Potato Growth, Photosynthesis, Yield, and Quality Response to Regulated Deficit Drip Irrigation under Film Mulching in A Cold and Arid Environment

Abstract

The effects of the amount and timing of regulated deficit drip irrigation under plastic film on potato (‘Qingshu 168’) growth, photosynthesis, yield, water use efficiency, and quality were examined from 2017 to 2019 in cold and arid northwestern China. A two-factor randomized design was used with two levels of regulated deficit irrigation (mild, moderate) applied in four stages of potato growth (seedling, tuber initiation, tuber bulking, starch accumulation). Growth and photosynthetic parameters were determined in each growth stage, and yield and quality were measured after harvest. The net photosynthetic rate, stomatal conductance, and transpiration rate decreased significantly under water deficit in the tuber formation and starch accumulation stages, and the decreases were greater with moderate than mild water deficit. Although water deficit reduced potato yields, potato subjected to mild water deficit in the seedling stage had the highest yield at 43,961.91 kg·ha−1, followed by those subjected to mild water deficit in the starch accumulation stage at 42,262.25 kg·ha−1, which were decreases of only 4.50% and 8.19%, respectively, compared with potato under full irrigation. The highest water use efficiency was in potatoes subjected to mild water deficit in the seedling stage (8.67 kg·m−3), with the second highest in those subjected to moderate water deficit in the seedling stage (8.28 kg·m−3), which were significant improvements by 10.87% and 5.84%, respectively, compared with full irrigation. The highest overall quality was in potatoes subjected to mild and moderate water deficit in the seedling stage. The starch content in potatoes with mild water deficit in the seedling stage increased by 3.34% compared with that under full irrigation. In addition, the protein and vitamin C contents in potatoes under moderate water deficit increased significantly by 0.77% and 21.59%, respectively, compared with the contents under full irrigation. Principal component analysis identified mild water stress in the seedling stage as the optimum regulated deficit irrigation regime for potato. Thus, the relative soil water content should be maintained at 55% to 65% of field capacity in the seedling stage but at 65% to 75% in the other growth stages. The results of this study provide theoretical and technical references for efficient water-saving cultivation and industrialization of potato in cold and arid northwestern China.