Liming and Cultivars Affect Root Growth, Nodulation, Leaf to Stem Ratio, Herbage Yield, and Elemental Composition of Alfalfa on an Acid Soil.

Soil acidity is one of the limiting factors affecting the production and sustainability of pastures and crops in many parts of the world. An on-farm experiment was conducted in Australia to investigate the cultivar variation in alfalfa (lucerne) (Medicago sativa L.) with respect to soil acidity and response to applied lime. The experimental site was a brown sandy clay loam with a soil pH of 4.8 (1:5 calcium chloride). Ten cultivars (Hunter River, Hunterfield, Sceptre, Aurora, Genesis, Aquarius, Venus, PL90, PL55, and breeding line Y8804) were tested at two levels of lime (0 and 2 t ha-1). Lime application significantly increased the root growth, nodulation, leaf retention, leaf to stem ratio, herbage yield, and crude protein content of alfalfa. Liming had a significant effect on elemental composition of alfalfa shoots. Aluminum (Al) concentration was reduced from 93 mg kg-1 DM in nil lime treatment to 45 mg kg-1 DM in +lime treatment. Similarly, manganese (Mn) and iron (Fe) shoot concentrations were reduced from 74 mg kg-1 DM and 92 mg kg-1 DM to 59 mg kg-1 DM and 76 mg kg-1 DM, respectively. Liming significantly improved the calcium (Ca) concentration of shoots, while there was a little effect on phosphorus (P) and zinc (Zn) concentrations of alfalfa shoots. Cultivars had differential response to lime application. Response to lime application was greater in Y8804 and Aurora alfalfa where yield increased by 32% and 31%, while yield increase was 11–22% in other cultivars. Cultivars also differed significantly in root growth, nodulation, leaf drop, leaf to stem ratio, crude protein content, and elemental composition of shoots. Cultivars with better performance in no liming treatment had comparatively lower shoot Al, Mn, and Fe concentrations compared with other cultivars. [ABSTRACT FROM AUTHOR]