Assessment of flood irrigation regimes on nitrogen use efficiency for sugar beet

Mismanagement of nitrogenous fertilizers has caused serious nitrate (NO3) contamination in many flood-irrigated. Low-volume irrigation practices can offer an alternative approach for controlling NO3 leaching and agricultural water use. The simultaneous application of fertilizers and irrigation water is an appropriate alternative to increase the efficiency of applied water and fertilizers. The nitrogen use efficiency of sugar beet (Beta Vulgaris L.) has been studied through the Iran but there is limited information about the response to irrigation and amount nitrogen fertilizer. The objective of this study was to investigate the effect of various irrigation and nitrogen amounts on efficiency of applied fertilizers. A field experiment with sugar beet as randomized block, split-plot design with irrigation treatments as main plots and N fertilizer rates as subplots, with three replications, was used. Four levels of the water (40, 80, 120 and 160% evaporation from surface of A class pan, treatments I1 to I4) and nitrogen fertilizer (urea) rates (N0, N1, N2, and N3, respectively 0, 90, 180 and 270 kg N ha-1 were applied. The results indicated there were significant differences (P0.01) in root yield, sugar content, total dry matter and nitrogen use efficiency (NUE) basis of root yield, sugar and total dry matter yield between treatments Treatment I4 with 47969 kg ha-1, root yield and treatment I2 with 6855 kg ha-1, sugar content had maximum production. The result showed, root yield, sugar content and total dry matter increased with increasing applied nitrogen. Treatment I4N3 with 53621 kg ha-1 root yield, 7887 kg ha-1 sugar content and treatment I3N3 with 53075 kg ha-1 root yield, 7689 kg ha-1 sugar content had maximum yield. Nitrogen use efficiency maintained an order I4>I3>I2>I1 and F1>F2>F3. There was a decreasing pattern in NUE values with increasing fertilizer rates. The results showed that by increasing applied water, nitrogen use efficiency increased and affected by fertilizers treatments. Fertilizer use efficiency also decreased by increasing fertilizer rate. The results also demonstrated there were significant differences in all the treatment.