Productivity and light interception in upland rice - legume intercropping systems

The interact ion between upland rice and grain legumes (cowpea, groundnut , pigeon pea) in \nintercropping was investigated on a Vertisol over two years. Generally, intercropping was advantageous \nwi th a small reduction in rice yield and a substantial increase in yield of the legume. Pigeon \npea- r ice systems gave the highest intercropping advantage of 4 1 - 7 4 % in the first year. In the second \nyear, high intercropping advantages were recorded for cowpea and pigeon pea intercrops but \nthe indeterminate pigeon pea cv. Hy 3C reduced the expected rice yield by half. High irradiance \nearly in the rainy season increased the growth and yield of both rice and legumes compared to \nthe previous season, but intercrop rice was less competitive than Hy 3C. Canopy cover of rice was \nslowest compared to cowpea and pigeon pea, largely because of the erect leaf arrangement of rice. \nIntercropping invariably increased the amount of radiation intercepted due to faster canopy cover, \ni.e., spatial complementarity. It was concluded that determinate legumes are more appropriate for \nintercropping wi th upland rice.