EFFECT OF DEPTH OF LIME INCORPORATION ON THE GROWTH OF CORN ON AN OXISOL OF CENTRAL BRAZIL

High Al saturation is one of the limiting factors to intensive cropping of many soils in the Cerrado of Brazil. A field study on the effect of lime rate and depth of incorporation on growth of corn (Zea mays L.) was conducted on an Oxisol (Typic Haplustox) at Brasilia. Lime rates used were 0, 1, 2, 4 and 8 tons CaCO3/ha and depths of incorporation were 15 and 30 cm. Incorporation of 4 tons of CaCO3 to a depth of 30 cm reduced Al saturation from 72% to < 5% on a soil which initially had 1.1 meq Al/100 cm3. Concentrations of soil solution Al decreased to very low levels at pH 5.5. Grain yields of 3 successive corn crops were increased by liming. Incorporation of lime to a depth of 30 cm resulted in higher yields than incorporation to a depth of 15 cm. Application of MgSO4 to the acid soil increased yields above the nonlimed treatment. Yield responses to liming were due to improved Mg nutrition and neutralization of toxic Al. Root length was increased considerably in the 0-15 cm depth and doubled in the 15-30 cm depth when Al was neutralized by liming. Increased root development in the 15-30 cm depth of the deep lime treatments resulted in greater water utilization from this depth and decreased the detrimental effects of moisture stress at tasseling on corn yields.