Establishment of lucerne with cover crops under different soil moisture conditions

Abstract The results of an irrigated and unirrigated trial in which lucerne was established in the spring with wheat, barley, peas, linseed, and maize cover crops are reported. All the cover crops were sown at two seed rates. Measurements were taken of soil moisture and shading beneath the cover crops, lucerne plant numbers and root weights, and lucerne herbage production in the first and second seasons. All the cover crops except the unirrigated maize reduced lucerne production in the first season, and where weeds were abundant the cover crops suppressed them significantly in the establishment season. The heavy sowing rates of the barley, linseed, and wheat cover crops reduced lucerne plant numbers on the irrigated trial but not on the unirrigated trial. The cover crops reduced lucerne root development. Marked differences in the shading effects of the cover crops were noted. Three postulations are made relating the effect of the cover crop on the lucerne to moisture conditions during the period of competition and to the shading effect of the cover crop.