Effect of tillage and straw retention mode on seedling emergence and yield of spring wheat in the Hexi Irrigation Area

Seedling emergence rate and uniformity of crops determine their growth and yield performance, while straw retention and tillage mode play an important role on seedling emergence and growth of corps. To explore the responses of seedling emergence and yield of crops to straw retention and tillage practices, a field experiment was carried out in a typical oasis irrigation region, Wuwei, Gansu Province, in 2014 and 2015, to determine the effects of treatments of straw retention combined with tillage patterns on seedling emergence, yield, and yield components of spring wheat. The treatments included reduced tillage with 25 to 30 cm high straw standing (NTSS), reduced tillage with 25 to 30 cm long straw covering (NTS), tillage with 25 to 30 cm long straw incorporation (TS), and conventional tillage without straw retention (CT, the control). The results showed that, compared with CT, reduced tillage combined with straw retention treatments (NTSS, NTS) significantly decreased seedling emergence evenness of wheat, while TS increased seedling emergence evenness. NTSS and NTS increased spring wheat tiller number by 7.4% to 10.5% and 14.6% to 19.1%, effective spike rate of tiller by 13.5% to 20.1% and 33.0% to 34.7%, spike number by 7.5% to 9.3% and 10.3% to 11.2%, kernel number per spike by 15.7% to 16.1% and 18.5% to 22.6%, and thousand-kernel weight by 7.2% to 8.9% and 13.9% to 14.2%, compared with CT, respectively. There was no significant difference between TS and CT treatments in the above parameters. NTSS and NTS treatments had 16.6% to 17.4% and 18.6% to 21.4% higher grain yield than CT. NTS had the highest increasing effect on wheat grain yield, which was 10.3% to 11.0% higher under NTS than under TS. The increase of spike number and kernel number per spike was the main reason for yield increase under reduced tillage with straw retention treatments. However, emergence rate and uniformity had no significant impact on wheat production. Meanwhile, NTSS, NTS treatments were 9.4% to 10.7% and 10.5% to 11.1% greater in harvest index than CT treatment, indicating higher conversion rate of photoassimilates in wheat under the two treatments. Therefore, our results showed that reduced tillage in combination with 25 to 30 cm high straw retention was the feasible technology of wheat production in the oasis irrigation region.