The study looked at how different combinations of nitrogen, phosphorus, and potassium fertilizers affect rice grain yield in red paddy soil. They found that using a mix of N and P fertilizers had the biggest impact on increasing rice biomass, while K fertilizer had a smaller effect. Early rice crops benefited more from the fertilizers than later ones. Applying these fertilizers also changed the levels of organic matter and nutrients in the soil, with phosphorus increasing total and available phosphorus, and potassium increasing total and exchangeable potassium. However, too much potassium led to a decrease in rice biomass. Nitrogen fertilization lowered soil pH, while phosphorus fertilization slowed down the decrease in pH.