Gaynor J D, MacTavish D C, Labaj A B
Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, Harrow, Ontario.
Chemosphere. 1998 Jun;36(15):3199-210. doi: 10.1016/s0045-6535(98)00022-8.
Atrazine and metolachlor are extensively used in Ontario, Canada for control of broadleaf weeds and annual grasses in corn. Conservation tillage may alter the physical and biological environment of soil affecting herbicide dissipation. The rate of dissipation of these two herbicides in soil from conventional, ridge and no-tillage culture was followed. Herbicide dissipation was best described by first order reaction kinetics. Half life, the time for herbicide residues to dissipate to half their initial concentration, was unaffected by tillage. Half life for atrazine and metolachlor was similar and ranged from 31 to 66 d. The rate of dissipation decreased in dry years when soil moisture content was low. In a dry year, herbicide residues during the growing season were significantly greater on ridge tops than in the other tillage treatments. However, after harvest no differences in herbicide residues were detected among tillage treatments. Residues of atrazine (6 to 9% of applied) and metolachlor (4 to 6%) were detected in soil before planting a year after application. De-ethyl atrazine, the primary degradation product of atrazine, increased in concentration during the growing season with the greatest concentrations measured at harvest and in years when atrazine dissipated fastest. De-ethyl atrazine one year after application accounted for about 12% of the remaining triazine residue. These herbicide residues would not be phytotoxic to subsequent crops but are a potential source for leaching to ground and surface waters.
阿特拉津和异丙甲草胺在加拿大安大略省被广泛用于控制玉米田中的阔叶杂草和一年生禾本科杂草。保护性耕作可能会改变土壤的物理和生物环境，从而影响除草剂的消散。对这两种除草剂在传统耕作、垄作和免耕栽培土壤中的消散速率进行了跟踪研究。除草剂的消散情况用一级反应动力学来描述最为合适。半衰期，即除草剂残留消散至初始浓度一半所需的时间，不受耕作方式的影响。阿特拉津和异丙甲草胺的半衰期相似，在31至66天之间。在干旱年份，土壤湿度较低时，消散速率会下降。在干旱年份，生长季节垄顶的除草剂残留量显著高于其他耕作处理。然而，收获后各耕作处理间未检测到除草剂残留的差异。在施用一年后种植前，土壤中检测到阿特拉津残留量为施用量的6%至9%，异丙甲草胺残留量为4%至6%。阿特拉津的主要降解产物去乙基阿特拉津在生长季节浓度增加，在收获时以及阿特拉津消散最快的年份测得的浓度最高。施用一年后，去乙基阿特拉津约占剩余三嗪类残留量的12%。这些除草剂残留对后续作物不会产生植物毒性，但却是淋溶到地下水和地表水的潜在来源。
