Effect of soil amendments on persistence of hexaconazole and tebuconazole in soil and its residues in tomato

Abstract

A study was performed to determine the effect of soil amendments on persistence of hexaconazole and tebuconazole in soil and its residues in tomato. A typical black cotton soil was amended with FYM, gypsum, biocompost @ 5 tonnes/ha. The amended and unamended soils were treated with hexaconazole and tebuconazole at the rate of 2 mg/kg. Analytical protocol adopted for the analysis of residues of these fungicides from unamended and amended soil, and tomato fruits were validated. The linear range of hexaconazole was 0.05-1.0 mg/kg and for tebuconazole was 0.25-5.0 mg/kg on GC-ECD and GCMS-ITD, respectively. The extraction procedure for soil (amended and unamended) and tomato fruits were accurate and precise as the recovery and % RSD of hexaconazole and tebuconazole in amended and unamened clay soil and tomato fruits were in the range of 74.88 -112.98 and 1.56-16.0%, respectively. The LOD and LOQ of analytical method was less than 0.1 mg/kg for all the matrices analyzed. The persistence of hexaconazole was highest in soil amended with gypsum (DT50, 77 days) followed by biocompost (DT50, 68 days), FYM (DT50, 57 days) and without amendment (DT50, 45 days) soil. However, persistence of tebuconazole was highest in bio-compost (DT50, 69.31 days) amended soil followed by FYM (DT50, 66.01 days), gypsum (DT50, 43.87days) and unamended (DT50, 37.46 days) soil. The terminal residues of hexaconazole and tebuconazole in soil and tomato were correlated but impact of hexaconazole residues in soil on its terminal residues in tomato is quite high with respect to tebuconazole.