Combined nitrogen and phosphorus management based on nitrate nitrogen threshold for balancing crop yield and soil nitrogen supply capacity

• Published in: Agriculture, ecosystems & environment Vol. 337; p. 108071
• Main Authors: Shi, Zujiao, Liu, Donghua, Luo, Wenhe, Hafeez, Muhammad Bilal, Li, Jun, Wen, Pengfei, Wang, Xiaoli
• Format: Journal Article
• Language: English
• Published: 01.10.2022
• Subjects: agricultural land; agriculture; environment; experimental design; fertilizer rates; nitrate nitrogen; nitrates; nitrogen; nitrogen fertilizers; phosphorus; phosphorus fertilizers; pollution; rhizosphere; soil; soil fertility; winter wheat; Zea mays
• ISSN: 0167-8809
• DOI: 10.1016/j.agee.2022.108071

An appropriate combined nitrogen (N) and phosphorus (P) fertilization strategy is essential for obtaining sustained higher grain yields while maintaining soil fertility. In this study, a long-term split-plot design farmland experiment (initiated in 2009) with five N fertilizer rates combined with four P fertilizer rates was established during 2016–2019 to determine an appropriate nitrate-N (NO₃-N) threshold in an intensive managed wheat–maize double cropping system. A fertilization strategy was then proposed based on the NO₃-N threshold to balance the crop yields and soil nitrogen supply capacity. The results showed that N fertilizer increased the accumulated NO₃-N, and the combined application of phosphate fertilizer with each N rate reduced the accumulated NO₃-N to different degrees. The residual soil NO₃-N reached a steady-state soil N pool balance after long-term application of N at 150–225 kg ha⁻¹ combined with P at 60–120 kg ha⁻¹. The residual NO₃-N threshold in the root zone (0–100 cm soil layer) was determined as about 100 kg ha⁻¹ at the crop harvest to maintain the N supply capacity and prevent leaching into the deep soil (>100 cm soil layer). The fertilization guidelines are 154 kg ha⁻¹ for N fertilizer and 106 kg ha⁻¹ for P fertilizer in the winter wheat season, and 162 kg ha⁻¹ for N fertilizer and 122 kg ha⁻¹ for P fertilizer in the summer maize growing season based on the NO₃-N safety threshold. The optimized fertilizer strategy reduced the fertilizer application rate by 67 kg N ha⁻¹ per year and the residual NO₃-N by 34.2 % in the deep soil, while only reducing the average yield by 3.1 % across the crops and years. These findings provide a basis for sustainably balancing grain yields and soil nitrogen supply capacity as well as preventing nitrate pollution of farmland.