Effects of long-term no-tillage with crop stubbles on yield and stability of spring wheat in Hexi Oasis Irrigated Areas

This study aims to explore the tillage practices for the efficient and sustainable production of spring wheat in Hexi Oasis Irrigated Areas. A long-term no-tillage with stubble field experiment was conducted in the Wuwei area (38°07′N, 102°59′E), Gansu Province in China from 2004 to 2018. A split block design was also arranged in the experiment. The treatments included two tillage practices with No-Tillage with Stubble (NTS) and Traditional ploughed fallow (TS), where the subplots were three planting patterns with the Single Wheat (W), the Intercropping of Wheat and Maize (W/M), and the Intercropping of Wheat and Soybean (W/S). There were a total of six treatments each with three replicates. A systematic investigation was made to clarify the effects of long-term no-tillage with the crop stubbles on the spring wheat yield, in terms of the spring wheat yield, yield components, and evolution of agronomic characters. The stability and sustainability of crop yield were also analyzed under the different planting patterns of spring wheat. The research period was divided into 2004-2012 and 2013-2018. The varieties of planting crops were changed uniformly in 2013, according to the crop yields. The results showed that there was a zigzag annual fluctuation in the grain yield of spring wheat, indicating the overall upward trend under the three spring wheat planting patterns of W, W/M, and W/S. The varieties of spring wheat posed no influence over the yield increase of no-tillage with the stubble before and after the year 2012, compared with the traditional ploughed fallow treatment. The average grain yield increased significantly, as the grain number per spike increased from 2004 to 2012, particularly with the extension of planting years. Specifically, the spring wheat variety of "Yongliang 4" significantly increased by 8.25% (W), 5.65% (W/M), and 4.30% (W/S) (P<0.05), respectively, under the tillage practices of no-tillage with stubble. Furthermore, the average grain yield increased by 10.47% (W) and 10.20% (W/M) (P<0.05), respectively, for the spring wheat variety of "Longchun 26" under the planting patterns of no-tillage with stubble, as the 1 000-grain weight of spring wheat increased from 2013 to 2018. It infers that the spring wheat growth was promoted by the higher spike length suitable for the higher spring wheat yield under the W/M planting patterns in the no-tillage with stubble. There was also no significant effect of the long-term no-tillage with the stubble on the spike number and harvest index of spring wheat under the planting patterns (P>0.05). More importantly, there was no full consistence with the yield of spring wheat in the yield components. The reason was that the yield of spring wheat significantly increased by the superposition among the yield components under the tillage practices of long-term no-tillage with stubble. Meanwhile, the long-term no-tillage with stubble reduced the inter-annual fluctuation of spring wheat yield, further improving the stability and sustainability of spring wheat yield. Particularly, the intercropping greatly contributed to the more sustainable and stable yield production capacity, compared with the monoculture. Path analysis showed that the mean daily temperature, precipitation, and grain number per spike played important roles in the spring wheat yield. By contrast, the stability of spring wheat yield depended mainly on the harvest index and the mean daily temperature. Additionally, the spike length and yield determined the yield sustainability of spring wheat. Therefore, the no-tillage with stubble was the feasible tillage practice under the spring wheat planting patterns of W, W/M, and W/S in the Hexi Oasis Irrigated Areas with the extremely serious degradation of wind erosion.