“…In New Zealand, Edmeades et al [22], having shown that the biological optimal pH for pasture is 5.8 to 6.0, used data from field trials to determine the amount of lime required to achieve pH 6.0-the field lime requirement, or to use Black's concept, the biological lime requirement. Slattery and Coventry [23] adopted a similar approach in Australia for a range of crops and soils, defining the lime requirement as the amount of lime to obtain 90% of maximum yield.…”