NITROGEN FERTIGATION TO IMPROVE NITROGEN USE EFFICIENCY AND CRUDE PROTEIN ON SILAGE CORN

This study investigated the effect of nitrogen (N) fertigation frequency and different amounts of irrigation water on drip-irrigated silage corn. Experiments were conducted in the Southeastern Anatolia region of Turkey in 2011 and 2012. A split-plot experimental design was applied. The main plots contained four different rates of evaporation from Class A pan (Ep): I-1, 50 %, I-2, 75 %, I-3, 100 %, and I-4, 125 %. Sub-plots were designed with different frequencies of N fertigation as follows: N-1: application of two-fifths of the total N when the plant height became about 50-60 cm, and the last two-fifths of it when the plants entered the stage of tasseling, N-2: application of N applied at each 2 irrigation cycles for 10 days, and N-1: application of N applied at each irrigation cycle for 5 days. One-fifth of the total N was applied to the soil at sowing in all treatment regimes. The dry matter biomass (DM) of 30 t ha(-1) and total crude protein yield of 2.0 t ha(-1) were obtained with N application of equal amounts at each irrigation cycle (5 days) and irrigation water consisting of 100 % cumulative evaporation from Class A pan (Ep) for an optimum and appropriate treatment. Nitrogen use efficiency (NUE) and irrigation water use efficiency (IWUE) were 107.7 kg DM ha(-1) N and 58.0 kg ha(-1) min(-1) (5.8 kg m(-3)), respectively. The requirement of the average value of irrigation water and the optimum wetted area ratio for drip-irrigated silage corn were 447 mm and 0.65, respectively.