No-tillage systems can change the ratio between soil acidity components and crop yields over the course of time. High crop yields are not seldom observed in highly acid soils. The liming criteria established for conventional tillage soils are likely to be unsuitable for no-tillage soils. The objective of this report was to define liming criteria, based on the yield response to different soil acidity levels and layers in no-tillage systems. Six plantations were sampled in the Planalto region of the state of Rio Grande do Sul, Brazil, with very distinct soil acidity conditions, and that have been cultivated in no-tillage system over a long period. Soil samples were taken from two soil layers (0-10 and 0-20 cm) and yields determined at 20 sites of each plantation. Based on regressions between relative grain yield and soil acidity indexes, it can be concluded that none of the soil acidity indicators individually can properly describe crop yield in the no-tillage system. Though significant, the relations between soil acidity indexes and crop yield were low and similar, independent of the soil layer. Thus, either soil layer can be used for liming diagnostic in no-tillage.
pH; aluminum saturation; base saturation; no-tillage; grain yield
