Interactive effects of autumn tillage with mulching on soil temperature, productivity and water use efficiency of rainfed potato in loess plateau of China

Low precipitation and temperature fluctuations are key limiting factors that influence the potato tuber yield in rainfed areas of the Loess Plateau, China. The implementation of tillage with mulching during fallow after the autumn harvest may be an effective management strategy to help reduce soil evaporation and conserve more soil water for spring sown potato. We conducted a three-year field experiment in a semiarid area of the Loess Plateau in 2014–2015, 2015–2016, and 2016–2017 to study the interactive effects of autumn tillage and mulching practices during fallow on the soil temperature, moisture, tuber yield, and water-use efficiency of potato. The treatments comprised three tillage systems in the main plots, i.e., no-tillage (NT), subsoiling (ST), and plowing tillage (PT), and three mulching methods in the subplots, i.e., straw mulch (SM), plastic-film mulch (PM), and no mulch (NM), in a replicated split plot design. Autumn tillage with mulching during fallow significantly influenced the soil water storage, especially in the early growing season of potato. Among the mulching methods, SM and PM increased the mean soil water storage by 6.3% and 5.9% (P < 0.05), respectively, compared with the NM plots. Conservation tillage combined with PM (NT×PM and ST×PM) significantly increased the topsoil temperature, whereas conservation tillage combined with SM (NT×SM and ST×SM) significantly decreased the temperature, which could have improved the topsoil conditions for potato tuber yield formation in the three experimental years. Among the tillage systems, the PM plots increased the mean topsoil temperature by 2.4°C (P < 0.05), whereas the SM plots reduced the temperature by 3.0°C (P < 0.05) during the whole period. The beneficial effects of the changes in moisture and temperature in the PM and SM plots improved the tuber yield of potato, in comparison with NM plots. Tillage and mulching had significant interaction effects on the potato tuber yield and water-use efficiency. The highest mean potato tuber yields were obtained in the ST×SM and NT×SM treatments, respectively, which were 41.0% and 35.3% higher (P < 0.05) than those with the PT×NM treatment. The three-year mean water-use efficiency increased significantly by 50.5% and 39.9% (P < 0.05) under the ST×SM and NT×SM treatments, respectively, and the three-year mean rainwater-use efficiency increased by 30% and 29% (P < 0.05) when compared with CT×NM treatment. Overall, our findings demonstrate that conservation tillage with SM and PM significantly increased the potato tuber yield and water-use efficiency. Considering the years with warm and dry climate conditions, we recommend conservation tillage with SM may be a more efficient method for improving the potato productivity, WUE and RUE in the semiarid region of the Loess Plateau.