Environmentally friendly slow-release urea fertilizer based on modified chitosan membrane

The inefficient use of conventional fertilizers has prompted the exploration of slow-release fertilizer (SRF) systems to enhance plant nutrient delivery and uptake. This study investigates the potential of the chitosan (CS) membrane modified with succinic acid (SA) and calcium ions (Ca²⁺) as an effective SRF system. The CS/SA-U/Ca-coated membrane can extend the release period of urea, thereby optimizing fertilizer efficiency and promoting plant growth. The structural and chemical features of the CS/SA-U/Ca membrane were comprehensively analyzed. The modification with Ca²⁺ increased the membrane’s thickness, decreased its swelling degree, and resulted in a rougher, more porous surface, all of which contributed to a more controlled release of urea. Urea release profiles were evaluated in both water and soil, demonstrating that the CS/SA-U/Ca coating extended the release period to 20 days in water and over 30 days in soil. Quantitative UV–Vis spectrophotometry and qualitative assessments were used to measure the urea release and evaluate the impact of the SRF on vegetable plant growth. Experimental results demonstrated a significant enhancement in plant growth, with a 46 % increase in stem growth and a doubling of leaf count compared to control plants without the SRF membrane. These findings suggest that the CS/SA-U/Ca-coated SRF system holds promise for optimizing fertilizer use and promoting plant growth by providing a more controlled nutrient release.