RESPONSE OF UPLAND RICE GENOTYPES TO SOIL ACIDITY

Authors: FAGERIA, N - EMBRAPA, BRAZIL; CASTRO, E - EMBRAPA, BRAZIL; Baligar, Virupax

Submitted to: The Red Soils of China: Their Nature, Management and Utilization
Publication Type: Book / Chapter
Publication Acceptance Date: 12/9/2003
Publication Date: 5/1/2004
Citation: Fageria, N.K., Castro, E.M., Baligar, V.C. 2004. Response of upland rice genotypes to soil acidity. The Red Soils of China: Their Nature, Management and Utilization. The Netherlands. Kluwer Academic Publications. p. 233-252.

Interpretive Summary: On highly weathered soils in many parts of the world, soil acidity is the major yield-limiting factor for crop production. In Brazil, upland rice is mainly grown on Oxisols and on these soils, acidity and low fertility are the major factors for low rice yields. A greenhouse experiment was conducted to evaluate the response of upland rice genotypes to low and high soil acidity of Oxisols. Soil acidity effects on growth, grain yield, yield components, and macro-micro nutrient use efficiency of genotypes was also assessed. Upland rice genotypes used differed significantly in grain yield, yield components and nutrient use efficiency in relation to soil acidity. Over all, soil acidity reduced grain yield in all the genotypes. One of the mechanisms of acidity tolerance in upland rice genotypes appears to be their higher nutrient utilization efficiency. Acid soil tolerant and higher nutrient use efficient genotypes identified from such studies could be used in a breeding program to produce high yielding upland rice cultivars. Use of such improved cultivars in upland rice farming systems appears to be one of the important management strategies in improving rice yield potentials on acidic and low fertility Oxisols.

Technical Abstract: In many parts of the world where the soils are highly weathered Oxisols, acidity is one of the major factors that contributes to the reduction of crop yields. In addition to liming, use of acid tolerant crop species or cultivars within species, is a complementary solution for the improvement of crop production on such soils. A greenhouse experiment was conducted to evaluate the response of 20 upland rice (Oryza sativa L.) genotypes to two levels of soil acidity. An Oxisol (Typic Haplustox) was amended with and without dolomitic lime (6g /kg soil) to achieve pH values of 4.5 (High soil acidity) and 6.4 (Low soil acidity). At both soil acidity levels, genotypes differed significantly in growth parameters, grain yield and yield components. Grain yield and most of the yield components were significantly decreased at low soil acidity as compared with high soil acidity, demonstrating the tolerance of upland rice genotypes to soil acidity. The majority of the genotypes that produced higher yields at high soil acidity did not produce high yields at low soil acidity level, demonstrating strong genotype x acidity interactions. Grain yield gave positive significant correlations with plant height, shoot dry weight, panicle number, grain harvest index, and 1000- grain weight, and it had negative and significant correlation with spikelet sterility. Genotypes differed significantly in nutrient use efficiency and there were also significant acidity x genotype interactions for almost all nutrient use efficiencies, for grain production. Grain yield gave significant negative correlations with soil pH, Ca saturation and base saturation. Grain yield gave significant positive correlations with soil Al, H+Al, and CEC, confirming that upland rice genotypes are tolerant to soil acidity.