Residue and soil dissipation kinetics of chloroacetanilide herbicides on rice (Oryzae sativa L.) and assessing the impact on soil microbial parameters and enzyme activity

The present investigation determines the
persistence of herbicides like butachlor and pretila
chlor in Indian soil, and their impact on soil biologi
cal properties including microbial biomass carbon
(MBC), total microbial population numbers, and
enzyme activities. Butachlor was degraded faster in
autumn rice soil (t1/2 of 10–13 days) than in winter
rice soil (half-life of 16–18 days). The t1/2 of preti
lachlor in winter rice was 12–16 days. Regardless of the seasons under cultivation, no pesticide residue
was detected in rice at harvest. Herbicides induced an
initial decline (0–14th days after application) in MBC
(averages of 332.7–478.4 g g−1 dry soil in autumn
rice and 299.6–444.3 g g−1 dry soil in winter rice),
microbial populations (averages of 6.4 cfu g−1 in
autumn rice and 4.6 cfu g−1 in winter rice), and phos
phatase (averages of 242.6–269.3 μg p-nitrophenol

g−1 dry soil h−1 in autumn rice and 188.2–212.2 μg
p-nitrophenol g−1 dry soil h−1 in winter rice). The application of herbicides favored dehydrogenase
(averages of 123.1–156.7 g TPF g−1 dry soil in
autumn and 126.7–151.1 g TPF g−1 dry soil in winter)
and urease activities (averages of 279.0–340.4 g NH4

g−1 soil 2 h−1 in autumn and 226.7–296.5 g NH4 g−1
soil 2 h−1 in winter) in rice soil at 0–14th DAA. The
study suggests that applications of butachlor and pre
tilachlor at the rates of 1000 g ha−1 and 750 g ha−1,
respectively, to control the weeds in the transplanted
rice fields do not have any negative impact on the
harvested rice and associated soil environment.

本研究探明了丁草胺（butachlor）、丙草胺（pretilachlor）等除草剂在印度土壤中的持留特性，及其对土壤生物学特性的影响，涉及微生物量碳（microbial biomass carbon，MBC）、总微生物种群数量与酶活性。丁草胺在秋稻田土壤中的降解速率显著快于冬稻田土壤，其半衰期为10~13天，而冬稻田土壤中该除草剂的半衰期为16~18天。丙草胺在冬稻田土壤中的半衰期为12~16天。无论种植季型如何，收获期稻米中均未检出任何农药残留。除草剂施药后0~14天内，会引发微生物量碳（秋稻田土壤中均值为332.7~478.4 μg·g⁻¹干土，冬稻田土壤中均值为299.6~444.3 μg·g⁻¹干土）、微生物种群数量（秋稻田土壤中均值为6.4 菌落形成单位（colony-forming unit，cfu）·g⁻¹，冬稻田土壤中均值为4.6 cfu·g⁻¹）以及磷酸酶活性（秋稻田土壤中均值为242.6~269.3 μg对硝基苯酚·g⁻¹干土·h⁻¹，冬稻田土壤中均值为188.2~212.2 μg对硝基苯酚·g⁻¹干土·h⁻¹）的初始下降。而在施药后0~14天内，除草剂施用可提升稻田土壤中的脱氢酶活性（秋稻田土壤中均值为123.1~156.7 μg三苯基甲臜（TPF）·g⁻¹干土，冬稻田土壤中均值为126.7~151.1 μg TPF·g⁻¹干土）与脲酶活性（秋稻田土壤中均值为279.0~340.4 μg铵态氮·g⁻¹土壤·2h⁻¹，冬稻田土壤中均值为226.7~296.5 μg铵态氮·g⁻¹土壤·2h⁻¹）。本研究表明，在移栽稻田中分别以1000 g·ha⁻¹和750 g·ha⁻¹的剂量施用丁草胺与丙草胺以防控杂草，不会对收获的稻米及其关联的土壤环境产生任何负面影响。