Crop rotation, factor productivity, cropping system, weed dynamics

A field experiment was initiated in 2000-01 at Varanasi Centre of AICRP on Cropping Systems to study the effect of diversification of rice-wheat system on weed dynamics in rice. The results of 2002-03 and 2003-04 i. e. 3rd and 4th year of study revealed that diversification of rice-wheat system through inclusion of greengram in summer, though remained at par to sequences involving summer cowpea for fodder or Sesbania for green manuring, resulted in significantly lowest population of grasses and sedges in 2003-04 and weed dry matter production in both the years. However, the different cropping sequences failed to affect broadleaf weeds population. Similarly, sequences having grain/fodder legume or Sesbania for green manuring produced higher grain and straw yield than rice-wheat sequence. Nevertheless, the differences were significant only in 2003-04 during which rice-wheat-Sesbania though remained at par with rice-wheat-greengram, rice-lentil+mustard (3 : 1)-cowpea, rice-maize+pea (1 : 1)-cowpea and rice-potato-greengram produced significantly higher grain yield than other sequences and registered 14.5% higher grain yield than rice-wheat sequence.