Weed management in semi- dry rice intercropped with green manure crops

Abstract

An investigation was conducted during the kharif season of 2002 at Agricultural Research Station, Mannuthy to formulate weed management practices in semi-dry rice intercropped with green manure crops. Fourteen treatments were laid out in RBD with three replications involving combinations of two green manure crops (cowpea and horsegram) for in situ green manuring and six weed management treatments (butachlor, pendimethalin, pretilachlor, anilofos, handweeding and control) in addition to rice monocropping . . Results of the study revealed that an integrated strategy encompassing the application of pre-emergence herbicides and intercropping of green manure crops was successful from the point of view of weed management, organic manure addition and crop yield in semi-dry rice. Among the fourteen treatments tried, the highest yield of grain and straw was recorded by monocropped rice with hand weeding (T 13) which was on par with treatments intercropped with horsegram (Ts) and cowpea (T2), both receiving pendimethalin application. Intercropping with horsegram encouraged better growth of rice over cowpea. Averaging the grain yield of rice in intercropping treatments, it was found that concurrent growing of horse gram has significant superiority over cowpea. Comparing the unweeded plots with cowpea or horse gram intercropping and rice monocrop, it was observed that intercropping reduced the weed count to the extent of 42.8 to 56.8 per cent upto 60 DAS and cowpea was found superior in suppressing the population of weeds. The contribution of N, P and K by cowpea at the time of self decomposition was almost double that of horse gram, leading to an increased soil fertility status. Pendimethalin, pretilachlor and butachlor can be used safely both in rice + cowpea and rice + horsegram cropping systems and they favoured growth and yield of green manure crops and rice, apart from their superior weed control efficiency.