Superabsorbent polymers influence soil physical properties and increase potato tuber yield in a dry-farming region

Superabsorbent polymers, new water-saving materials and soil conditioners, are used widely in dry-farming agriculture. However, little is known about their effects on the soil physical properties under dry-farming conditions. To elucidate the effects of two SAPs (Wote and microbe) at different doses on the soil bulk density, water status, potato growth, yield, and economic benefit in a dry-farming region, we conducted a 2-year fixed field position experiment in the semiarid drought-prone area of Ningxia, China. The two SAPs were diluted 1:10 (product:soil) and applied at different rates before planting, i.e., Wote SAP 30 kg ha(-1), Wote SAP 60 kg ha(-1), Wote SAP 90 kg ha(-1), microbe SAP 30 kg ha(-1), microbe SAP 60 kg ha(-1), and microbe SAP 90 kg ha(-1). The treatment without SAP was used as the control. The tilth soil bulk density decreased under different SAP doses compared with the control, and the soil total porosity improved greatly, where the Wote SAP treatments had the greatest effects. The soil bulk density (0-60 cm) under Wote SAP 90 kg ha(-1) was significantly decreased by 6.4% compared with the control. The Wote SAP treatments had the greatest effects on water conservation during the critical potato growth stage, where the soil water storage (0-100 cm) was significantly higher than the control. The Wote SAP treatments promoted potato growth in the later period, where the plant height and stem diameter were higher than the control. Higher yield and commodity rate improvements were achieved by the application of Wote and microbe SAP compared with the control, where the optimum dose was 60-90 kg ha(-1) for Wote SAP. The application of Wote SAP 90 kg ha(-1) significantly increased crop water use efficiency compared with no SAP, and the commodity rate was highest with Wote SAP 60 kg ha(-1). The mean potato yield, commodity rate, and net income increased significantly using Wote SAP at 60 and 90 kg ha(-1), i.e., by 38.2 and 50.5%, 18.5 and 14.1%, and 28.5 and 35.0%, respectively, compared with no SAP. The application of SAPs can decrease soil bulk density and significantly improve soil porosity and soil water conservation capacity, thereby promoting potato growth. The application of Wote SAP 60-90 kg ha(-1) significantly increased potato yield and net income in a dry-farming region of Ningxia, China.