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Use of lime and of ordinary superphosphate for cotton cultivated on acid clay soil

Results of a four year liming experiment with cotton are discussed. This experiment was conducted on Latosolic B Terra Roxa soil, acid, with a pH index of 5.0, originally under "cerradão" vegetation, with 66% of clay, 4.3% of organic mater, 0.9, 0.8 and 0.5 (meq/100 ml) of Al3+, Ca2+and Mg2+, respectively. The experimental design was a split-plot, with four replications. Dolomitic limestone was applied in the first year, on main plots at the levels of 0, 1.5, 3.0 and 6.0 t/ha. P and K were annually applied on split-plots, as a factorial 3 x 2, at the levels of 0, 60 and 120 kg/ha of P2O5, and 40 and 80 kg/ha of K2O, respectively, with ordinary superphosphate and potassium chloride. Four months after lime application, the neutralization of the exchangeable aluminum found by soil analysis was observed, at the highest level, the pH value increased up to 5.5 and values of calcium plus magnesium reached 3.0 meq. The linear effect upon cotton yield, due to liming, was significant during all the period of this study, increasing from the first to the third year. The effect of phosphorus was smaller, but positive and significant. Cotton plants did not react to potassium fertilization and interactions were not observed. Lime increased the concentrations of P, Ca and Mg in leaf blades, and decreased those of K, Fe, Mn and Al in the year when it was applied. There were no symptoms of K or micronutrient deficiencies due to the use of lime at high level.


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