Nitrogen promotes large benefits to flooded rice. However, little is known about its effects on infested fields, especially with red rice, which is the species that causes the highest damage to flooded rice in Rio Grande do Sul, Brazil. Two experiments were conducted at greenhouse and growth chamber conditions, to compare the efficiencies of uptake and utilization of nitrogen by the cultivar BR-IRGA 410 with two red rice ecotypes, at the growth stages of initial tillering and beginning of panicle differentiation. It were used studies on kinetics of nitrogen uptake by plants in nutrient solution and the analysis of concentration and amount of nitrogen in plants. In the beginning of the tillering, stage with low competition by light, the three genotypes show similar efficiencies on nitrogen uptake. Nitrogen fertilization at beginning of panicle differentation is more advantageous to red rice than to rice, dueto its higher efficiency on nitrogen uptake and utilization.
Oryza sativa; weed; competition; morphologic traits; fertilization