Hansen N C, Moncrief J F, Gupta S C, Capel P D, Olness A E
WCROC, Univ. of Minnesota, Morris 56267, USA.
J Environ Qual. 2001 Nov-Dec;30(6):2120-6. doi: 10.2134/jeq2001.2120.
Herbicides transported to surface waters by agricultural runoff are partitioned between solution and solid phases. Conservation tillage that reduces upland erosion will also reduce transport of herbicides associated with the solid phase. However, transport of many herbicides occurs predominantly in solution. Conservation tillage practices may or may not reduce transport of solution-phase herbicides, as this depends on the runoff volume. Reducing herbicide application rate is another approach to minimize off-site transport. Herbicide banding can reduce herbicide application rates and costs by one-half or more. Our objective was to compare herbicide losses in runoff from different tillage practices and with band- or broadcast-applied herbicides. The herbicides alachlor [2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide] and cyanazine [2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropionitrile] were broadcast- or band-applied to plots managed in a moldboard plow, chisel plow, or ridge till system. Herbicide concentration in runoff was largest for the first runoff event occurring after application and then decreased in subsequent events proportional to the cumulative rain since the herbicide application. When herbicides were broadcast-applied, losses of alachlor and cyanazine in runoff followed the order: moldboard plow > chisel plow > ridge till. Conservation tillage systems reduced runoff loss of herbicides by reducing runoff volume and not the herbicide concentration in runoff. Herbicide banding reduced the concentration and loss of herbicides in runoff compared with the broadcast application. Herbicide losses in the water phase averaged 88 and 97% of the total loss for alachlor and cyanazine, respectively. Cyanazine was more persistent than alachlor in the soil.
通过农业径流进入地表水的除草剂会在溶液相和固相之间分配。减少旱地侵蚀的保护性耕作也会减少与固相相关的除草剂的迁移。然而，许多除草剂主要以溶液形式迁移。保护性耕作措施可能会也可能不会减少溶液相除草剂的迁移，因为这取决于径流量。降低除草剂施用量是减少场外迁移的另一种方法。除草剂条施可以将除草剂施用量和成本降低一半或更多。我们的目标是比较不同耕作方式以及条施或撒施除草剂情况下径流中除草剂的损失情况。将除草剂甲草胺[2-氯-2',6'-二乙基-N-(甲氧基甲基)乙酰苯胺]和氰草津[2-[[4-氯-6-(乙氨基)-1,3,5-三嗪-2-基]氨基]-2-甲基丙腈]撒施或条施到用铧式犁、凿式犁或垄作系统管理的地块上。施用后第一次径流事件中径流中的除草剂浓度最高，随后的事件中其浓度会随着自除草剂施用以来的累计降雨量成比例下降。当除草剂采用撒施时，甲草胺和氰草津在径流中的损失顺序为：铧式犁>凿式犁>垄作。保护性耕作系统通过减少径流量而非径流中除草剂的浓度来降低除草剂的径流损失。与撒施相比，除草剂条施降低了径流中除草剂的浓度和损失。甲草胺和氰草津在水相中的损失分别平均占总损失的88%和97%。氰草津在土壤中的持久性比甲草胺更强。
