NITROGEN USE EFFICIENCY FOR GRAM AND PROT EIN-PRODUCTION BY RICE GENOTYPES

A greenhouse experiment was conducted to evaluate the nitrogen use eff iciency (EUN) in relation to grain production (PG) and crude protein c ontent (PB) of nineteen cultivars of rice. Fifteen of them are adapted to soils of low levels of nutrients from the state of Maranhao, Brazi l. They were chosen according to their contrasting capacity to accumul ate proteins. The other four cultivars were bred to give high yields u nder optimal agricultural conditions. They were grown in pots with and without addition of foliar N (0.035 g N/plant) applied 10 and 20 days after flowering as N-URAN. All plants received 0.07 g of N/plant afte r planting. Nitrogen increased the level of protein production but did not influence PG. These results induced a lower EUN for grain and pro tein production for all cultivars. There were genotypic significative differences for EUN and its components: uptake and utilisation efficie ncy. Cultivars bred for higher yield had higher EUN due to its greater N uptake efficiency. To the non-bred ones, EUN was more dependent on higher capacity for N remobilization. The non-bred cultivars Arroz de Revenda, Cana Roxa, Ligeiro Vermelho and the bred IAC-899 and IAC-1278 had the greatest EUN values.