Phosphorus Availability and Adsorption Kinetics of Novel DAP Encapsulated Nano Clay Polymer Composites (NCPCs)

Abstract

A controlled environment experiment involving maize, combined with a study on soil incubation, was executed to evaluate the impact of nanoclay polymer composites (NCPCs) loaded with DAP through in-situ and ex-situ polymerization reactions on phosphorus (P) availability and its adsorption kinetics. This research was conducted during the kharif season of 2023, spanning from July to September, at the Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, B.H.U. Soil sub-samples were extracted and analysed at intervals of 5, 15, 30, 45, and 60 days post planting to assess P-availability. Concurrently, measurements were taken at 24, 72, 120, 168, and 240 hours to analyze P-adsorption kinetics. It was noted that the release of phosphorus was gradual in soil treated with encapsulated NCPC, particularly ex-situ NCPC, in contrast to conventional fertilizer. Moreover, phosphorus availability was found to be higher in NCPC-treated soil compared to conventional fertilizer, especially within the initial 45 days after sowing (DAS). The incubation experiment shed light on the dynamics of P-adsorption over a period of 240 hours. Greater adsorption was evident with 10 ppm solution in comparison to 20 ppm, while desorption was observed with 5 ppm solution initially. The peak adsorption occurred at 20 ppm, with levels stabilizing by the end of 240 hours. P-adsorption kinetics were more prominent in soil treated with phosphorus-loaded nanoclay polymer composite (NCPC) using the ex-situ method, as opposed to the in-situ method. Both first and second order kinetic models were found to be applicable for adsorption kinetics. Consequently, the experiment indicates that the ex-situ technique of fertilizer loading outperforms the in-situ method, possibly due to its capacity to enhance the polymerization of NCPC, leading to favorable results. The results imply that the integration of NCPC not only enhances crop growth but also contributes to the long-term sustainability of soil health through prolonged availability of nutrients.