Chitosan/kaolinite clay biocomposite as a sustainable and environmentally eco-friendly coating material for slow release NPK fertilizers: Effect on soil nutrients and tomato growth

Soil nutrient availability and non-biodegradation of some polymer-based slow-release fertilizers (SRFs) have a direct impact on crop production and soil ecological quality. Proper fertilization practices can lead to obviating adverse effects of over-fertilization on soil nutrients and, consequently, on crop yields. This work aims to assess the effect of a durable liner material based on biodegradable polymers on soil nutrient availability and tomato growth. For this purpose, Chitosan composite (CsGC) was adopted as a durable coating material, including clay as a reinforcing coating material. The influence of chitosan composite coating (CsGC) on the sustained nutrient release of coated NPK fertilizer (NPK/CsGC) was studied. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX) were used to examine the coated NPK granules. Results revealed that the proposed coating film improved the mechanical strength of the NPK fertilizer and enhanced water retention capacity of the soil. The agronomic investigation has also proved their outstanding potential to boost chlorophyll content, biomass, and tomato metabolism. Furthermore, the surface response study confirmed a strong correlation between tomato quality and representative soil nutrients. Therefore, kaolinite clay, as part of the coating system, can be an effective way to improve tomato quality and maintain soil nutrients during tomato ripening.