Effects of lime on yields and phosphate uptake by clover in relation to changes in soil phosphate and related characteristics

Abstract

In a glasshouse experiment on 15 acid soils from north-eastern New South Wales, lime was applied in factorial combination with phosphate to determine their effects and interactions on the yield and phosphorus uptake of white clover. Phosphate caused significant yield responses on all but one soil. The higher rate of lime increased the uptake of soil phosphate, but decreased the apparent uptake of fertilizer phosphate from most soils. These effects were generally consistent with lime-induced increases in phosphate concentration in the soil solution, exchangeable phosphate and buffer capacity. The effects of lime on yields and phosphorus uptake by clover on the 14 phosphate-deficient soils suggest that responses to lime will depend on whether the soils are high in manganese or toxic in aluminium. Where clover contained > 110 ppm manganese, lime increased yields only in the absence of applied phosphate (negative interactions). Where clover contained toxic levels of aluminium, lime increased yields only in the presence of phosphate (positive interaction). In the former soils, lime increased the levels of exchangeable phosphate, phosphate concentration in solution, and uptake of soil phosphate, but generally depressed the uptake of fertilizer phosphate. In the aluminium toxic soil, lime greatly decreased the levels of exchangeable phosphate and buffer capacity, and increased the uptake of fertilizer phosphate but not of soil phosphate.