Intelligent Microsphere Soil Conditioner Based on Aminated Lignosulfonate and Thermoresponsive Polymer

In this research, a composite hydrogel microsphere material, SA/P(NVCL-ALS)-N-ZnO/A-Dol-urea (hereafter referred to as SA-PANZ), with dual responsiveness to temperature and pH, was developed by integrating aminated lignosulfonate sodium (ALS), poly(N-vinylcaprolactam) (PNVCL), nano zinc oxide (N-ZnO), and alkali-treated dolomite (A-Dol). The material exhibited excellent controlled-release performance, with a cumulative urea release rate of 67.22% at 40 °C and pH = 4. The Ritger-Peppas model fitted well with the release data, providing strong theoretical support for optimizing the microspheres. Compared to control groups, both the loading efficiency and encapsulation efficiency were significantly improved, achieving 38.50 and 12.83%, respectively. Water retention tests demonstrated that the microspheres maintained 39.92% of their moisture after 5 h, indicating an excellent water-holding capacity. Degradation experiments indicated a degradation rate of 60.14% under acidic conditions, demonstrating excellent biodegradability. Antibacterial assays revealed a clear inhibitory effect against Aspergillus niger, and plant cultivation experiments confirmed that the microspheres promoted pea growth under acidic and high-temperature stress. This research introduced a novel biodegradable microsphere-based soil conditioner with strong potential to improve nutrient use efficiency and soil quality in agricultural environments.