Yield and Iron Toxicity Response of Rice Cultivars to Nitrogen and Phosphorus Application Rates in Lowland Ecology of Moist Savanna of Northern Nigeria

Evaluation of ameliorative effect of nitrogen and phosphorus rates on iron toxicity of lowland rice was examined. Trials were conducted in the Research Farm of National Cereal Research Institute, 2006 and 2007 wet season. The experiment was laid out in a randomized complete block design (RCBD) in split-split-plot arrangement replicated three times. The main blocked consisted of three levels of phosphorus (0, 30 and 60 P 2 0 5 kg ha -1 ); the sub-block four levels of nitrogen (0, 30, 60 and 120 N kg ha -1 )and the sub-sub-block ten rice varieties (five lowland NERICAs (NERICA L-19, 20, 41, 42 and 60), four improved sativa (FKR 19, TOX 4004, BW 348-1and WITA 4) and one local variety (Ebagichi). Significant interactions ( P <0.05) of phosphorus × nitrogen × variety at 42 and 63 DAT were observed on iron toxicity score with significant depression at 30 kg P 2 0 5 ha -1 of lower nitrogen rates in all varieties except NERICA L-60. Increasing application rates of nitrogen resulted in increase in grain yield, while maximum grain yield was observed at 30 kg P 2 0 5 ha -1 . WITA 4 at lower N application rates and 30 kg P 2 0 5 ha -1 remained the most promising in terms of grain yield and iron toxicity tolerance in the moist Savanna of northern Nigeria.