| abstract |
A level unobstructed grass sports and recreation surface wherein the grass is deeply rooted in a layer of sand overlying a layer of gravel and preferably nurtured from below to provide a controlled growing environment exhibiting vigorous growth. The sand has more positive vertical liquid flow characteristics whereas the gravel has better horizontal liquid flow characteristics and the appropriate gradation selection of both determines the high drainage ability and uniform fertilizer/irrigation distribution throughout the system. The grass surface is defined by a water tight membrane extending from the perimeter, adjacent the surface and completely underlying the gravel layer. Control means are provided to detect the liquid level contained within the membrane and add or remove liquid to maintain the appropriate level. The buried conduit system is used for the controlled addition of water/fertilizer and excess drainage removal. The nutrified liquid from the reservoir is hydroponically supplied to the roots of the grass on a continuous demand basis. Heating cable may be placed at the boundary zone on top of the gravel and sand layers to warm the sand to remove frost and melt snow. An insulation layer may be placed beneath the membrane to minimize frost penetration to the subgrade. The system may be either completely automatic and programmed to accommodate external conditions such as degrees of use of the field, climatic conditions or the like or alternatively may be partially automatic and supported by more standard methods. Coupled with the control system can be a sensing unit to determine automatically the nature of the contained liquid. |