There are few studies about the use of phosphorus and potassium in irrigated rice (Oryza sativa L.) in the State of Roraima. The objetive of this study was to evaluate the response of rice to the application of different doses of phosphorus and potassium (0, 50, 100, 200 and 400 kg ha-1 P2O5 K2O) on productivity, plant height and yield composition in an area in the first year of cultivation. A randomized blocks design was used in a split plot with four replicates. A regression analysis was PERFORMED using surface response. The potassium significantly and positively affected all variables except weight of thousand grains, reducing it linearly. wits its effect being the responsible for the achieved productivity. The phosphorus positively influenced the weight of thousand grains and productivity. The number of grains per panicle, the weight of thousand grains and plant height contributed decisively to the yields achieved. The higher productivity found (8,154 kg ha-1 grains) occurred with the use of 304 kg ha-1 P2O5 and 228 kg ha-1 K2O. The maximum economic efficiency was obtained with 134 and 158 kg ha-1 P2O5 and K2O, respectively, and yield of 7,501 kg ha-1 grain, providing net earnings of R$ 696.78 ha-1, benefit / cost ratio of 1.18 and unit cost of R$ 0.5271 kg-1 rice.
Oryza sativa L.; correction of fertility; economic analysis
