Effects of soil bulk density and corresponding soil infiltration rate on the migration and transformation of gibberellic acid.

Abstract

High intensity agricultural activities can lead to a decrease in soil fertility and an increase in soil bulk density, which may significantly impact the migration and transformation of pesticides in soil. As a new widely-used micro-toxic pesticide, gibberellic acid (GA₃) is more soluble and hydrophilic than most pesticides, which could readily migrate throughout the soil during water infiltration and impact groundwater quality. In this study, the leaching of GA₃ in saturated soils with different bulk densities (1.15-1.75 g/cm³) and infiltration rates (0.2215-0.0017 mm/s) were analyzed using column experiments. The migration and distribution of GA₃ in the soil with a depth of 50 cm were also investigated. The results indicated that GA₃ could completely penetrate the soil with bulk densities less than 1.45 g/cm³, and GA₃ mass variation in the effluent was normally distributed. The maximum mass of GA₃ in the effluent was calculated using the equation M_outlet(max) = 79.01 t^-0.97 (R² = 0.9811), and 83.69-93.16 % mass of the added GA₃ migrated downward in the soil. The analysis of the distribution of GA₃ in the soil showed that GA₃ accumulated in the upper soil layers with depths of 0-25 cm (the total depth of soil was 50 cm). In addition, the residual and hydrolyzed GA₃ amounts in the soil were 75.07-96.47 % and 5-30 % of the added GA₃, respectively. Overall, the soil bulk density and irrigation volume determine what type of impact that GA₃ may potentially have on the environment.