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 .
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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.