Experiences with deep tillage in the Netherlands

Abstract

A review is given of a national symposium on deep tillage, which was held in December 1984 at Wageningen, The Netherlands. By nature, in sandy loam soils (8–17% clay) with a low organic matter content, and in sand soils without organic matter, the subsoil may be so dense that root development is unsatisfactory, crops suffer from drought and yields are reduced. Ploughpans are common in all Dutch soil types. Light soils (< 17% clay) do not crack on drying and here, ploughpans may hamper root growth and transport of water and gases. This negatively affects emergence, crop development and the number of work days in autumn and in spring. Deep tillage by subsoiling, rotadigging or rotamixing has a pronounced effect on total porosity and macroporosity, but usually recompaction starts very quickly and after 2–3 years, throughout the loosened layer, bulk density may be higher and macroporosity lower than before deep tillage. To conserve the loosening effect of deep tillage, field traffic and tillage systems should be modified and, preferably, deep rooting crops with a long growing period (alfalfa, seed grass) should be grown. Deep tillage should never be performed to a greater depth than the bottom of the compact layer. In view of the high costs of deep tillage, it is advisable to consider alternatives, such as tile drainage to improve emergence and to increase the number of work days, and sprinkler irrigation to improve crop development and yield.