INFLUENCE DU DALAPON ET DES ELEMENTS N, P, K SUR LA GERMINATION ET LE DEBUT DE LA CROISSANCE DE TROIS LEGUMINEUSES FOURRAGERES (LOTUS CORNICULATUS, MEDICAGO SATIVA ET TRIFOLIUM REPENS)

Abstract

Germination tests were conducted with alfalfa, ladino clover and birdsfoot trefoil in order to determine the effects of dalapon, nitrogen, phosphorus and potassium on the germination of the three legumes. Seeds were germinated on wet blotting paper. The herbicide, N, P and K were used at the following rates: dalapon, 0 and 5 kg/ha active ingredient; N, 0. 20, 40 kg/ha; P, 0, 17.5, 35 kg/ha; K, 0, 16.5 and 33 kg/ha. In a second experiment, the herbicide and chemical fertilizers, used at the same rates as in the first experiment, were mixed with seeds and seeded on a Coaticook silt loam under greenhouse conditions in order to measure their effects on the establishment and growth of the legumes. In the Petri dishes, phosphorus had the greatest effect. Phosphorus reduced germination by 97%, nitrogen by 71%, potassium by 65% and dalapon by 26%. Germination of alfalfa was less affected by the treatments than the germination of the other two legumes. Under greenhouse conditions, where legumes were grown in soils, the effects of treatments were less deleterious than on wet blotting paper. Number of alfalfa and ladino clover plants per pot was reduced and the yields were decreased by 37 and 54%, respectively, for the two legumes. Dry matter yields of alfalfa were increased by phosphorus mixed with nitrogen. Potassium decreased the number of legume plants per pot. Number of nodules on the legume roots was also reduced by potassium application.