Distribution of nutrients from controlled-release polymers in sandy soil

Abstract

Techniques such as fertilization can be used more frequently to achieve higher yield to crops. The problem of excessive use of fertilizers is related to losses of nutrients by leaching, contaminating water bodies. The adoption of controlled-release fertilizers may favor the reduction of losses and the total cost of fertilization, as the number of applications is reduced. This research aimed to study the dynamics of nutrients from polymer-coated fertilizers (KNO₃ controlled-release polymers) in sandy soil and analyze the spatial variation of soil solution storage at different depths when drip irrigation is adopted. Four soil boxes filled with Quartzipsamment and equipped with a mesh of 19 TDR probes were used to monitor soil moisture and electrical conductivity. Three soil boxes received the treatment consisting of 50 g of the controlled-release polymer and one soil box was used as a control. One liter of water was applied weekly through a drip irrigation system for ten weeks, followed by readings from the TDR probes to monitor the spatial variation of the soil solution storage in the soil profile. This monitoring allowed verifying that the release of nutrients happened slowly and gradually over the period without water retention by the material. The solution was displaced by advection (mass flow) and dispersion along with the irrigation water, which advanced more than the nutrients within the profile, reducing their leaching. Thus, controlled-release polymers maintained a slow and variable release over time.