The residual effect of molybdenum fertilizer on growth of tropical pasture legumes in a sub-tropical environment

Abstract

The response of several tropical legumes, grown with Panicum maximum cv. Gatton, to an initial application of molybdenum as molybdenum trioxide was studied over a five year period at six sites in south-eastern Queensland. The most responsive legumes were Glycine wightii cv. Tinaroo and Desmodium intortum cv. Greenleaf, followed by Macroptilium atropurpureum cv. Siratro and Medicago sativa cv. Hunter River, with Lotononis bainesiicv. Miles and Stylosanthesguianensis cv. Cook being least responsive. Sites differed markedly in magnitude of legume response. For example, the most responsive site required 200 g ha-1 molybdenum over five years for maximum growth of Siratro whereas there was no response of Siratro to molybdenum application at another site. There was no difference between surface-applied molybdenum trioxide, molybdenum trioxide applied to the seed pellet and surface-applied sodium molybdate in their residual effects on legume growth. Response of the grass to molybdenum treatment was generally similar to legume response and nitrogen concentrations in legume and grass increased with yield.