Effects of vertically rotary sub-soiling tillage and plastic mulching on soil physical properties and water consumption of Codonopsis pilosula in semi-arid area

To provide the theoretical basis for high-yield cultivating technology of Codonopsis pilosula, we investigated the effects of vertically rotary sub-soiling tillage (VRT) and plastic mulching on the soil physical properties and water consumption characteristics of Codonopsis pilosula on the semi-arid areas of the northwest Loess Plateau.In 2017, we used a randomized block design in a field experiment with four treatments: vertically rotary sub-soiling tillage for 40 cm depth (VT), VT with plastic mulching (VTM), traditional rotary tillage for 15 cm depth (RT), and RT with plastic mulching (RTM).We analyzed the soil bulk density, soil saturation moisture content, capillary moisture content, total soil porosity and soil capillary porosity in the 0~40 cm soil depth as well as tuber yield; and calculated the periodical water consumption, water consumption modulus coefficient, water consumption intensity, crop growth rate and water consumption rate.The results showed that compared with RTM and RT, VTM and VT significantly reduced the soil bulk density in the 0~40 cm soil depth by 8.7%~9.6% and 8.1%~9.4%, respectively; while VRT increased soil total soil porosity, soil capillary porosity, soil saturation moisture content and capillary moisture content.The vertically rotary sub-soiling tillage increased periodical water consumption, water consumption modulus coefficients and water consumption intensities by 6.1~8.8 mm, 3.2%~8.5% and 9.6%~15.2%, while the plastic mulching increased these values by 8.1~18.4 mm, 6.8%~37.1% and 13.6%~45.7%, respectively.Compared with traditional votary tillage and without plastic mulching treatment, the crop growth rate and water consumption rate from seedling to fruiting stage in vertically rotary sub-soiling tillage increased by 29.6%~75.1% and 21.4%~59.8%, respectively; while those of plastic mulching increased by 21.6%~67.7% and 16.7%~64.8%, respectively.The VRT increased tuber yield and WUE by 21.3%~34.4% and 14.1%~28.3%, while plastic mulching increased them by 18.9%~31.8% and 11.8%~25.7%, respectively.Therefore, vertically rotary sub-soiling tillage reduced soil bulk density, increased soil saturation moisture content, capillary moisture content, total soil porosity and soil capillary porosity.The combination of vertically rotary sub-soiling tillage and plastic mulching improved the water consumption, water consumption modulus coefficient and water consumption intensity from branching to tuber expanding stage, and increased the crop growth rate and water consumption rate from seedling to fruiting stage, significantly increasing the yield and water use efficiency of Codonopsis pilosula.The combination of vertically rotary sub-soiling tillage and plastic mulching would be the efficient planting technology of Codonopsis pilosula in the semi-arid area of northwest Loess Plateau.