Effect of planting density on yield and quality of later-sown winter wheat along Huaihe River

The area under later-sown winter wheat has since been increasing. To determine suitable planting density of later-sown winter wheat along the Huaihe River, we designed a split-plot field experiment including three later sowing dates (November 5, November 15 and November 25) and three planting densities (3×10⁶, 4.5×10⁶, and 6×10⁶ plants·hm^-2) for the 2013-2015 growing seasons. The yield and quality of winter wheat were investigated. The results showed that delay in sowing winter wheat shortened the growth stage of winter wheat, mainly affecting the length of vegetative period before jointing, but with little effect on the overall growth process. With delayed sowing date, dry matter accumulation at anthesis and maturity decreased, and translocation of dry matter in vegetative organs before anthesis along with the contribution of dry matter after anthesis decreased. At the same time, the contribution rate of dry matter after anthesis increased significantly. However, spike number, grain number per spike and thousand-grain weight all decreased, which caused significant reduction in yield. Moreover, protein, wet gluten contents and zeleny increased with delay of sowing date. Sowing date had more effect on dry matter accumulation and translocation in tiller stem spikes than on main stem spikes. Compared with November 5 sowing date, the November 25 sowing date decreased dry matter accumulation at anthesis, vegetative organ dry matter accumulation at maturity, grain dry weight, translocation of dry matter and its' contribution to grain of vegetative organs assimilate before anthesis respectively by 13.37%, 9.96%, 9.04%, 25.37% and 17.07% for main stem spikes; and respectively by 55.71%, 54.34%, 51.80%, 59.70% and 22.70% for tiller stem spikes. For the same sowing date, dry matter accumulation at anthesis and maturity increased with increasing planting density. Then translocation of dry matter in vegetative organ before anthesis decreased with increasing planting density. These conditions increased dry matter contribution to the related processes after anthesis. Also with increasing planting density, spike number increased, grain number per spike decreased, protein and wet gluten contents increased, but zeleny decreased. Compared with main stem spikes, planting density had more effect on dry matter accumulation and translocation of tiller stem spikes. Then compared with planting density of 3×10⁶ plants·hm^-2, 6×10⁶ plants·hm^-2 decreased grain weight per spike, grain number per spike and thousand-grain weight respectively by 17.90%, 13.60% and 4.76% in main stem spikes, and by 20.17%, 14.46% and 6.23% in tiller stem spikes. In conclusion, the rational increase in planting density increased yield and improved quality of later-sown winter wheat. Finally, our results showed that the best planting densities of later-sown winter wheat were 4.5×10⁶ and 6×10⁶ plants·hm^-2 for sowing dates of November 15 and November 25, respectively.