Xu Chao, Liu Weiping, Sheng G Daniel
Institute of Environmental Science, Zhejiang University, Hangzhou 310029, China.
Sci Total Environ. 2008 Mar 25;392(2-3):284-9. doi: 10.1016/j.scitotenv.2007.11.033.
Field burning of crop residue is a common post-harvest practice to dispose of these agricultural by-products and for land clearing. Burned crop residues may effectively adsorb pesticides and thus influence their bioavailability in agricultural soils. The adsorption of clomazone by a soil amended with a burned rice straw (BRS) was measured. The availability of clomazone to barnyardgrass in the soil in the absence and presence of BRS was tested. The BRS was 1000-20,000 times more effective than soil in sorbing clomazone. The sorption of clomazone by soil increased with increasing BRS amount in the soil. In a bioassay, the injury of barnyardgrass 9 days after planting decreased with increasing BRS amount in soil indicating the effect of BRS on clomazone availability. Residual analyses showed higher concentrations of clomazone in soils receiving higher rates of the herbicide than in soils with lower application rates suggesting the adsorptive role of BRS. At typical application rate of clomazone (0.3 microg g(-1)), BRS amounts of 0.02 wt.% and higher caused an appreciable reduction to a complete loss in clomazone availability. Calculations suggest that field burning of rice straw may result in sufficiently high amounts (>0.02 wt.%) of BRS, and hence contribute to often experienced loss of pesticide availability in agricultural soils. Our results may be extended to field situations where other crop residues and vegetation are burned. Alternative management of crop residues may improve the bioavailability of pesticides in agricultural soils.
田间焚烧作物秸秆是一种常见的收获后处理这些农业副产品和清理土地的做法。燃烧后的作物秸秆可能有效地吸附农药，从而影响其在农业土壤中的生物有效性。测定了添加了燃烧稻草（BRS）的土壤对广灭灵的吸附情况。测试了在有无BRS的情况下广灭灵在土壤中对稗草的有效性。BRS吸附广灭灵的效果比土壤高1000至20000倍。土壤对广灭灵的吸附随着土壤中BRS含量的增加而增加。在生物测定中，种植9天后稗草的伤害随着土壤中BRS含量的增加而降低，这表明BRS对广灭灵有效性的影响。残留分析表明，接受较高除草剂施用量的土壤中广灭灵的浓度高于施用率较低的土壤，这表明了BRS的吸附作用。在广灭灵的典型施用率（0.3μg g-1）下，BRS含量为0.02 wt.%及更高时，会导致广灭灵有效性显著降低直至完全丧失。计算表明，田间焚烧稻草可能会产生足够高含量（>0.02 wt.%）的BRS，从而导致农业土壤中农药有效性经常出现丧失的情况。我们的结果可能适用于其他作物秸秆和植被被焚烧的田间情况。对作物秸秆进行替代管理可能会提高农药在农业土壤中的生物有效性。
