Suneja, SunitaSaini, Babita2016-11-292016-11-292006http://krishikosh.egranth.ac.in/handle/1/88030In the present investigation, effect of long term use of clodinafop herbicide (used as permanent and rotational herbicide) on soil microbial populations and their activities in wheat field soil was studied. Soil samples collected before the application of herbicide were analyzed for soil chemical properties. Soil was of clay loam type. Soil pH ranged from 8.4-8.6 and EC ranged from 0.23-0.44 dSm-1. Organic carbon and total N were more in green manuring (GM) treatments than without green manuring (WGM) treatments. Total bacterial population was more in GM treatments than WGM treatments. At 15 days after the treatment (DAT) of herbicide, bacterial population was significantly less in rotational herbicide treated plot than weedy control under both GM and WGM conditions. At 30 & 60 DAT, bacterial count was more in permanent herbicide treated plots than rotational herbicide treated plots and weedy and weed free controls. Free living diazotrophs count was also more in GM treatments than WGM treatments. At 30 DAT, count was more in herbicide treated plots than weedy and weed free controls of GM condition while in WGM condition, there was not much difference in the population of different treatments. Ammonium oxidizer population increased after the application of herbicide in all the treatments upto 30 DAT. In GM condition, population was less in permanent herbicide treated plot at 15 DAT and in both (permanent and rotational) herbicide treated plots at 30 DAT as compared to weedy and weed free controls while in WGM condition, population was less only in rotational herbicide treated plot than weedy control at 15 DAT. Nitrite oxidizer population decreased after the application of herbicide in all the treatments. At 15 DAT, population was less in herbicide treated plots than weedy control in GM condition while in WGM condition, population was less only in rotational herbicide treated plot than weedy control. At 30 DAT, population increased and was significantly higher in permanent herbicide treated plots than weedy and weed free controls. Basal respiration, as indicated by carbon dioxide evolved, was slightly more in herbicide treated plots than weedy and weed free controls at 15 DAT and only in rotational herbicide treated plot at 30 DAT under both GM and WGM conditions. Later on, with the progress of time after application of herbicide, not much differences were observed in the basal respiration of different treatments under both GM and WGM conditions. Dehydrogenase activity was slightly higher in herbicide treated plots than weedy control of GM condition at 30 & 60 DAT while in WGM condition, activity was significantly less in herbicide treated plots than weedy control. Although herbicide treatments of GM condition had higher alkaline phosphatase activity than herbicide treatments of WGM condition but activity was less in herbicide treatments than weedy control at 15 & 30 DAT under GM condition while in WGM condition, enzyme activity in herbicide treated plots was not less than weedy control.enThesis