An application strategy of combined controlled-release fertilizers can balance the yield and quality of soft wheat while meeting its nutrient requirements

The application of slow-controlled release fertilizer is a simple and labor-saving cultivation technology that can improve the yield and nitrogen use efficiency (NUE) of wheat, although research on the impact of a single application of controlled-release nitrogen (N) fertilizers with different release periods on wheat grain quality is still limited. In this study, urease inhibitor urea (AHA), sulfur-coated urea (SCU), a combination of SCU and AHA fertilizer (BSAF) and blended slow-controlled release fertilizer (BRNF) were used to investigate the effect of slow-controlled release fertilizers on the nutrient release, grain yield, NUE, and protein content of soft wheat. The goal was to determine the effect of a one-time application of controlled release fertilizer on wheat grain yield and protein content and its underlying mechanisms. The results showed that the different slow-controlled release fertilizer treatments had significantly different N release rates. AHA presented a fast release mode, while SCU and BSAF presented slow-release modes, and BRNF presented a controlled release mode. Compared with CK, BRNF increased grain yield and reduced the protein content of soft wheat, with an average increase of 6.73% in grain yield and a reduction of 1.85% in protein content. The higher N absorption of BRNF led to greater NUE, N agronomic efficiency (NAE) and N apparent recovery fraction (NRF). However, AHA, SCU and BSAF all showed the opposite trend. Compared with CK, BRNF improved post-anthesis dry matter accumulation (PDMA) and the contribution rate of dry matter accumulated post-anthesis to the grain (CDA), while reducing post-anthesis N accumulation (PNA) and the contribution rate of post-anthesis N accumulation to grain (CNA). The main reasons for the improvement in yield and reduction in protein content were related to the increases in PDMA and CDA, and the reductions in PNA and CNA, respectively. Therefore, BRNF is an effective agronomic strategy for promoting the coordination of grain yield and quality in soft wheat.