Twice-split application of controlled-release nitrogen fertilizer met the nitrogen demand of winter wheat

As a new long-acting fertilizer, controlled-release nitrogen fertilizer (CRNF) has been shown to increase crop yield and improve nitrogen use efficiency (NUE) of fertilizer in many production systems. However, due to the limitation of nutrient release longevity of CRNF and the nitrogen demand characteristics of winter wheat (Triticum aestivum L.), further study is needed on the appropriate application technology of CRNF. In the present study, using polymer-coated urea (PCU) and sulfur-coated urea (SCU) as materials, the characteristics of nitrogen release from one-time or twice-split application of CRNF and its effect on the nitrogen uptake and growth of wheat were investigated in a two-year field experiment. The results indicated that nitrogen release from the twice-split application of PCU and SCU was synchronized with the nitrogen demand of wheat at different stages. Compared with urea multiple-split application (CK) and CRNF one-time application (PCU1 and SCU1), CRNF applied twice, at pre-sowing and re-greening (PCU2 and SCU2), maintained a high level of soil inorganic nitrogen after jointing, which met the second peak demand for nitrogen and improved the nitrogen uptake of wheat. Both PCU2 and SCU2 were found to be beneficial in delaying the senescence of leaves and the decline of photosynthetic performance after anthesis, which significantly increased the accumulation of post-anthesis dry matter and significantly affected the grain yield, with an increase of 9.96-15.11 % compared with multiple-split application of urea. PCU2 and SCU2 also improved NUE by 6.71-10.33 %. The results of this study demonstrate that CRNF applied twice was a good fertilization method for synchronizing nitrogen release from fertilizer and the nitrogen demand of wheat, thus improving wheat yield and NUE and decreasing the labor required for fertilizer application.