Potassium‐sparing effect of calcium in perennial ryegrass

Perennial ryegrass in soil culture was treated with different rates of potassium fertilizer and calcium carbonate, to determine if calcium could substitute for potassium in plant shoot tissue without interfering with dry matter production. By increasing the concentration of calcium in plant shoots to approximately 0.8% in the dry matter, the critical potassium concentration was decreased to 0.6%. This critical potassium concentration was probably the minimum concentration necessary to maintain essential potassium‐specific metabolic processes in perennial ryegrass shoots.