Effects of Granule Size Ranges on Dazomet Degradation and Its Persistence with Different Environmental Factors

Abstract

Pesticides are considered the most effective way to protect crops. However, irrational use has caused resources waste and environmental pollution. Dazomet (DZ) is a soil fumigant that has been used in many countries for decades, although it has caused occasional crop damage or insufficient control efficacy in some circumstances. In this study, the effects of DZ’s granule size and exposure to various environmental conditions on DZ degradation when used as a fumigant were demonstrated. The degradation rate of DZ was closely related to granule size. The half-life of larger DZ granules was longer than smaller granules with all studied environmental factors. The degradation rate decreased as the DZ usage (90–360 mg/kg) increased and different granule sizes showed the same variation trend. The half-life in each of the five granule size ranges tested decreased significantly as the temperature increased. DZ half-life decreased by 4.67–6.59 times as the temperature increased from 4 to 35 °C. Moreover, DZ usage and temperature affected the half-life of granules >400 and 300–400 μm in diameter significantly more than <100 μm granules. The half-life of all DZ granule sizes was reduced by 13.9–47.4% in alkaline compared to acidic conditions (pH from 9 to 5). Moreover, elevated temperatures could not only promote the production of methyl isothiocyanate (MITC) but accelerate its dissipation. The interactions between DZ granule size, dosage, temperature, and pH provide practical guidance on methods to improve DZ’s efficacy against pests and reduce the risk of phytotoxicity.