School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia; Science and Technology Division, Department of Environment and Science, GPO Box 2454, Brisbane, QLD 4001, Australia; Soil Science Division, Bangladesh Institute of Nuclear Agriculture, Mymensingh 2202, Bangladesh.
School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia; Science and Technology Division, Department of Environment and Science, GPO Box 2454, Brisbane, QLD 4001, Australia.
Sci Total Environ. 2022 Oct 20;844:157043. doi: 10.1016/j.scitotenv.2022.157043. Epub 2022 Jun 30.
Agriculture is the leading contributor to global nitrous oxide (NO) emissions, mostly from soils. We examined the non-target impacts of four pesticides on N transformations, N cycling genes and NO emissions from sugarcane-cropped soil. The pesticides, including a herbicide glyphosate (GLY), an insecticide imidacloprid (IMI), a fungicide methoxy ethyl mercuric chloride (MEMC) and a fumigant methyl isothiocyanate (MITC), were added to the soil and incubated in laboratory at 25 °C. The soil microcosms were maintained at two water contents, 55 % and 90 % water holding capacity (WHC), to simulate aerobic and partly anaerobic conditions, respectively. Half of the soil samples received an initial application of KNO and were then maintained at 90 % WHC for 38 d, whilst the other half received (NH)SO and were maintained at 55 % WHC for 28 d followed by 10 d at 90 % WHC to favour denitrification. Responses of individual functional genes involved in nitrification and denitrification to the pesticides and their relationships to NO emissions varied with time and soil water. Overall, MITC had pronounced repressive effects on AOA and AOB amoA gene abundances and gross nitrification. Under 55 % WHC during the initial 28 d, NO emissions were low for all treatments (≤62 μg N kg soil). However, under 90 % WHC (either during the first 28 d or the increase in water content from 55 to 90 % WHC after 28 d) the cumulative NO emissions increased markedly. Overall, under 90 % WHC the cumulative NO emissions were 19 (control) to 79-fold (MITC) higher than under 55% WHC; with the highest emissions observed in the MITC treatment (3140 μg N kg soil). This was associated with increases in gross nitrate consumption rates and abundances of denitrifying genes (nirK, nirS and qnorB). Therefore, to minimise NO emissions, MITC should not be applied to field under wet conditions favouring denitrification.
农业是全球一氧化二氮（NO）排放的主要贡献者，主要来自土壤。我们研究了四种农药对氮转化、氮循环基因和甘蔗种植土壤 NO 排放的非靶标影响。这些农药包括除草剂草甘膦（GLY）、杀虫剂吡虫啉（IMI）、杀菌剂甲氧基乙基氯化汞（MEMC）和熏蒸剂甲基异硫氰酸酯（MITC），被添加到土壤中，并在 25°C 的实验室中进行培养。土壤微宇宙保持在两种含水量下，分别为 55%和 90%的水分保持能力（WHC），以模拟有氧和部分厌氧条件。一半的土壤样本接受了初始的 KNO 应用，然后在 90%WHC 下保持 38 天，而另一半接受（NH）SO 并在 55%WHC 下保持 28 天，然后在 90%WHC 下保持 10 天，以有利于反硝化。硝化和反硝化过程中涉及的个别功能基因对农药的反应及其与 NO 排放的关系随时间和土壤水分而变化。总体而言，MITC 对 AOA 和 AOB amoA 基因丰度和总硝化作用有明显的抑制作用。在最初的 28 天内，55%WHC 下所有处理的 NO 排放都很低（≤62μg N kg 土壤）。然而，在 90%WHC 下（无论是在最初的 28 天内还是在 28 天后将含水量从 55%增加到 90%WHC 时），累积的 NO 排放显著增加。总体而言，在 90%WHC 下，累积的 NO 排放量比 55%WHC 高 19 倍（对照）至 79 倍（MITC）；在 MITC 处理中观察到的排放量最高（3140μg N kg 土壤）。这与硝酸还原消耗速率和反硝化基因（nirK、nirS 和 qnorB）丰度的增加有关。因此，为了最大限度地减少 NO 排放，MITC 不应在有利于反硝化的潮湿条件下施用于田间。
