Response of potato to full and deficit irrigation under semiarid climate: Agronomic and economic implications

• Deficit irrigation can increase profits of potato under limited water and land resources.
• Deficit irrigation at tuber bulking gave 12% lower yield than well irrigated control.
• Deficit irrigation at tuber ripening gave 42% lower yield than well irrigated control.
• When water is the limiting factor, yield maximizing level of water use is inappropriate.
• Profit maximizing level when land is limiting factor can be adopted where there is no water shortage.

Yield, cost, and revenue functions of potato (cv. Agria) were developed from field experiments in 2007–2008, which were designed to determine the response of tuber yield to no irrigation for two weeks at tuber bulking (TB) and tuber ripening (TR). Deficit-irrigated treatments were compared to a well-irrigated control (C) throughout the growing season. The yield-profit maximization methodology of English (1990) was reviewed and a new procedure based on optimization software was proposed. Treatment with deficit irrigation at TB achieved marketable yield 12% lower than that obtained in the well-irrigated control (60.5 Mg ha−1), whereas deficit irrigation at TR reduced tuber yield by 42%, compared to the control. However, yield reduction was compensated by an increase in tuber dry matter in the deficit-irrigated treatments. The results of the newly proposed yield-profit maximization procedure show that when land is limiting, the level of water applied at which net income per unit of land is maximized (Wl) fits the yield maximizing (Wm) strategy, while when water is limiting, the level of water applied at which net income per unit of water is maximized (Ww) would result in as much water saving as 10–15% of total applied water. The results also suggest that the target yield that was obtained in the treatment with deficit irrigation at tuber bulking (53.6 t ha−1) was in the range of 500–560 mm of water application. We concluded that deficit irrigation at tuber bulking for two weeks is a suitable scenario for potato farming, with potential benefits resulting from reduced irrigation costs.