It is impossible to study elements independently because their availability to crops is interdependent. Nitrogen- and phosphorus-based fertilization decisions are currently a research hotspot. Combining the relationship between higher grain yield and lower environmental impact to achieve higher sustainable fertilization management is a challenge in current field production. To address this challenge, this study developed a critical nutrient curve based on various fertilization to improve spring maize's fertilization management. Evaluating the relationship between total available nitrogen (TAN, mineral nitrogen, mineralized soil nitrogen, and residual soil nitrate-nitrogen before sowing) and grain yield, nitrogen use efficiency (NUE), and nitrogen leaching, suggestions on fertilization were put forward. Five different fertilizer rates (N 0 , N 1 , N 2 , N 3 , and N 4 represent N: P 2 O 5 application at 0-0, 120-60, 175-88, 230-115, and 285-143 kg ha -1 , respectively) were set for spring maize field experiment. A critical N curve and a critical P curve of spring maize were determined as %Nc = 2.64 × DM -0.25 and % Pc = 0.23 × DM -0.32 , with a linear relationship (Pc=-0.0124+0.0954 × Nc, R 2 =0.93) between Pc and Nc. A linear-plateau model can describe the relationship between maize relative grain yield and integrated N nutrition index (NNIi), where the maximum relative grain yield corresponded to 1.00 NNIi. Maize grain yield, biomass yield, and plant N uptake were closely related to the increase of TAN. Based on a linear-plateau model, the superior TAN value (TANmin, the minimum TAN was correlated with maximum relative grain yield) was 311 kg ha -1 . With an increase of TAN or NNIi, plant N use efficiency (NutE BY ) decreased first and then stabilized, from 188.6 kg -1 in N 0 treatment to 88.3 kg kg -1 in N 4 treatment. However, nitrogen leaching increased with NNIi or TAN, and nitrogen leaching reached 96-170 kg ha -1 under N 4 treatment. Under the TANmin value, NutE BY and N leaching were 98 kg kg -1 and 99 kg ha -1 , respectively. Therefore, Nc and NNIi values can provide helpful information on improving fertilization management of rainfed spring maize systems. Total available nitrogen is a method of nitrogen supply. Finding the optimal total available nitrogen can maximize grain yield, reduce chemical nitrogen input and reduce nitrogen loss. This study provided a calculation method for evaluating soil nitrogen supply capacity and a theoretical basis for optimizing fertilization
