Subsurface placement of controlled-release blended fertilizers mitigates ammonia volatilization by promoting nitrogen transformation in rice fields

Ammonia volatilization from rice fields is a major source of nitrogen loss following fertilizer application, but it can be mitigated by using controlled-release blended fertilizers, which synchronize nutrients release according to crop demand. Therefore, the current study was conducted for two consecutive rice-growing seasons; three levels of controlled-release blended fertilizers were compared with recommended fertilizers and simple blended fertilizers to evaluate their impact on ammonia volatilization, nitrogen transformation, and crop performance in rice fields. The results indicates that the application of controlled-release blended fertilizers significantly improved soil dynamics, enhances yield and yield components, increasing alkali nitrogen and ammonium concentration while reducing nitrate levels and ammonia volatilization compared to recommended fertilizers and simple blended fertilizers treatments. Furthermore, controlled-release blended fertilizers amendments boost nitrogen uptake and nitrogen recovery efficiency in rice plants by activating nitrogen metabolism enzymes, including nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate synthase, and upregulated the expression level of genes encoding nitrogen metabolism (NRT2.1, AMT1, GS1, and GOGAT1) which facilitated better nitrogen assimilation and utilization. Additionally, controlled-release blended fertilizers amendments stimulated soil enzyme activities, such as protease, cellulase, and dehydrogenase, in rice rhizosphere soil, improving nitrogen cycling and reducing nitrogen losses. During both years, controlled-release blended fertilizer treatment with 50 % reduced potash from potassium chloride source, decreased ammonia volatilization by 37 % and increased nitrogen uptake by 39 %, followed by treatment with 50 % reduced potash from potassium nitrate source, decreasing ammonia volatilization by 27 % and improving nitrogen uptake by 25 %. The treatment with 100 % potash from resin potassium nitrate source alleviated ammonia volatilization by 24 % and enhanced nitrogen uptake by 22 %, respectively. These findings suggest that controlled-release blended fertilizers achieves the optimal balance between nutrient availability and plant demand, improving nitrogen use efficiency. In summary, controlled-release blended fertilizers application to rice fields improves nitrogen use efficiency, reduce losses of nitrogen and enhances soil health, making rice cultivation more sustainable by decreasing ammonia volatilization and increasing rice yield.