Department of Plant Sciences, University of California Davis, Salinas, CA, USA.
Pest Manag Sci. 2014 Mar;70(3):440-7. doi: 10.1002/ps.3586. Epub 2013 Jul 11.
The dissipation of pesticides in soil and the occurrence of accelerated degradation following repeated applications are well-known phenomena with many pesticides, but much less so with soil fumigants. The fate of various soil fumigants was studied in different agricultural soils following repeated applications of chloropicrin.
Fumigant dissipation reflected by Σconcentration × time (ΣC × T) and half-life values varied widely among the tested soils. Methyl iodide (MI) had the slowest dissipation rate compared with other fumigants in all tested soils. Elimination of biotic agents by soil sterilization prior to MI application did not affect MI concentration in Oxnard soil. Clay content and fumigant dose (ΣC × T values) of chloropicrin, 1,3-dichloropropene and MI were significantly correlated. No significant correlations were found between soil properties and ΣC × T values following metam sodium and methyl bromide (MBr) application.
The fate of the tested soil fumigants is highly dependent on and specific to the fumigant, previous fumigant application and soil type. This study suggests that biotic factors are more essential in the dissipation of metam sodium and MBr than abiotic factors. By contrast, MI dissipation from the tested soils is affected more by abiotic factors than by biotic activities.
许多农药在土壤中会发生消解，且重复施药后会加速降解，这是众所周知的现象，但土壤熏蒸剂则不然。氯代吡咯烷在不同农业土壤中重复施用后的各种土壤熏蒸剂的命运进行了研究。
以Σ浓度×时间（ΣC×T）和半衰期值来反映的熏蒸剂消解在测试土壤中差异很大。与其他熏蒸剂相比，在所有测试土壤中，碘甲烷（MI）的消解速度最慢。在施用 MI 之前通过土壤灭菌消除生物制剂不会影响 Oxnard 土壤中的 MI 浓度。氯代吡咯烷、1,3-二氯丙烯和 MI 的施药量（ΣC×T 值）与土壤的粘粒含量呈显著正相关。在施用甲酸钠和甲基溴（MBr）后，未发现土壤性质与 ΣC×T 值之间存在显著相关性。
所测试的土壤熏蒸剂的命运高度取决于熏蒸剂、先前的熏蒸剂施用和土壤类型。本研究表明，生物因素在甲酸钠和 MBr 的消解中比非生物因素更为重要。相比之下，测试土壤中 MI 的消解受生物因素的影响大于非生物因素。
