Essentiality of Molybdenum for Alfalfa on Highly Oxidized Piedmont Soils1

Abstract

AbstractProduction of alfalfa (Medicago sativa L.) has steadily declined on highly oxidized soils of the Southeast during the past decade. An investigation was conducted to determine if lack of Mo is responsible and if lime or N replaces the Mo requirement of alfalfa and if there are other alternatives such as use of CaSO4 and Mo to replace lime, MgCO3 substitution for CaCO3, and if high initial lime applications may replace lesser annual applications. Field investigations using two highly oxidized Udults revealed that neither N at 67 kg/ha, nor lime at initial rate of 11,200 kg/ha or annual applications of 2,240 kg/ha replaced the Mo requirement of alfalfa. Nitrogen increased crabgrass (Digitaria sp.) competition, which resulted in less alfalfa forage. Calcium from CaSO4 with or without Mo did not maintain alfalfa. MgCO3 and CaCO3 applied at equivalent rates were equally effective as liming materials. An initial lime treatment of 11,200 kg/ha produced yields equal to that obtained by annual application of the same total amount of lime over a 5‐year period.