Estimation of NPK requirements for rice production in diverse Chinese environments under optimal fertilization rates

Abstract Estimating crop nutrient requirements is essential for informing decisions of optimal nutrient management, but nutrient requirements often vary among climates and soil conditions. We assessed the nitrogen (N), phosphorus (P), and potassium (K) requirements of irrigated rice (Oryza sativa L.) in regions throughout China with different climates and soil chemical properties based on 3,896 measurements. We defined nutrient requirements as the aboveground uptake of N, P, and K required to produce 1 Mg of grain. The N and K requirements increased with increasing daily average temperature, solar radiation, N and K fertilizer rate, soil total N, Exchanged-K and organic matter content, total rainfall and potential evapotranspiration (ET) during the rice growing season and decreased with increasing growth duration, and harvest index (HI). In contrast, the P requirement mainly decreased with daily average temperature and solar radiation, increased with P fertilizer rate, soil Olsen-P. The estimated N, P, and K requirements of rice were 15.3, 6.0, and 19.9 kg Mg–1 grain in northern China and 21.0, 4.4, and 22.1 kg Mg–1 grain in southern China, respectively. The lower N and K requirements in northern China were attributed to lower nutrient concentrations and lower daily average temperature, solar radiation, total rainfall, ET, soil total N, and exchanged-K. The higher P requirement in northern China was mainly attributed to higher grain and straw P concentrations, which could be explained by the lower daily average temperature, solar radiation. Our results update the estimates of rice nutrient requirements based on direct field measurements, and these estimates help address disparities in Chinese nutrient budgets, develop and evaluate models and improve regional nutrient management to support research and policy.