Abstract
This study was aimed to attempt if we can fit a green manure legume in the gap between wheat harvest and rice plantation for sustainable rice (Oryza sativa) -wheat (Triticum aestivum) system. The effect of six green manure legumes viz. mungbean (Vigna radiata), cowpea (Vigna unguiculata), soybean (Glycine max), sesbania (Sesbania rostrata), pigeonpea (Cajanus cajan) and guar (Cyamopsis tetragonoloba) was assessed on rice yields and soil organic fertility in rice-wheat system for three consecutive years (2001/02-2003/04) at Agriculture Research Institute, Tarnab, Peshawar (Pakistan). The paddy and straw yields of rice were significantly increased by all green manure legumes during all the three years. However, on average, the greatest paddy and straw yields were recorded for cowpea and sesbania. The N uptake in rice was also significantly increased by legumes. However, the greatest N uptake occurred in the sesbania plot. Significantly positive effects of green manure legumes were also observed on soil organic matter, total N and mineral N relative to the fallow-based rice-wheat system. Our results suggest that the gap between wheat harvest and rice plantation can be effectively used to grow any green manure legume in general and sesbania or cowpea in particular in Khyber Pakhtunkhwa for sustainable rice-wheat system. Although this technology was tested in Peshawar valley, it has equal applications any where in the rice-wheat system.