Regulated deficit irrigation strategies for different potato cultivars under continental Mediterranean-Atlantic conditions

This paper presents the calibration and validation processes of the MOPECO model for the simulation of 4 commercial potato cultivars (Zorba, Mirari, Monalisa and Leire), using the data from a three-year field experiment (years 2010, 2011 and 2012; two per cultivar) under deficit irrigation conditions in the Basque Country region of Spain. The optimized regulated deficit irrigation (ORDI) strategy was used in combination with the typical meteorological year (TMY) methodology to determine irrigation strategies aimed at increasing the irrigation water productivity of potato crop under real farming conditions and limited volumes of irrigation water. The growing degree-days for the whole growth cycle were 1958 Cd, while the calibrated crop yield response (Kr) values for the growth stages proposed by FAO-56 were 0.45 (vegetative period), 0.70 to 0.90 (yield formation), and 0.25 to 0.40 (ripening) depending on the considered cultivar. The validation results showed that MOPECO is suitable for simulating the yield versus total water (gross irrigation + effective rainfall) use under the climatic and soil conditions in this study (normalized root mean square error from 7.2 to 8.5% between observed and simulated levels). ORDI maximized the yield of the crop for different volumes of available irrigation water. The irrigation water productivity differed according to the cultivar, increasing for lower volumes of irrigation water (from 23.0 kg to 58.1 kg m(-3) for Monalisa and Mirari cultivars, irrigated with 100% and 40% of the requirements, respectively).