Abstract:

Intercropping is a traditional practice that has been in existence in developing countries for many years for a number of reasons. These include: Increased productivity per unit area; efficient use of limited resources such as land, labour, nutrients, light, time and water; reduction in pest damage due to diseases, insects and weeds; greater yield stability due to reduced risks; and economics of better use of land, labour, and capital or management of resources. A field experiment was carried out in East Ithaca (Cornell University, New York) in 1990 and 1991 growing seasons to determine if by altering proportions and population of beans and maize, a cropping system can be designed to produce more under limiting conditions. Three nitrogen levels of 0, 80 and 160 kg N/ha and five crop proportions of sole maize, sole beans, 75% maize + 25% beans, 50% maize + 50% beans and 25% maize + 75% beans were the treatments planted in a split-plot design. The bean cultivar used was Ruddy (red kidney, bush beans) and the maize cultivar was Pioneer 3925. Two bean rows were planted between two maize rows. Intercropping greatly increased dry matter accumulation per plant of beans and maize (gm/plant), and therefore, total dry matter in kg/ha. At the same time, nutrient uptake (kg/ha) was greatly improved by intercropping although nutrient concentrations in most instances were more in sole crops than intercrops. In 1990 and 1991 growing seasons, intercropping reduced incidence of Japanese and Mexican bean beetles compared to sole beans. Japanese and Mexican bean beetles decreased with decrease in bean proportions in the systems. Intercropped maize and beans were more efficient than sole crops in utilizing available resources with high land equivalent ratios (LER) values both under low and high maize population cropping systems. LER values decreased with increase in applied N fertilizer in both years. Total yield per hectare or combined yield of both beans and mai per hectare increased with increase in maize proportions while total income decreased with increase in maize proportions in both years. In 1990, intercrops produced higher income than sole crops. In 1991 under low maize population cropping system, sole beans produced the highest income although not significantly different from 75% bean proportion. Protein production was also affected by crop proportions and N fertilization. Intercropped beans produced a higher amount of protein both in 1990 and 1991 growing seasons than sole beans. Sole maize in 1990 produced more protein than intercropped maize, and in 1991 under both low and high maize population cropping systems, intercropped maize produced higher protein than sole maize.