Department of Agronomy, Himachal Pradesh Krishi Vishvavidyalaya, Palampur - 176 062, India.
Imazethapyr at 50, 100, 150 and 200 g/ha applied pre-plant incorporated, pre-emergence and early post-emergence was evaluated at Research Farm of Himachal Pradesh Krishi Vishvavidyalaya, Palampur. Increase in imazethapyr dose from 50 to 200 g/ha significantly reduced the weed dry matter and thus increased the seed yield of soybean. Application of imazethapyr significantly increased the nodule count compared to unweeded check but its effect on nodule dry weight was not significant. Nodule count increased significantly only upto 150 g/ha imazethapyr. The higher doses of imazethapyr though being statistically at par but increased the dry matter of nodules significantly over 50 g/ha. However, there was significant reduction in total number of soil bacteria with the increase in dose of imazethapyr from 50 to 200 g/ha. TIme of imazethapyr application did not influence nodule count, nodule dry matter and bacterial count significantly. The C2O evolution study indicates that imazethapyr was more toxic to anaerobic microflora than aerobic microflora. Imazethapyr 150 g/ha which was effective in controlling the weeds was comparatively safer to microbes in the soil than 200 g/ha under aerobic conditions.
