Tiller development affected by nitrogen fertilization in a high-yielding wheat production system

Quantitative understanding of how fertilizer N affects tiller development is essential for simultaneously achieving high yield and high N use efficiency in wheat (Triticum aestivum L.) production. A 3-yr field experiment was conducted on the North China Plain during 2015-2017, with winter wheat grown at five fertilizer N rates (0-300 kg ha(-1)). The highest grain yield (similar to 9 Mg ha(-1)) was obtained at the optimized N rate (on average 160 kg ha(-1), determined by subtracting the soil NO3- content from estimated N target values) and attributed to the high spike number, which was further contributed by the main stem (MS) and the fertile first tiller (T1). Greater N application than the optimized rate did not further increase grain yield but increased the biomass and N concentration of other tillers that were unproductive. The critical plant aboveground N concentrations (2.81% at stem elongation stage [Zadoks Growth Stage, GS 31] and 1.95% at anthesis (GS 64) and critical root-zone soil mineral N content (N-min) (74 kg ha(-1) at GS 31 and 129 kg ha(-1) at GS 64) for the attainable maximum stem number (1578 m(-2) at GS 31 and 944 m(-2) at GS 64) were quantified in this high-yielding system. The critical plant aboveground N concentrations for achieving the maximal biomass of stem were also established to be 2.72% at GS 31 and 1.53% at GS 64, respectively. At these critical levels, the maximal biomass of MS and T1 were obtained without increasing the growth of the other tillers that were unproductive. Our results showed that high yield of winter wheat can be achieved by increasing the number of productive stems and the biomass per productive stem through optimizing the root-zone N-min and plant N concentrations.