Abstract:

【Objective】 To determine the effects of imazethapyr on nitrogenase and nitrate reductase activity in soybean and give evidence to assess the influence on nitrogen metabolism correctly after herbicide application. 【Method】 A field experiment was conducted to study the effects of imazethapyr on nitrogenase and nitrate reductase activity (NRA) after imazethapyr preemergence and postemergence applied. 【Result】 Nitrogenase was significantly reduced by imazethapyr in both treatments of preemergence and postemergence application. Although the reduction of nitrogenase activity was increased with time prolonging after imazethapyr preemergence, the nitrogenase activity was still reduced by 0.2186, 0.2198 and 0.2471 mmolC2H4?g-1?h-1 when imazethapyr was applied at 62.5, 125 and 250 ga.i.?hm-2 75 days after treatment. The reduction of nitrogenase activity was gradually decreased as time goes on after application of imazethapyr postemergence and 38 days after treatment, the nitrogenase activity was reduced by 0.1778 and 0.2177 mmolC2H4?g-1?h-1 at the application rates of 62.5 and 125 ga.i.?hm-2. Root NRA was significantly decreased after application of imazethapyr preemergence and postemergence and the reduced NRA gradually increased over time regardless imazethapyr application rate and application methods. Leaf NRA was strongly reduced within 30 days after application of imazethapyr postemergence. Leaf NRA was significantly reduced only at the application rate of 250 ga.i.?hm-2 75 days after preemergence application. 【Conclusion】 Nodule nitrogenase, root and leaf NRA were significantly reduced after application of imazethapyr preemergence and they have significant effect on inhibition of nitrogen metabolism of soybean.

Key words: soybean, imazethapyr, nodule nitrogenase, nitrate reductase