CONCENTRATIONS OF N, P, K, CA, MG AND NA IN PERENNIAL RYEGRASS AND WHITE CLOVER LEAVES OF DIFFERENT AGES

Leaf blades of perennial ryegrass (Lolium perenne) at five development al stages, from unemerged to dead, were collected from cut swards grow n under field conditions. Similarly, leaflets of white clover (Trifoli um repens) at four developmental stages, from tightly folded to proxim al to the youngest fully developed leaf, were collected. The leaves we re analysed for N, P, K, Ca, Mg and Na. In perennial ryegrass, the con centration of N declined by about half and those of P and K declined b y about two-thirds, as leaves aged. By contrast, the concentration of Ca increased more than five-fold and that of Mg about twofold as leave s aged. The concentration of Na initially increased more than twofold but then declined as leaves died. In white clover the concentration of N declined by about 20% as leaves aged, while the concentrations of P and K declined by about 50%; the concentration of Ca increased about fivefold, that of Mg declined by about 15% and that of Na increased by about 15%. The application of N increased the concentrations of N and K in ryegrass leaf blades at all stages of development. The applicati on of P increased the concentrations of P and Na in the leaves of both species.