Long‐term studies of molybdenum applied to pasture

The effects on pasture of single and repeated applications of 0, ¾1½, and 3 tons/ac of ground limestone with and without 2½ oz/ac of sodium molybdate were studied over an eight‐year period. Molybdenum alone gave a marked response which remained effective for seven years. Three tons of lime gave a similar yield and proved effective for five to seven years. The response from lime was slower than from molybdenum. In the presence of molybdenum there was no response from lime. Initial responses were in the white clover ( Trifolium repens L.) and subsequently in the sown grasses. From the fifth year white clover yields in the molybdenum alone treatment fell off relative to the lime treatments. Mixed herbage Mo levels were increased by the application of lime or molybdenum, but appeared a poor guide to requirement. The highest level attained in the trial was 3.3 p.p.m., well below that associated with stock ill‐health. The optimum pH in the absence of molybdenum was 6.6, in the presence of molybdenum 5.7 or less. The effect of treatments on the molybdenum sta tus of the soil was apparent using Grigg's method of extraction. Heavy liming accelerated downward movement of Mo.