Liming of Acid Soil: I-Effect on Plant Available Aluminium

Application of lime at the rates of 0,1120, 2240, 4480, 8960, 17920 and 35840 kg/ha on the soil of Qulin, Missouri, U.S.A., raised the soil pH from 4.4 to 7.3. The water-soluble aluminium in soil remained at a higher level within pHw 4.4 to 5.5. It was the least soluble in the range of pHw 5.5 to 6.5, and beyond 6.5 the concentration increased. Significant reduction in exchangeable and CaCl₂ extractable aluminium was observed due to the lime treatments and the concurrent rise in pH up to 4480 kg lime/ha. At 8960 kg lime/ha and above, associated with pHs greater than 5, both forms of aluminium remained unchanged and at a negligibly low level. The relations were best described by the equation; Y=aX^b. The plant aluminium content of corn, cotton, wheat and soybean was not affected appreciably, although significant reduction in exchangeable and CaCl₂ extractable soil aluminium was observed. The first increment of lime (1120 kg/ha) was the most effective in reducing the aluminium concentration in plants without further change with the higher treatments. Significant correlation coefficient between the soil and plant aluminium content of wheat suggested the sensitiveness of the crop to higher concentration of aluminium. The acquisition and the associated tolerance of the plants towards aluminium was in the order of corn>cotton=soybean>wheat.