Objectives Tridimensional uniform sowing (TUS) is currently extended sowing method of winter wheat, the matching nitrogen fertilization has not yet been studied. The research compared the effect of topdressing time on the photosynthesis efficiency and grain yield of winter wheat, to provide reference for academic and efficient nitrogen fertilization specified for the tridimensional uniform sowing.
Methods Winter wheat field experiments with 3 factors split block design were conducted in the Experimental Farm of the Institute of Crop Sciences, Chinese Academy of Agricultural Sciences in Zhaoxian, Hebei Province, China in 2017–2018. The main block was tridimensional uniform sowing and sowing in drill; the subblock was four topdressing time of nitrogen at the initial jointing stage (T1), 10 days after jointing stage (T2), 20 days after the jointing stage (T3) and anthesis stage (T4); the sub-sub-block was two wheat cultivars of Hengguan-35 (HG35) and Han-6172 (H6172). During the anthesis stage, the SPAD values of flag leaves were measured using SPAD-502 Pluschlorophyll meter and the net photosynthetic rates were measured using LI-6400XT portable photosynthesizer. At maturity stage, the ear number per unit area, 1000-grain weight and the yield of wheat were investigated.
Results The highest panicle number and grain yield were achieved in T2 treatment for tridimensional uniform sowing of two wheat varieties, and the highest 1000-grain weight were T4 treatment for tridimensional uniform sowing. With the same sowing method, the highest plant height was in T1 for Hengguan-35, and in T2 for Han-6172. The spike length and spikelet number of the two wheat varieties reached the optimal value the nitrogen topdressing stage due to the different sowing method was different. In all the four nitrogen topdressing treatments, the flag leaf SPAD values and net photosynthetic rates of the tridimensional uniform sowing were greater than those of the drill sowing, and the net photosynthetic rate of flag leaf of nitrogen topdressing in T2 and T3 stages was significantly higher than that of nitrogen topdressing in T1 stage at 7th day and 21th day after anthesis. The SPAD values of flag leaves between the two wheat varieties were significantly different during the whole grain filling period, while the net photosynthetic rate of flag leaves was significantly different from the bloom day to the 7th day after flowering.
Conclusions Using tridimensional uniform sowing method, the properery nitrogen topdressing time is at the 10th day since jointing stage, which is beneficial to nutritional equilibrium in single plant, developing root system, forming superior tiller population, improving the number of panicles per unit area, and increasing yield finally.
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