Lime and molybdenum in clover development on acid soils

Abstract

In a study of the factors concerned in the effect of lime on subterranean clover (Trifolium subterraneum L.) on an acid soil where nodulation is defective, it has been found that responses equal to those obtained with heavy dressings of lime can be obtained by the application of molybdenum together with only 2 cwt. of lime per acre at seeding. Marked response to molybdenum was obtained only where low levels of lime were used. Where heavier dressings of lime were applied the clover grew normally and did not then require treatment with molybdenum. Where no lime was used nodulation was defective and, during the first two )ears, response to molybdenum did not occur or was very small. Nodulation subsequently improved on the unlimed soil and response to molybdenum progressively increased over the five-year period of the experiments. In the year of sowing best results were obtained where the inoculated seed was drilled with the lime. The evidence suggests that defective nodulation of subterranean clover may be expected on new land where the soil reactions are less than pH 5.0, and that soils of higher pH but with minimum values less than pH 5.5 are also suspect. The importance of treatment with adequate superphosphate in addition to lime and molybdenum in the development of subterranean clover on this acid soil is stressed. The interpretation and significance of the positive and negative lime-molybdenum interactions obtained are discussed.