The deep-rooted safflower (Carthamus tinctorius L.) may be able to take up nutrients, especially nitrogen (N), that have been leached below the rooting zone of other crops. Following our earlier experiments conducted under rainfed conditions, this study investigated safflower yield response to N application under irrigation. The split-plot experiment with four replicates was conducted in 2002-03 and 2003-04 in farmer's fields in Lebanon's Bekaa Valley. Irrigation was the main plot and N was the sub-plot. There were four irrigation treatments: 0, 1, 2, and 3 flood irrigations, and four N rates: 0, 40, 80, and 120 kg/ha. The mean soil mineral N (0–60 cm) was 37.5 mg/kg in 2002–03, and 31.3 mg/kg in 2003–04. Combined analyses of variance over years were carried out. N increased straw yield, but decreased harvest index, thus no response of seed yield to N application was detected. There was significant seed yield response to irrigation, but all interactions were non-significant. N did not increase the numbers of heads and hundred seed weight. Results showed that safflower is an efficient user of carryover N from prior cropping. Besides saving on the cost of N fertilizers, safflower cropping may reduce non-point pollution of N to ground water and rivers.
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