Response of Upland Rice Genotypes to Soil Acidity

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 without and with 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.