EFFECTS OF SIMPLIFIED CULTIVATION ON THE GROWTH AND YIELD OF SPRING BARLEY ON A SANDY LOAM SOIL .1. SHOOT GROWTH AND GRAIN-YIELD - RESPONSE TO NITROGEN

Two experiments, each of three years duration (1975-1977 and 1978-1980), were carried out on a sandy loam soil to investigate the effects of mouldboard ploughing, shallow tine cultivation and direct drilling on the growth and yield of spring barley receiving different rates of application of nitrogenous fertilizer. Grain yields of the ploughed and shallow-cultivated treatments were similar (approximately 6 t ha-1) provided optimum amounts of nitrogenous fertilizer were applied, but direct drilling reduced yield, on average by 23% at 30-35 kg nitrogen (N) ha-1 and by 12% at 115-150 kg N ha-1. The direct cause of the reduction in grain yield after direct drilling compared with ploughing was a lower number of ears, except in 1977 when the difference was due to a smaller number of grains per ear and a lower thousand-grain weight. In the absence of nitrogenous fertilizer, less N was taken up by direct-drilled barley during its growth than by barley grown after ploughing or shallow tine cultivation, and there was still a difference at the highest level of fertilizer applied. The most profitable rates of N application were calculated for each cultivation system from fitted quadratic equations. These optimum rates were similar for all cultivation treatments in the final year of the first experiment (approximately 120 kg N ha-1), and were similar for direct drilling and ploughing in the second experiment (approximately 130 kg N ha-1), whereas the optimum for shallow cultivation was 185 kg N ha-1. At prevailing grain and fertilizer prices, the margin over fertilizer costs was between Pound 73 and Pound 87 ha-1 less from direct drilling than from ploughing or shallow tine cultivation.