A crop rotation experiment involving corn, soybean, sunflower, and green manure was carried out in a Red-Yellow Podzolic soil. In some of the 12 plots with sunflower the seed germination was poor and the plants showed reduced growth, with leaf chlorosis, curved main roots, and fewer and thicker secondary roots. Yield was negatively correlated with the intensity of these symptoms. The grain yield was highly correlated with soil pH (r = 0.95) and soil base saturation (r = 0.92). Plant height and head diameter also showed linear relationship with those soil indices. The results obtained show that sunflower is very sensitive to soil acidity, and that the exchangeable aluminum criterion is inadequate for determining lime requirement for sunflower.
sunflower; Helianthus annuus; soil acidity; liming; base saturation