Nitrogen use efficiency for grain and protein production by rice genotypes

Abstract

A greenhouse experiment was conducted to evaluate the nitrogen use efficiency (EUN) in relation to grain production (PG) and crude protein content (PB) of nineteen cultivars of rice. Fifteen of them are adapted to soils of low levels of nutrients from the state of Maranhão, Brazil. They were chosen according to their contrasting capacity to accumulate proteins. The other four cultivars were bred to give high yields under 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 after planting. Nitrogen increased the level of protein production but did not influence PG. These results induced a lower EUN for grain and protein production for all cultivars. There were genotypic significative differences for EUN and its components: uptake and utilisation efficiency. 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.