RESPONSE OF FAVORABLE UPLAND RICE GENOTYP ES TO SOIL FERTILITY

In modem agriculture the fertilizer costs constitute a major fraction of the total cost in crop production. Under this situation growing nut rient-efficient crop genotypes would be an economical sound complement ar solution to improve crop yields and decrease cost of production on nutrient deficient soils. Two field experiments were conducted at the National Rice and Bean Research Center, Experimental Station of Capiva ra, Santo Antonio de Goias, Goias, Brazil, to evaluate the response of 29 upland rice (Oryza sativa L.) genotypes to low, medium and high fe rtility levels on an oxisol. Significant differences were found among the genotypes for grain yield. Genotypes Rio Paranaiba, Guarani, CNA 6 687, CNA 6895, CNA 7458, CNA 7470, CNA 7278, CNA 6891, Araguaia, CNA 7 451, CNA 7455 and CNA 7471 were considered the most efficient, based o n grain yield efficiency index. Genotypes were also different in accum ulation and utilization of N, P, and K. On an average, to produce one ton of rice grains, it is necessary to accumulate 32 kg of N, 5 kg of P and 27 kg of K by the crop. Average nutrient utilization efficiency (kg of grains/kg of nutrient absorbed) was in the order of P > K > N.