Abstract:From the sub-soiling experiment during five years (2013—2017), it is preliminarily approved that the yield was obviously increased by sub-soiling applied in the continual no-tillage field. The highest yield related with sub-soiling would be happened at current season of operation, searching totally eight harvest seasons, and six seasons had the highest yield at current season of sub-soiling. Adoption of sub-soiling in summer had 5.9% higher yield than no sub-soiling, and 2.3% higher than in autumn, besides, summer sub-soiling had better power using efficiency and lower operation cost. Therefore, summer sub-soiling had better prospect on extension, but the autumn sub-soiling would be preferentially adopted in drought summer and poor irrigation area. An outstanding event in the trial was the decline of yield increasing rate, for summer sub-soiling, the first year had 18% of yield increase, since then, the yield increasing rate was quickly declined to 6.3%, 3.9%,3.4% and 1.7% in the second, third, fourth and fifth year. The decline of yield increase rate reflected double aspects of sub-soiling influence. It had positive aspect by loosing soil and holding more water in the field, but also had negative aspect by depressing of sowing quality, reducing of soil organic matter content and soil bacteria. The negative influence would be accumulated year by year, thus yield increase rate was gradually declined. Sub-soiling was an energy consuming operation, from roughly calculation, while yield increase rate was lower than 2% around, adoption of sub-soiling became input larger than output. From the yield decline trend in the trial, at fifth year of continued summer sub-soiling, at third year of continued autumn sub-soiling, the yield increase rate would reach the turnoff point. To reasonably determine the period of sub-soiling, further experiment was necessary.
