Effects of sowing date and seeding rate on soil water consumption and plant nitrogen translocation in dryland wheat

Abstract

To tackle the issue of rainfall delay during dryland wheat sowing season and further examine the effects of seeding rate on water use and yield formation, a field experiment was conducted at Wenxi Experimental Station, Shanxi Province between 2015 and 2017. We used two sowing dates, i.e. September 20 and October 10 as early (EB) and late (LB) sowing in main plots, and each with three seeding rates as 67.5 (LD), 90 (MD) and 112.5(HD) kg·hm-2. The results showed that compared with LB, EB increased total soil water consumption by 11-22 mm over the entire growing season. With the increases of seeding density, total soil water consumption increased by 2-20 mm. Soil water consumption before anthesis tended to increase for LB, while there was a significant increase of soil water consumption after anthesis for EB. Compared with LB, the pre-anthesis nitrogen translocation and post-anthesis nitrogen accumulation amount in EB were increased under LD and MD, but decreased under HD. For EB, the pre-anthesis nitrogen translocation amount and post-anthesis nitrogen accumulation amount were highest at LD. Under LB, the pre-anthesis nitrogen translocation amount and post-anthesis nitrogen accumulation amount were greatest at high sowing density. EB significantly increased grain yield by 163-996 kg·hm-2 than LB. EB significantly increased grain yield and water use efficiency by 5%-26% and 2%-21% compared with LB, respectively. The nitrogen absorption efficiency and harvest index were 3%-36% and 11% higher under LB than that under EB. As for seeding rate, a low level tended to gain higher grain yield, water use efficiency, nitrogen uptake efficiency and nitrogen harvest index under EB, whereas a high level tended to gain higher values of grain yield, water use efficiency, nitrogen uptake efficiency and nitrogen harvest index under LB. In addition, the pre-anthesis nitrogen translocation was closely related with 100-200 cm soil water consumption before anthesis, especially for stem + sheath, glume + spike nitrogen translocation. The post-anthesis nitrogen accumulation was significantly correlated with 100-300 cm soil water consumption after anthesis. In conclusion, early sowing with a seeding rate of 67.5 kg·hm-2 and late sowing with a seeding rate of 112.5 kg·hm-2 could be promising options to boost dryland wheat production.