Release Behavior of Phosphorus from Bentonite Clay-Polymer Composites with Varying Cross-Linker Levels, and Neutralization Degree

Being of crucial significance for agrarian production, phosphorus and its forthcoming availability have drawn increasing attention over the last few years. Increasing phosphorus use efficiency without adverse effects to the environment is one of biggest challenges of agriculture. The use of clay-polymer composites loaded with phosphorus has provided solution to this problem. According to available data, for the first time in our laboratory, we have synthesized clay-polymer composites using modified bentonite, with different percentage of neutralization, as well as levels of cross-linking agent. Different types of clay, i.e., bentonite and organically modified bentonite, two levels (40 and 60%) of neutralization degree, and two levels (0.5 and 1%) of cross-linker were used to accomplish the target. The synthesized composites were subsequently loaded with diammonium phosphate fertilizer (14 grams diammonium phosphate fertilizer per unit weight of clay-polymer composites) and characterized via X-ray diffraction, Fourier transform infrared spectroscopy, transmission electronic microscopy, and scanning electron microscopy. Research findings indicated that highest cumulative phosphorus recovery (0.07 mg/kg soil in Alfisol and 0.26 mg/kg soil in Inceptisol) was recorded in the product synthesized from modified organo-clay in which neutralization degree was 60% and cross-linker level was 0.5%. Similarly, highest soil available phosphorus (7.2 mg/kg in Alfisol and 10.4 mg/kg in Inceptisol) was recorded in the same composite. Therefore, clay-polymer composites prepared from organo-clay can be considered as a promising carrier of phosphorus for enhancing its use efficiency.