EFFECT OF IRRIGATION AND NITROGEN ON WATER-USE EFFICIENCY OF WHEAT IN SAUDI-ARABIA

Water use efficiency (WUE) and yield of wheat were determined in a field experiment using different irrigation waters, with and without nitrogen fertilizer on a sandy to loamy sand soil during 1991-1992 and 1992-1993. Depending upon different fertilizer treatments, the mean crop yield ranges in 1992-1993 were: biomass 4290-13 960 kg ha(-1) (well water) and 6460-14 870 kg ha(-1) (aquaculture effluent) and grain yield 770-5010 kg ha(-1) (well water) and 2140-5790 kg ha(-1) (aquaculture effluent). The WUE for grain yield in 1991-1992 was 2.67-12.24 kg ha(-1) mm(-1) (well water) and 4.29-12.67 kg ha(-1) mm(-1) (aquaculture effluent). The WUE for grain yield in 1992-1993 was 1.22-7.97 kg ha(-1) mm(-1) (well water) and 3.40-9.21 kg ha(-1) mm(-1) (aquaculture effluent). The WUE for biomass in 1991-1992 ranged between 8.74-29.16 kg(-1) ha(-1) mm(-1) (well water) and 11.34-30.02 kg ha(-1) mm(-1) (aquaculture effluent). Whereas in 1992-1993, the WUE for biomass was 6.82-22.19 kg ha(-1) mm(-1) (well water) and 8.68-23.64 kg ha(-1) mm(-1) (aquaculture effluent). The grain yield and WUE obtained in T4 and T5 irrigated with well water and receiving 75 and 100% nitrogen requirements, were comparable with T4 and T5 irrigated with aquaculture effluent and receiving 25 and 50% nitrogen requirements. It is, therefore, concluded that application of 150-225 kg N ha(-1) for well water irrigation and 75-150 kg N ha(-1) for aquaculture effluent irrigation containing 40 mg N l(-1) would be sufficient to obtain optimum grain yield and higher WUE of wheat in Saudi Arabia.