Abstract
The interaction between upland rice and grain legumes (cowpea, groundnut, pigeon pea) in intercropping was investigated on a Vertisol over two years. Generally, intercropping was advantageous with a small reduction in rice yield and a substantial increase in yield of the legume. Pigeon pea-rice systems gave the highest intercropping advantage of 41-74% in the first year. In the second year, high intercropping advantages were recorded for cowpea and pigeon pea intercrops but the indeterminate pigeon pea cv. Hy3C reduced the expected rice yield by half. High irradiance early in the rainy season increased the growth and yield of both rice and legumes compared to the previous season, but intercrop rice was less competitive than Hy3C. Canopy cover of rice was slowest compared to cowpea and pigeon pea, largely because of the erect leaf arrangement of rice. Intercropping invariably increased the amount of radiation intercepted due to faster canopy cover, i.e., spatial complementarity. It was concluded that determinate legumes are more appropriate for intercropping with upland rice.
