AbstractYields of dry beans on a Corozal clay (Ultisol) dropped sharply when acidity increased beyond pH 4.7 and with 30% Al saturation of the effective CEC of the soil. No crop was produced at pH 4.1 with 80% Al saturation. Similar results were obtained on a Corozal clay subsoil, but the effect of increasing acidity on bean yields was much more marked. Lower yields were obtained on a Coto clay (Oxisol) with a relatively small response to soil acidity. For all soils combined, pH and percent Al saturation of the exchange capacity of the soil correlated very closely with yields. There was also a positive correlation between Ca content of the leaves and yields. Highest yields were obtained around pH 5.2 when there was essentially no exchangeable Al in the soil. Yields decreased to about 50% of maximum when Al saturation increased to 50%, and no yields were produced when Al saturation of the soil approached 80%.
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