Cultivation and nitrogen requirements for drilled and broadcast winter barley on a surface water gley (Gleysol)

Abstract

Direct drilling, seed broadcasting plus rotovation, rotovation plus drilling and shallow mouldboard ploughing plus drilling were examined as possible quick and cheap alternatives to conventional mouldboard ploughing. The experiment ran for four seasons during 1980–1984. In the first season nitrogen was top-dressed at a uniform rate slightly greater than recommended, but in the final three seasons, dressings were either at the recommended rate or at 40% greater than the recommended rate. The topsoil (0–300 mm depth) of the experimental site was a sandy clay loam containing 4% w/w easily oxidisable organic matter overlying a slowly permeable subsoil. The experimental site was situated in south-east Scotland. In the first season, the non-ploughing treatments yielded less than conventional ploughing treatments because wet weather prevented adequate chemical weed control. In the remaining three seasons direct-drilling and broadcasting plus rotovation yielded, on average, 6% more grain than the normal ploughed and rotovated plus drilled treatments. Total root lengths were least in the direct-drilled and broadcast treatments and plant populations were independent of treatment. In the broadcast and direct-drilled treatments, P and K and organic matter were concentrated in the surface layer as were most of the roots. Of the non-ploughing treatments, the direct-drilled soil was the most compact. The broadcast seedbed was the least compact because there was no traffic after the soil was cultivated to incorporate the seed. Direct-drilled soil was suspected to have the most stable structure because it contained most organic matter, particularly at the surface. Weed control, timing of operations and control of traffic were critical to the success of direct drilling. Since adverse weather conditions may prevent the attainment of such a high standard of management, the recommended minimum cultivation requirement is ploughing to > 150 mm depth. Increasing the nitrogen rate to 40% above that recommended gave an economically worthwhile 0.6 t ha −1 increase in grain yield.