A soil technological study on effectuating and maintaining adequate playing conditions of grass sports fields

<p/>Playing conditions of grass sports fields have been studied focusing on top layer soil strength meeting the requirements of usage. In a field investigation a reproducible soil strength criterion was found from firmness appraisals and simultaneous measurements of soil strength. From relationships between soil strength and soil water pressure head for differently composed and compacted sandy top layers, pressure head and bulk density values were derived that limit playing conditions. The incompatibility between top layer compaction required for adequate playing conditions and grass viability has been examined. The oxygen status of grass sports field soils was compared with oxygen diffusion rates and concentrations mentioned in literature to limit grass growth. To interpret the field measurements, oxygen distributions at different oxygen consumption rates for various combinations of top layer and subsoil as well as for different rooting depths were calculated. From laboratory investigations detailed information was obtained about compaction susceptibility of differently composed and wetted sands and about the contribution of texture, organic matter, pressure head, bulk density and grass roots to soil strength. To find out best top layer-subsoil-drainage combinations, model research was done. Taking steady-state conditions for soil water flow, the top layer thicknesses required to prevent ponding on differently permeable subsoils were derived. To illustrate the effects of type of top layer, subsoil and drainage on soil water conditions in the top layer, pressure head profiles have been calculated. The same effects have been studied by using an electronic analog that simulates the non-steady-state flow of water in soil. From the simulated course of the pressure head in the top layer, duration and frequency of inadequate playing conditions have been established with the aid of pressure head and density limits obtained from the field and laboratory measurements. Finally, a number of conclusions and recommendations to effectuate and maintain adequate playing conditions of grass sports fields are given.