The effect of two irrigation intervals (I1: 7 days and I2: 14 days), four nitrogen doses (N9, N0, N1, N, and N3) and two crop coefficients (Kpc:O.60 and Kpc:0.90) on pistachio nut fertigation was studied. Irrigation water amount was calculated based on pan-evaporation. The highest Kc values were in JuIy when the highest evapotranspiration was measured. Maximum nitrogen amount was applied to treatment with high nitrogen and high water (If1N3Kpc2). In 2001, all pistachio trees received 4.9 and 3.2 g.m-2 phosphorous and potassium; in 2002 these values decreased to 4.2 and 2.8 gram/m-2. Net assimilation was between 10 and 20 mo1m2s1 in irrigated treatments. Corresponding figures for non-irrigated treatment were between 5 and 15 molm-2s-1. Photosynthetic water use efficiency, however, was about 2 molmmol1 in all treatments. Maximum yields were taken from If2N3 with average 11.7 kg /tree in 2001 and from IflN0 with average 11.6kg/tree in 2002.