Abstract: The right tillage methods can improve the capacity of soil to supply water to crops and promote root development. This can result in better drought resistance of crops and higher productivity. Therefore, this is a promising strategy to increase the yield and water-use efficiency of potato (Solanum tuberosum) crops in a semiarid area. This study was conducted at the Dingxi Experimental Station of the Gansu Academy of Agricultural Sciences. The station is located in the northwest of Loess Plateau (Anding District, Dingxi, Gansu Province, 104°36' E, 35°35' N) at an altitude of approximately 1970 m. The field experiment was conducted under ridge-furrow planting and plastic-mulching conditions in 2016 and 2017. Potato (Longshu 10) was used as the material, and the three treatments included: 1) vertical rotary sub-soiling to 40 cm depth (VRT); 2) sub-soiling to 40 cm depth (DLT); and (3) traditional tillage to 15 cm depth (TT). The experimental design was a randomized block with three replicates, and the area of each plot was 10 m×6 m. The soil bulk density, soil total porosity, capillary porosity, soil saturation moisture content, capillary moisture content, field water capacity, soil wilted moisture content, total soil water content, and tuber yield were investigated. In addition, soil available water storage, evapotranspiration (ET), and water-use efficiency (WUE) were calculated to determine the effect of the different tillage treatments on soil water characteristics, potato tuber yield, and WUE. The results showed that VRT significantly decreased the soil bulk density; by 10.8%-25.3% and by 13.8%-24.8% as compared with DLT and TT, respectively. Compared with DLT and TT, VRT increased total soil porosity and capillary porosity by 12.3%-23.7% and 29.7%-46.6%, respectively, increased the soil saturation moisture content and capillary moisture content by 26.1%-54.4% and 38.8%-82.9%, respectively, and decreased the soil wilted moisture content by 11.0%-49.0%. Compared with the TT treatment, the DLT treatment resulted in lower soil bulk density and soil wilted moisture content, and higher soil saturation moisture content, capillary moisture content, total soil porosity, and capillary porosity. The optimized soil physical and hydrographic characteristics resulted in significant increases in soil available moisture in VRT (34.3%-136.9% higher than in DLT and 44.6%-575.2% higher than in TT). The soil available moisture content in the 20-40 cm soil layer was much higher in DLT than in TT. The significant increase in soil available water content in VRT resulted in increased potato plant growth (by 24.8%-156.8%), increased potato tuber yield (by 47.8%-41.0%), and increased WUE (by 18.9%-92.3% and 19.2%-26.6%), as compared with those in the DLT and TT treatments. The observed differences among the treatments were significant, and were greater in the drought year (2016) than in the normal year (2017). Consequently, VRT optimized the soil physical and hydrographic characteristics, increased soil available moisture, increased potato development and tuber yield, and improved WUE, with stronger effects in the drier year (2016). Thus, VRT is a promising method to improve drought resistance and increase the water-use efficiency of crops on the semiarid Loess Plateau.

Key words: vertically rotary sub-soiling, soil physical characteristics, soil available moisture, potato, tuber yield, semiarid Loess Plateau