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

Abstract BACKGROUND Allyl 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. RESULTS AITC 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. CONCLUSION Our 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.