RESPONSE OF CUT GRASS TO POTASSIUM AND TO THE MINERAL SYLVINITE

An experiment was carried out at five sites in England and Wales to investigate the effect of applying potassium (K) at 0, 31 and 62 kg ha−1 in all combinations with sodium (Na) at 0, 20 and 40 kg ha−1. The nutrients in the form of chlorides were applied to perennial ryegrass swards for each of several cuts per year for up to four years. Additional plots received Sylvinite, a naturally occurring mixture of potassium and sodium chloride, at 120 and 240 kg ha−1. At three sites significant (P<0.05) yield increases due to K and Sylvinite applications were measured when ‘available’ soil K fell below 100 mg litre−1 and the K content of herbage from the control plot was 1.2% of dry matter. At two sites in the absence of applied K there were significant (P<0.05) yield responses to Na. In all aspects Sylvinite behaved similarly to mixtures of the two salts at the appropriate levels of application. Copyright © 1990 John Wiley & Sons, Ltd