Potato performance as influenced by the proportion of wetted soil volume and nitrogen under drip irrigation with plastic mulch

Scarce water resources and substantial food demands require efficient water use in arid Northwestern China. Field experiments were conducted to investigate the effects of the proportion of wetted soil (P) and nitrogen fertilizer (N) on potato yield, crop evapotranspiration (ETc), water use efficiency (WUE), and quality under drip irrigation with plastic mulch. In 2012, a factorial trial was conducted with two soil wetting proportions (40% and 70%) and five N rates (90, 135, 180, 225 and 270 kg N ha−1). In 2013, a factorial trial tested two soil wetting proportions (50% and 75%) and four N rates (90, 150, 210 and 270 kg N ha−1). Results showed that seasonal ETc was greater with higher P, but the difference in ETc was not significant among different N rates. Although tuber yields of different P levels were not statistically different, yields with lower P were numerically larger than with higher P. The water was used more efficiently with lower proportions of wetted soil. Potato yield, WUE, and tuber starch and vitamin C content responded quadratically to the rate of applied N. Tuber protein was positively and linearly correlated with the N rate. The results suggest that potato could be cultivated with a moderate P (40-50%) and an intermediate rate of applied N (135-150 kg N ha−1) under drip irrigation with mulch, achieving acceptable yields and quality while saving irrigation water and conserving N fertilizer.