Effects of different sub-soiling frequencies incorporated into no-tillage systems on soil properties and crop yield in dryland wheat-maize rotation system

No-tillage has become a universal management system to conserve soil water and sustain soil productivity in dryland agriculture. However, no-tillage in a long-term may produce some undesirable soil characteristics. An occasional tillage operation has been used as a mean to manage some of the defects that have emerged in NT farming systems. This study was to explore the effect of sub-soiling at different frequencies in a no-tillage farming system of an annual cropping system of winter wheat-spring maize rotation on Loess Plateau. The study consisted of three tillage practices: NT (no-tillage were applied every year), NT/ST (no-tillage were applied in first year and rotated with sub-soiling in second year), NT/NT/ST (no-tillage were applied in first two year and rotated with sub-soiling in third year). The study began in 2007 on a former spring maize field with conventional tillage and lasted for three-year rotation cycles by 2016. In ten years, for the soil physical properties, NT/ST rotation significantly decreased soil bulk density, and increased soil porosity and amount of macroaggregates (>0.25 mm) when compared to NT (P < 0.05). For water storage, NT with ST rotations (NT/ST & NT/NT/ST) increased the soil water storage in the fallow periods. Moreover, NT/ST rotation produced higher average grain yields, WUE and economic profit in the winter wheat-spring maize cropping system when compared to NT over the ten years. However, the soil organic matter (SOM) and total N under NT with ST rotations (NT/ST & NT/NT/ST) were lower than it for NT. For this long-term experiment, NT provided a better soil nutrient condition, NT/NT/ST and NT/ST rotation showed a better effect on soil water storage in fallow. For the comprehensive productivity, NT/ST rotation showed a balanced soil properties and crop production effect among three tillage treatments. In the winter wheat-spring maize cropping system, NT/ST rotation enhanced soil physical and chemical properties and increased yield and water holding capacity of soil. We predict that the NT/ST rotation will be of great significance in promoting the development of rain-fed conservation farming in the Loess Plateau of China.