Molybdenum Concentration of Certain Crop Species as Influenced by Previous Applications of Molybdenum Fertilizer¹

Abstract

Abstract Excessive Mo concentrations in forage crops have been reported to cause toxicity in livestock. Since forage crops often are grown following crops fertilized with Mo, a study was conducted to determine the effect of previous applications of Mo on Mo concentration and yield of dry matter of certain crop species. Five different crops were grown on Maury (Typic Paleudult; clayey, mixed, mesic) soil (pH 6.4) fertilized the previous year with levels of Mo (0, 0.22, 0.44, 0.88, 1.32, and 2.64 kg Mo/ha). The above‐ground plant parts were sampled at one or more dates, weighed, dried, and ground for Mo analysis. Generally, concentration of Mo increased as the level of Mo applied previously increased in all crops sampled and at most sampling dates. For crops sampled at two maturity dates, Mo concentrations were higher in plants sampled at the earlier date than when plants were mature. The lower values at mature harvest may be attributed to dilution by dry matter. Although concentrations increased with level of Mo applied, the highest concentration found (3.89 μ g Mo/g dry weight) was judged unlikely to cause toxicity in livestock. Mo fertilization at recommended rates of soils with low‐to‐average Mo levels should not subsequently result in forage with Mo concentrations that are toxic to livestock. Mo fertilization had little effect on dry matter yields.