A study of mole drainage with simplified cultivation for autumn-sown crops on a clay soil. 4. A comparison of direct drilling and mouldboard ploughing on drained and undrained land on root and shoot growth, nutrient uptake and yield

Abstract

Cereal crops were grown after direct drilling or ploughing on an undrained or drained clay soil over 4 years to examine whether crop growth after different methods of tillage is influenced by the intesiity of drainage. Winter cereals were grown in each year, wheat for 3 years and oats in the remaining year. In 3 of the years (years 1–3) the total annual precipitation was close to the long-term mean, and the mean depths of the water table during the winter in the undrained and drained land were about 20 and 40 cm, respectively. In the 3rd year, an unusually wet autumn also caused very wet topsoil at sowing time, which persisted throughout the winter. The 4th year was much drier than average, and the water tables remained below drain depth. An interaction between the intensity of drainage and the method of tillage occurred only in the 3rd year, with the wet autumn, when completion of ploughing, seed-bed preparation and sowing of the oats were delayed. This disadvantaged the direct-drilled crop on the undrained land, where seedlings experienced pre-emergence waterlogging so that the plant population was 20 m −2 and yield was only 55% of the crop grown after ploughing; on drained land, there was little difference in establishment or yield between the tillage treatments. Drainage did not affect yield in the 2 drier years, the 1st and 4th, and in the latter year the grain yield of winter wheat was 11.5 t ha −1. In the 2nd year, drainage increased yield by about a quarter, when root growth and nutrient uptake were restricted on the undrained treatment. Averaged over the whole duration of this experiment, 4 years reported here and 2 years already published, the mean increase in grain yield of winter cereals due to drainage was 13% (0.9 t ha −1). On average, the 3 direct-drilled winter wheat crops yielded 4% more grain than crops grown on ploughed land due to an advantage in one year. Root extension in winter was slightly faster after direct drilling than after ploughing, but the difference subsequently diminished or disappeared.