Studies on Response of Legumes to Molybdenum and Lime Fertilization on Mardin Silt Loam Soil

Greenhouse experiments were conducted on Mardin silt loam to determine the response of alfalfa, birdsfoot trefoil, ladino and red clover to Mo applied alone and in combination with different increments of lime and P. Two strains of birdsfoot trefoil Rhizobium were also compared for differences in response to Mo and lime. These treatments were evaluated in terms of dry matter production and content of total N and Mo in forage and roots. The effect of these treatments on nodulation was studied with birdsfoot trefoil. All legumes responded to Mo as shown by increases in yield and N content of forage and roots. Birdsfoot trefoil showed the greatest response to Mo. An interaction between Mo and lime was found for alfalfa, birdsfoot trefoil and ladino clover. Mo applied with lime at rates less than 2 tons per acre increased the yield and N content of the forage. However, at 2 tons of lime per acre or greater there was no response to the addition of Mo. A direct relationship existed between soil pH and Mo content of the forage of birdsfoot trefoil. Four to five tenths ppm. Mo in the forage was found to be adequate for maximum growth. Molybdenum increased the size of individual nodules and reduced the total number of nodules on birdsfoot trefoil plants. A correlation existed between the number of nodules per plant and the N content of the forage. The strain of Rhizobium or level of P did not affect yields or N content of forage or roots. Yields from treatments that received 2 tons of lime per acre were always greater than those receiving less lime, whether or not Mo was added. Yield and N data suggest that when lime was applied at a rate of 2 tons per acre or greater it had an additional effect besides increasing the availability of Mo, P, or providing a suitable environment for Rhizobia bacteria. This was especially pronounced in alfalfa and to a lesser degree with birdsfoot trefoil and the clovers. A possible reason for this is given in the discussion.