Use of simulation to assess the effects of different tillage practices on land qualities of a sandy loam soil

Four different soil-structure types could reproducibly be recognized by soil surveyors working on Dutch sandy loam soils with different management practices. The 4 structure types were soils with a primary ploughpan, a loosened ploughpan, a secondary ploughpan and a grassland structure. These types had significantly different soil-physical properties and rooting depths. Soil-water regimes for a 30-year period were stimulated to obtain quantitative information on the influence of soil structure, as an expression of different soil-management practices, on land qualities such as moisture deficit, aeration status and workability.These land qualities were not significantly different for the 3 structure types of arable land when considering the entire soil profile. However, differences in moisture content and aeration status were significant when undisturbed and disturbed ploughpans were compared. Deep ploughing to disrupt the primary ploughpan should therefore not be encouraged in these soil as long as common field operations remain unchanged. The same land qualities for grassland indicated what may be attained by soil-structure regeneration. The probability of having a workable day in spring or autumn is increased by an estimated 20%, and the number of days with adequate aeration by 10%, in soil-structure types of arable land (A, B and C) as compared with grassland soil structure (D). Moisture deficits in the growing season should be about 50% less.In this study, simulation was not used to simulate soil-structure formation as a function of soil management, but soil structure was used as an input for the models, reflecting different management practices. To that end, the various structure types were characterized by physical measurements.