Effect of Plow Pan on the Redistribution Dynamics of Water and Nutrient Transport in Soils

Plow pans are an essential part of the agricultural soil structure. By adjusting the soil bulk density and plow pan height, the water and nutrient transport are dynamically redistributed. Plow pans play a crucial role in promoting crop growth, increasing yields, and supporting sustainable land management. In this study, a column experiment was conducted to investigate the effects of plow pan height (10 cm and 15 cm) and bulk density (1.2, 1.4, and 1.6 g cm⁻3) on soil nutrient and water leaching under high-volume (HV) and low-volume (LV) fertilizer applications. The results reveal that the leachate volume decreased by 61.9% at a plow pan height of 10 cm and by 96.2% at a plow pan height of 15 cm when the bulk density was increased from 1.2 to 1.4 g cm⁻3 under HV conditions. There was no leachate when the plow pan bulk density was 1.6 g cm−3. The reserved concentration of alkali-hydrolyzable N in the plow pan soils was the highest when the plow pan had a bulk density of 1.4 g cm−3 and a height of 15 cm. However, when the plow pan height was 15 cm, the available P content in the plow pan soils decreased by 27.0% and 21.0% at bulk densities of 1.4 g cm⁻3 and 1.6 g cm⁻3, respectively, when compared with 1.2 g cm⁻3. Furthermore, the available P concentrations in the plow pan and subsoil layers decreased with an increase in the plow pan height. The available K concentrations in the topsoil decreased by 26.8% and 24.0% when the plow pan bulk density was increased from 1.2 to 1.4 g cm−3 at heights of 10 and 15 cm, respectively. Thus, the optimal plow pan height and bulk density are closely related to the types of soil nutrients. However, it is clear that excessively high bulk densities (e.g., 1.6 g cm−3) negatively impact soil properties. For different nutrient requirements, a bulk density of 1.2 or 1.4 g cm−3 can be chosen, with each providing suitable options based on the specific nutrient needs. This research offers practical insights into changes in nutrient adsorption and fixation in agricultural production associated with alterations in plow pan bulk density.