除草剂对尿素氮在土壤中转化的影响

在实验室培养条件下研究除草剂草甘膦和丁草胺对尿素氮在菜地土壤中转化的影响。实验设对照、尿素、尿素＋草甘膦和尿素＋丁草胺4个处理,尿素氮用量为200 mg.kg-1（以干土计）,除草剂用量为w（有效成分）=10 mg.kg-1（以干土计）。结果表明,草甘膦和丁草胺对尿素氨化作用不产生抑制作用,甚至出现促进效果。2种除草剂在培养的前2 d均显著抑制硝化作用,但到第4天时显著促进硝化作用（P〈0.05）。草甘膦对反硝化作用表现显著的抑制作用（P〈0.05）,而丁草胺对反硝化作用有极显著的促进作用（P〈0.01）;丁草胺＋尿素、尿素、草甘膦＋尿素处理的反硝化损失量分别占施氮量的16.90%、6.34%和3.66%。可见,除草剂对土壤氮素转化有一定影响,但不同除草剂对氮素各个转化途径的影响有明显差异,不同除草剂品种间影响程度也不同。

Effects of herbicides on transformation of urea nitrogen in vegetable plantation soil

To assess the effects of herbicides on transformation of urea nitrogen in vegetable plantation soil,an incubation experiment was conducted under laboratory condition with 4 treatments including control,urea,urea＋glyphosate and urea＋butachlor,w（N）=200 mg.kg-1 by dry soil and w（active ingredient）=10 mg.kg-1 by dry soil were applied in urea and herbicide treatments respectively.The experimental results showed that glyphosate and butachlor had no negative impact on ammonification of urea or improved the ammonification activity;retarded the nitrifying rates of soil in 2 days in the beginning,but accelerated the rates at the 4th day significantly（P0.05）;Glyphosate inhibited denitrification（P0.05）,but butachlor promoted one（P0.01）.The nitrogen loss amounts by denitrification occupied 16.90%、6.34% and 3.66% of urea nitrogen applied in urea＋butachlor,urea and urea＋glyphosate treatments,respectively.In conclusion,herbicides markedly affected nitrogen transformation in soil,but different kind of herbicides appeared different impacts on processes of nitrogen transformation.