Long term effect of continuous or rotational use of herbicides and green manuring on weed flora, weed seed bank, soil properties and microbial population in rice-wheat sequence.

摘要

A long-term field experiment was initiated in kharif of 1999 to study the effect of green manuring and continuous or rotational use of herbicides on weed dynamics, sustainability and productivity of rice and wheat. The experiment is now running in 10th year. Green manuring reduced the population of grasses, BLW and sedges in rice effectively. In wheat, the density of grassy weed Phalaris minor in weedy check plots being lower under green manuring initially became higher than non-green manuring over the years. However, the population of BLW in weedy check plots under green manuring was at par with non-green manuring. But, under continuous use of grass killing herbicide clodinafop, population of BLW was lower under green manuring. There was high build up of Lathyrus aphaca population in non-green manured plots. The field data was also corroborated with weed seed bank studies in pots. There was slightly increasing trend in respect of organic carbon and available potassium under green manured plots. In general, the soil microbial population was more under green manuring in un-treated plots during initial crop stage. Grain yield of rice was improved by green manuring, whereas the effects on wheat yield were not that much prominent.