ABSTRACT
In comparison with grasses, forage legumes generally have higher contents of protein, pectin, lignin, carotene and vitamins, but lower contents of water-soluble carbohydrates (WSC), cellulose and hemicellulose. Normally, grass grown in association with a legume which is fixing N will have a higher N, and therefore crude protein (CP), content than a grass sward, unless the grass sward is receiving a high rate of applied N fertilizer. Differences in concentrations of nutrient elements are often small, though legumes can have superior contents of some macronutrients (Ca, Mg) and micronutrients (Fe, Mn, Zn, Cu, Co, B, Mo, Se) (Whitehead, 2000). Soil nutrient supply and pH are influencing factors on nutrient concentrations, e.g. on K-rich soils, clovers have a higher K content than grasses, but the opposite occurs on K-deficient soils. There are also differences among legume species, with white clover usually having higher concentrations of most nutrient elements compared with alfalfa, red clover and sainfoin. Stage of growth has a strong influence on the nutrient concentrations of legumes generally, particularly in upright-growing species such as alfalfa and red clover in which the leaf: stem ratio decreases markedly with advancing maturity. However, in white clover, there is continued generation of new leaves and petioles from the stolon network, concurrent with advancing maturity of previously generated foliage, and this reduces compositional changes.
