Optimizing plant density and balancing NPK inputs in combination with innovative fertilizer product for sustainable maize production in North China Plain.

Excessive NPK inputs but low grain yield and high environmental impact are common in maize production in North China Plain (NCP). The objective of our study was to test whether a combined strategy of optimizing plant density, balancing NPK input, and innovating one-time fertilizer products could achieve a more sustainable maize production in NCP. Thus, a field experiment was conducted at Luanna County NCP with the treatments of unfertilized control (CK), farmer practice (FP, conventional plant density and NPK input), conventional one-time urea-based coated fertilizer (CF, optimized plant density and NPK input), and five newly designed innovative one-time NPK fertilizers of ammonium sulphate and urea synergy (IF, optimized plant density and NPK input), innovative fertilizer with various additives of urea inhibitors (IF+UI), double inhibitors (IF+DI), micro-organisms (IF+MI), and trace elements (IF+TE). The grain yield, nitrogen sustainability indicators (nitrogen use efficiency NUE, partial factor productivity of nitrogen PFPN, and nitrogen surplus), and cost-benefits analysis were measured and calculated over the maize growing season of 2020. Results had shown that on average the five innovative fertilizers (IF, IF+UI, IF+DI, IF+MI, and IF+TE) and CF that had optimized plant density and NPK input achieved 13.5%, 98.6%, 105.9%, 37.4% higher yield, PFPN, NUE, net-benefits as well as 67.5% lower N surplus compared with FP respectively. Notably, the innovative fertilizer with various effective additives (IF+UI, IF+DI, IF+MI, and IF+TE) which can be commonly found in the fertilizer market hadn’t resulted in an improvement in yield and NUE rather a greater cost and small net benefits in comparison to IF. In summary, our study highlighted the effectiveness of the combined strategy of optimized plant density, balancing NPK input, and innovative NPK products on sustainable maize production in NCP, however, the innovative fertilizers with effective additives should be properly selected for better economic benefits.