AbstractThe effects of lime applied at 20, 40, and 60 cm depth, and of calcium nitrate applied in the top 20 cm, in terms of yield of two corn hybrids and on soil acidity factors in Humatas clay (a typical upland Ultisol of Puerto Rico) were determined. The first corn crop (Funk's G-795 W) revealed a significant linear relationship between corn yield and soil pH and exchangeable bases of the top 60 cm. The second crop (G-795 W), the dry stover yield of which was used as a criterion to evaluate treatments, did not reveal significant effects of soil acidity factors on yield. The third crop (Pioneer X-306 B hybrid) showed a highly significant quadratic effect of pH and soil acidity factors of the 0-60 cm zone on corn yield. The fourth crop (X-306 B) revealed a highly significant linear effect of pH and soil acidity factors on yield. The application of calcium nitrate resulted in low yields approximating those of the unlimed treatments. The inactivation of ionic aluminum , particu larly at lower soi l depths, with concomitant improvement in root development and moisture uptake is considered the main reason for higher yields.
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