MAGNESIUM DEFICIENCY IN LUCERNE

Abstract

An experiment was conducted on lucerne (cv. Wairau), growing on a yellow-brown pumice soil low in magnesium. Under a regime of four harvests annually, small but sign&cant yield responses of 4 and 5% were obtained in the third year to additions of 17 and 34 kg/ha Mg, respectively, when the topsoil (0 to 7.5 cm) Mg value in the control plots had fallen to 2 units (advisory scale). Responses were associated with a concentration of 0.09% Mg in herbage cut ,at the onset of flowering. Foliar symptoms of magnesium deficiency were a chlorosis which increased in severity towards the base of the plant.