Potato growth, yield and water productivity response to different irrigation and fertilization regimes

To achieve improvement in irrigation management and maximize water productivity (WP), knowledge on potato crop growth and seasonal crop evapotranspiration (ETc) in relation to combined irrigation and fertilization, are needed. In a two-year experiment conducted in Sicily (South Italy), the combined effects of 3 irrigation levels [irrigation only at plant emergence, irrigation at 50% of maximum evapotranspiration (ETm) and irrigation at 100% ETm] and 3 N-P-K fertilization rates (low: 50, 25 and 75 kg ha−1, medium: 100, 50 and 150 kg ha−1 and high: 300, 100 and 450 kg ha−1 of N, P2O5 and K2O) on ETc, crop growth rate, aboveground dry biomass and tuber dry yield, sink/source (tuber yield/aboveground biomass yield) ratio, water productivity and crop drought response factor, were studied. Irrigation water amounts were 25 mm in plots irrigated only at plant emergence in both years, 87 and 96 mm in plots irrigated at 50% of ETm, 174 and 192 mm in plots irrigated at 100% of ETm, respectively in the two years. Irrigation based on 100% of ETm + high rate of N-P-K fertilization proved the best combination to promote ETc, crop growth, and improve aboveground biomass, tuber yield, and sink/source ratio but not WP. Fertilization played a crucial role in enhancing WP of this crop especially in plots irrigated only at plant emergence, where both low and medium fertilization rates allowed maximizing WP (2.3 kg m−3 dry weight) ensuring an acceptable tuber yield (about 3.7 t ha−1 dry weight). These results are of considerable importance to farmers to achieve more efficient and rational use of water by potato grown in very limited water availability environments.