SOLUTION CONCENTRATIONS REQUIRED FOR NEAR MAXIMUM YIELD IN RYEGRASS AND WHITE CLOVER WHEN GROWN IN A LOW IONIC-STRENGTH SOLUTION - PRELIMINARY-RESULTS

In a series of preliminary experiments, the effect of varying solution concentrations of several nutrients on yield in ryegrass (Lolium pere nne L. cv Grasslands Nui) or white clover (Trifolium repens cv Grassla nds Huia) were investigated using a still low ionic strength (2.7 x 10 (-3)M) nutrient solution culture technique. The concentration of the n utrients in the basal solution was (mu M): 500 calcium (Ca); 100 magne sium (Mg); 300 potassium (K); 600 nitrogen (N) [150 ammonium (NH4), 45 0 nitrate (NO3)]; 2.5 phosphorus (P); 600 sulfur (S); 3 boron (B); 2.5 iron (Fe); 0.5 zinc (Zn); 0.5 manganese (Mn), and 0.1 copper (Cu) at pH 4.7. The solution concentrations required for 95% maximum yield in ryegrass (mu M) were: < 240 for total N, 2 for P, < 240 for S, < 40 fo r Mg, < 200 for Ca, and < 100 for K. The < symbol indicates that yield did not decrease nor increase, suggesting that the lowest solution co ncentration used (shown after < Symbol) was adequate for 95% maximum y ield. In white clover, solution concentrations required for 95% maximu m yield (mu M) were: < 38 for NH4, 10 for P,< 150 for S, 150 for Mg, < 125 for Ca, and 300 for K. Yield also declined for white clover when additional trace nutrients [Mn, Zn, Cu, iron (Fe), and boron (B)] were added, although the trace nutrient that was toxic could not be determ ined.