Rice nitrogen fertilization under supplemental sprinkler irrigation

The objective of this study was to determine adequate N level for modern up land rice (Oryza saliva L.) cultivars sown at 0.20 m row spacing under supp lemental sprinkler irrigation. The effects of N levels (0, 40, 80, 120, and 160 kg of N/ha) on the yield of one cultivar (Maravilha) and three favoura ble upland rice lines (CNA7127, CNA7730, and CT7/15) were studied during th ree crop seasons, in Santo Antonio de Goias, GO, Brazil, in a Dark Red Lato sol. According to regression model used, the maximum rice grain yield was 5 ,523 kg/ha, obtained with 112.9 kg of N/ha. Considering the prices of N (R$ 1.20) and rice (R$ 0.20) practiced in Goiania, on June/97, the economical N level was 87.3 kg/ha.