Impact of soil management systems on soil structure and physical properties in a clay loam soil, and the simulated effects on water deficits, soil aeration and workability

Abstract

The effects of different soil management systems on soil structure and associated physical properties in a Dutch clay loam soil were evaluated using a combination of simulation modelling, field investigations and laboratory experiments. The investigations were focused on field recognition of identical soils only differing in structure type caused by soil management systems. Two soil structure types were recognised: a type developed in permanent grassland and a type in young arable land, which had been used for intensive vegetable growing since 1979. The types were characterised by examining the micro- and macro-morphology and soil hydraulic properties, such as soil structure, rooting patterns, pore shape and size distribution, bypass flow and water retention and unsaturated hydraulic conductivity characteristics. Field recognition of structure types and subsequent morphological and physical characterisation was used as an alternative to the application of a machine-soil submodel. Significantly different properties of both soil structure types were functionally interpreted by using a simulation model for the soil-plant subsystem. Morphological and hydraulic analyses were essential for the definition of proper boundary conditions and input parameters. The land qualities water deficits, workability and soil aeration were calculated for a potato crop under Dutch climatological conditions. Expressions for temporal variability were obtained by using a 30 year record of weather data. The soil structure of permanent grassland proved to be more favourable than that of young arable land. This resulted in a 10% decrease in the average annual water deficit, 40% more workable days in the planting phase and 5–10% more days with a well-aerated soil. The impact of these differences on the potato tuber yield interpreted in terms of the effect of soil structure degradation, was estimated to be at least 5% in 20 out of 100 years under Dutch climatic conditions. The differences calculated also equalled the maximum possible effect of soil structure regeneration.