Effect of irrigation and fertiliser doses on sweet corn yield, water consumption and water utilization

The experiment was conducted within a framework of a two-factor long-term trial at the Research Institute for Fisheries, Aquaculture and Irrigation, in Szarvas, Hungary. This was a special field experiment, in which lysimeters have been installed in the middle of 32 m2 field plots. The main factor was the water supply with 4 levels: i1: non-irrigated control; i2: irrigated with one third of the optimal water supply; i3: irrigated with two thirds of the optimal water supply; i4: optimum irrigated plot, according to the requirement of sweet corn test plant. The amount of released irrigation water was 0, 54, 106 and 158 mm per year on average over 5 years. Within every water supply treatment there were 4 nutrient supply rates (N): N1, N2, N3, N4 = 100, 200, 300 and 400 kg ha−1 NPK fertiliser substance in ratio 2:1:1. The number of replications was 4, and the experiment was arranged in split-plot design. In the studied years, the amount of precipitation varied between 92 and 264 mm from sowing to harvesting.The effect of fertiliser was less in the non-irrigated treatments compared to that of the irrigated ones, and the yield was increased only up to 200 kg ha−1 NPK treatment level. The NPK dose of 300 kg ha−1 proved to be optimal in the irrigated treatments in which the utilization of fertilizer doses increased parallel to the improving water supply. In addition, the ratio of first class products (cobs longer than 20 cm) increased to a greater extent than the yield as a result of irrigation and fertilization. Water requirement of sweet corn proved to be between 400–450 mm resulting in an average yield of 20–24 t ha−1, of which 18–20 t ha−1 came from marketable cobs. The amount of evapotranspiration fluctuated between 270–440 mm during the five years, depending on the quantity of water supply, but it changed to a lesser extent than the amount of the yield. Increasing the fertilizer dose practically did not affect ET in non-irrigated plants, but increased it by 20–30 mm in irrigated ones. The change was not significant.The productivity of ET was only 30–45 kg ha−1 mm−1 in the non-irrigated treatment, while it was 50–55 kg ha−1 mm−1 in the irrigated treatments, with higher values at the higher fertiliser rates. The productivity of irrigation water exceeded far over the productivity of ET at adequate nutrient supply. The yield increase per 1 mm of irrigation water was on average 60 kg ha−1 mm−1, which was considerably higher than the productivity of ET of non-irrigated plants (39 kg ha−1 mm−1). There was a positive correlation between the yield and ET, and a negative correlation between the yield and specific water consumption. Irrigation and fertilization increased the average yield to a greater extent than evapotranspiration, so as the average yield increased, the ET per unit of yield decreased, i.e. the productivity of evapotranspirated water increased.