EFFECT OF IRRIGATION WATER AMOUNTS ANDNITROGEN RATES ON OPTIMUM MAIZE YIELD AND NETRETURN UNDER DRIP IRRIGATION SYSTUM ATNORTHWEST DELTA, EGYPT

Two field experiments were carried out at Wady Elnatron, El-Behera Governorate, Wady Elnatron located in the west desert near the Delta about 90 kilometers north west of Cairo, during 2008 and 2009 seasons to study the effect of irrigation water amounts and nitrogen rates on maize yield and the net return from these treatments under drip irrigation system. Split plot design was used with four replicates. The main plots were assigned by four irrigation water amounts (100 %, 90 %, 80 % and 70 %) of evapotranspiration (ETc). The sub-plots were randomly assigned by four nitrogen rates (zero, 50, 100 and 150 kg N fed^-1 Four polynomial quadratic equations were established to show the following results: ) as ammonium nitrate (ha = 2.4 fed^-1). The other recommended agriculture practices were done. 1. The maximum and optimum N rates (X_m and X_opt) were increased by decreasing irrigation water amounts from 100% to 70% of ETc in the two seasons. 2. The maximum and optimum maize yields (Y_m and Y_opt) were decreased by decreasing irrigation water amounts from 100% to 70% of ETc in the two seasons. 3. The highest maximum yield (4.307 ton fed^-1), the highest total value of yield (6394.5 L.E fed^-1) and the highest return of N fertilizer (1744.5 LE fed^-1 4. The efficiencies of N rates (eX) were decreased by increasing N rates from N_0 to N_1, N_2 and N_3, respectively with different irrigation water amounts. ) were obtained with 100 % of ETc used in the two seasons. 5. The relative efficiency (E_X), the efficiency of nitrogen fertilizer at optimum rate (eX_opt) and the efficiency of soil nitrogen (eX_s) were decreased as irrigation water amounts decreased. 6. The soil nitrogen content during plant growth (X_s) was decreased as irrigation water amounts decreased. 7. The contribution of soil N was decreased as irrigation water amounts decreased in the two seasons. 8. The contribution of N fertilizer was increased by increasing N levels in the two seasons.