Effects of Phosphate Application Rate on Grain Yield and Nutrition Use of Summer Maize under the Coastal Saline-Alkali Land

Saline-alkali soil is a major threat to global food security. Phosphorus (P) fertilizer is essential for crop growth and yield production. Nevertheless, the optimal phosphate fertilizer application rates for summer maize under coastal saline-alkali soil are still unclear. A field experiment with five phosphate application rates (0, 45, 90, 135, and 180 kg ha-1, referred to as T1, T2, T3, T4, and T5, respectively) was conducted during the 2018-2020 summer maize seasons study the effects of phosphate rates on the grain yield, biomass, and nitrogen (N), P and potassium (K) accumulation, and N, P, and K physiological efficiency (denoted as NPE, PPE and KPE, respectively). Results showed that P application notably improved maize grain and biomass yield, the total uptake of N, P, K, and NPE and KPE across three seasons. As the P addition increased to 135 kg ha-1, the grain yield achieved a maximum of 7168.4 kg ha-1, with an average NPE of 2.15 kg kg-1, PPE of 0.19 kg kg-1, and KPE of 1.49 kg kg-1. However, PPE continuously decreased with the input of phosphate. P application rates exceeding 135 kg ha-1 were not considered effective due to a decline in grain yield, nutrient uptake, and NPE. Furthermore, the effect of the planting season was significant on the total uptake of N and K, and the use efficiency of N, P, and K. TOPSIS revealed that a phosphate application rate of 90-135 kg ka-1 was the optimal pattern for maize production. These results may give a theoretical basis for the phosphate management of maize production in saline-alkali soil.