleya, common bean (Phaseolus vulgaris) variety Carioca and sunhemp(Clotalaria juncia) variety NIRS 3 were separately intercropped with maize (Zea mays L.)variety MM502. Each experimental unit was made up of four treatments namely maize monocrop, legume monocrop, maize-legume intercrop and bare (implanted plot). The treatments were arranged in a Randomized Complete Block Design with four replications. Soil moisture,biomass and grain yield were measured The study found that intercropping improved Water Use Efficiency (WUE). This improvement was attributed to high biomass yield due to increased planting densities. Intercropping was also found to be a more economic way of growing crops compared to monocropping because higher economic indices were obtained in intercrops than in monocrops. Land Equivalent Ratio (LER) and the Cropping Index (CI) were 1.31 and 2.00 respectively for the maize-soyabean intercropping system. The indices show that the intercrop required 31 % less land in producing yield equivalent to the sum of the two monocrops, and two different crops were simultaneously produced from the same piece of land. Similar results were observed in the maize-common bean intercropping system where the CI was 2.00. This study showed that although intercropping has been documented to offer both agronomic and economic benefits, these gains vary with factors such as prevailing agro-climatic conditions, farming techniques and cultural practices. There is thus need for continued research into intercropping systems under varying environmental conditions in order to develop technologies suitable for specific farming conditions.