The responses of two genotypes of white clover to addition of lime to an acid permanent grassland soil

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Abstract
The response of white clover to addition of lime was studied in pots with an acid permanent grassland soil (pH 4.1), and a comparison made between a commercial cultivar (Blanca) and a white clover indigenous to the acid soil. The yield of both plants increased markedly with addition of lime, but the native genotype reached maximum yield at a lower pH. In both cases, however, only relatively small adjustments of pH were required to produce considerable increases in yield. The addition of lime reduced the amounts of Al and Mn extracted by 1M ammonium acetate and 0.01M CaCl2, and increased exchangeable Ca. It was suggested that, although plant contents of Mn were high and those of Ca low, the effect of lime was not on the clover plant per se but on nodulation and the supply of N through symbiotic fixation. When no lime was added, both plants contained concentrations of N below that suggested as critical, and had only limited numbers of nodules on their roots. Excess Al and/or Mn, or insufficient Ca may have been responsible for inhibition of nodulation at the low pH of the unlimed soil. Although the indigenous plant also grew poorly when no lime was added, it displayed a number of characteristics which may assist its performance and persistence under acid conditions in the field.