Deficit irrigation of potato

Potato (Solanum tuberosum L.) can respond to water stress with yield reductions and loss of tuber grade. The economic opportunities to practise deficit irrigation are more limited for potato than for some other crops. Four potato varieties were grown under four, season-long, sprinkler irrigation treatments during three successive years (1992-1994) on a silt loam soil in eastern Oregon, United States of America. The check treatment was irrigated when soil water potential (SWP) at the 0.2-m depth reached -60 kPa. This treatment received at most the accumulated evapotranspiration (ETc) to avoid exceeding the water holding capacity of the top 0.3 m of soil. The three deficit irrigation treatments were irrigated when SWP at the 0.2-m depth reached -80 kPa and had the following percent of the accumulated ETc applied at each irrigation: (i) 100 percent, (ii) 70 percent, and (iii) 50 percent, with 70 percent during tuber bulking. Based on regression of applied water over three years, potatoes lost both total yield and grade when irrigations were reduced. Based on regression of applied water reductions in irrigation, gross revenues declined more than production costs, resulting in reduced profits. The results of this case study suggest that deficit irrigation of potatoes in the semi-arid environment of eastern Oregon would not be a viable management tool because the small financial benefits would not offset the high risks of reduced yields and profits from the reduced water applications. Results from eastern Oregon are compared with those obtained elsewhere. (author)