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

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 (GA) 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 GA in saturated soils with different bulk densities (1.15-1.75 g/cm) and infiltration rates (0.2215-0.0017 mm/s) were analyzed using column experiments. The migration and distribution of GA in the soil with a depth of 50 cm were also investigated. The results indicated that GA could completely penetrate the soil with bulk densities less than 1.45 g/cm, and GA mass variation in the effluent was normally distributed. The maximum mass of GA in the effluent was calculated using the equation M(max) = 79.01 t (R = 0.9811), and 83.69-93.16 % mass of the added GA migrated downward in the soil. The analysis of the distribution of GA in the soil showed that GA 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 GA amounts in the soil were 75.07-96.47 % and 5-30 % of the added GA, respectively. Overall, the soil bulk density and irrigation volume determine what type of impact that GA may potentially have on the environment.