Analyses of Several Brazilian Soils in Relation to Plant Responses to Sulfur
1959
McClung, A. C. | de Freitas, L. M. M. | Lott, W. L.
Greenhouse studies indicated many soils of the central plateau of Brazil to have a poor S supply. The most acute deficiency was found on soil from an upland savanna, but surface soils (0 to 20 cm. A₀ excluded) from virgin forests also responded. The B horizon of cultivated soils responded less frequently than that of the virgin soils, suggesting some downward movement of S under cropping. Such movement was also indicated by higher levels of NH₄OAc-extractable S. Sulfur extracted in this way correlated well with growth responses of millet grown in pot culture. In most soils, the addition of 20 pounds S as CaSO₄ per 2 million pounds of soil resulted in maximum dry matter production under the intensive cropping existing in these experiments. It is postulated that responses to S in this region will not be common unless N and P levels are improved. If these elements are plentifully supplied, however, and cropping is intensive, S deficiencies may occur on many soils.
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