Clomazone Leaching Estimate in Soil Columns Using the Biological Method

ABSTRACT The chemical control of weed is a necessary practice in large-scale agriculture. However, when herbicides are used in the wrong way, they can remain into soil for long periods and/or be leached in its profile, and they may even contaminate groundwater. In this research, clomazone leaching in soil samples collected from different Brazilian regions was estimated by biological method. To do so, columns containing soils were used, and samples were collected every 5 cm. After preparing columns and applying a 1,500 g a.i. ha-1 clomazone dose, rain simulation was performed. Sorghum was used in order to detect the herbicide. More than 60% similarity was found for the studied variables; it was chosen to use only data referring to toxicity percentage. Clomazone did not cause reduction in sorghum cultivated in Organosol, thus indicating a strong herbicide sorption in this soil. Increased pH in Oxisol reduced leaching. More rainfall caused increased herbicide leaching in Oxisol (pH 5.1) and Quartzarenic Neosol. The highest leaching occurred in soils with lower pH and lower organic matter content. It is possible to conclude that, in soils with higher organic matter content, clomazone has lower risks of being leached.

摘要 规模化农业生产中，杂草化学防控是不可或缺的作业环节。然而，若除草剂使用不当，其可在土壤中长期残留，并在土壤剖面中发生淋溶，甚至污染地下水。本研究采用生物学方法，评估了巴西不同地区采集的土壤样品中异恶草酮（clomazone）的淋溶特性。试验采用土壤柱装置，每5 cm采集一次土壤样品；在装填土壤柱并施加1500 g有效成分/公顷的异恶草酮剂量后，开展模拟降雨处理。以高粱作为指示作物以检测除草剂残留。研究变量的相似性均超过60%，因此最终仅选取毒性百分比相关数据进行分析。有机土（Organosol）中种植的高粱未出现生长受抑现象，表明该土壤对该除草剂具有较强的吸附作用。氧化土（Oxisol）pH升高可降低除草剂淋溶风险。当降雨量增加时，pH为5.1的氧化土与石英砂质新成土（Quartzarenic Neosol）中的除草剂淋溶量均有所提升。pH值较低、有机质含量较少的土壤中，异恶草酮淋溶程度最高。综上可得出结论：有机质含量较高的土壤中，异恶草酮发生淋溶的风险更低。