Comparison of drip‐irrigated or injected allyl isothiocyanate against key soil‐borne pathogens and weeds

Abstract

BACKGROUNDAllyl isothiocyanate (AITC) is a soil biofumigant used for controlling soil‐borne pests that reduce the growth, quality, and yield of food crops. Its effectiveness against pathogens depends largely on its distribution in the soil, which is influenced mainly by the soil water content and application method. The distributions of AITC when injected with different moisture content or drip‐irrigated into soils were compared.RESULTSAITC injected at 50 g m−2 only diffused 10 cm deep in soil column with 5, 10 or 15% soil moisture content. The gas AITC peak concentration was 0.64 μg cm−3 at 5% moisture content. Diffusion was reduced when moisture content increased to more than 15%. The results of adsorption kinetics and release indicated that AITC's limited distribution was due to its low vapor pressure. AITC applied by drip irrigation at 7.5 g m−2 diffused 15 cm laterally and 30 cm deep where it reached concentrations of 0.022 μg cm−3 and 0.035 μg g−1, respectively. Some soil‐borne pathogens, nematodes and weed seeds closed to the point of AITC release were effectively controlled under drip irrigation, but efficacy decreased with increased distance. AITC applied by drip irrigation at 7.5 g m−2 and covered with PE film for 5 days provided a satisfactory efficacy against soil‐borne pathogens and weeds without any phytotoxicity.CONCLUSIONOur results indicated that AITC applied by drip irrigation was more effective than injection, which will guide applicators on methods to optimize the application of AITC for efficient control of key pests and weeds. © 2023 Society of Chemical Industry.

Encapsulated allyl isothiocyanate improves soil distribution, efficacy against soil‐borne pathogens and tomato yield

“…Our calculations assumed a field soil bulk density of 1.0 g cm −3 and an even distribution of AITC within 20 cm of the surface. EW was diluted 80‐fold with deionized water before being added to the flasks, as previously described 4 . Twenty microliters of TC ethyl acetate solutions with concentrations of 24.75, 49.50, 99, 198 and 396 g L −1 were added to the flasks for fumigation.…”

“…The method of extracting AITC from soil followed that previously described 25 . AITC gas and soil samples were detected using a gas chromatograph (GC Model 8890, Agilent Technologies Inc., USA) attached to a mass spectrometer (MS Model 5977B, Agilent Technologies) set in the select ion monitoring mode (94 and 79 m / z ) and interfaced with a headspace auto‐sampler (Model 7697A, Agilent Technologies) according to previous studies 4 . The retention time was 2.7 min and the AITC limit of quantitation (LOQ) in soil was 5 μg kg −1 and the LOQ of AITC gas was 0.001 μg cm −3 .…”

“…AITC was first registered in the United States in 2015 as a pre‐plant soil fumigant for application by shank injection or broadcast/flat fume. The emulsifiable concentrate in water (EW) formulation was first registered in China as a nematicide in 2018 applied by drip irrigation 4 . AITC, like many other plant‐derived products, is reported to have a low environmental impact 4 .…”

“…The emulsifiable concentrate in water (EW) formulation was first registered in China as a nematicide in 2018 applied by drip irrigation 4 . AITC, like many other plant‐derived products, is reported to have a low environmental impact 4 . The efficacy of a fumigant against pathogens depends on fumigant concentrations in soil remaining lethal to pathogens for sufficient time 5 .…”

“…Zhang et al . reported that AITC was evenly distributed within 10 cm of the surface and the concentration decreased as water content increased; drip irrigation improved AITC's distribution and its efficacy against soil‐borne pathogens 4 . However, applying AITC by drip irrigation may not be a viable option in areas where water is scarce or expensive 10,11 …”