WATER-RETENTION IN ROOT-ZONE SOIL MIXTURES OF LAYERED PROFILES USED FOR SPORTS TURF

Where coarse-textured materials, such as gravel, underlie the root-zon e layer of sports turf soil profiles, mater retention in the root-zone layer is increased. The objective of this research was to determine t he water retention characteristics in sand and sand : peat mixtures pl aced over coarse-textured layers and to determine how sand particle si ze and type of peat in the mixtures influenced water distribution afte r drainage. Soil profiles consisted of 30 cm of sand or sand : peat mi xtures over 5 cm of predominantly coarse and very coarse sand, which i n turn was over 10 cm of gravel. Excess water was added to the profile and allowed to drain for 24 or 48 h, following which water content an d air-filled porosity (AFP) in the mixtures were evaluated. Regardless of the root-zone mixture, the coarse-textured sublayers resulted in a wet zone in the lower portion of the root-zone mixture. An unamended, predominantly medium and coarse sand, when used in the 30-cm root-zon e layer, maintained approximate to 10% AFP in the lower 6 cm after dra inage. Sand : peat mixtures using this sand generally maintained 3% to 8% AFP in the lower 12 cm of the root-zone layer. An unamended, predo minantly fine and medium sand root-zone layer had approximate to 6% AF P in the lower 9 cm and sand : peat mixtures using this sand had <5% A FP in the lower 12 to 18 cm of the root-zone layer, with significant p ortions remaining at or near saturation after 24 or 48 h of drainage.