| Modern golf course putting greens are constructed using sand because it resists compaction, drains quickly and maintains air-filled pore space even under heavy use. Traditionally, peat moss is added to sand to increase water retention, but is subject to decay which may negatively affect physical properties. Therefore, alternative materials such as inorganic amendments (IA's) that offer similar benefits but are not be subject to decay may be desirable. Most putting greens are planted to the cool-season turfgrass species, creeping bentgrass (Agrostis stolonifera var. palustris Huds. Farw.), which frequently declines in extended hot, humid, conditions possibly due to low soil oxygen contents, excessive soil wetness, high temperature stress, or several turfgrass diseases. A laboratory study evaluated several IA's and sphagnum peat moss for their effect on the physical properties and nitrogen leaching of sand mixtures. A field study evaluated rootzone mixtures for their effect on bentgrass establishment, growth, and soil microbial dynamics. Additionally a mechanical forced air blower/vacuum technology was investigated for its ability to manipulate rootzone temperature, water and gas contents, and perhaps ultimately to improve the summer survival of bentgrass. Amendments had significant effects on all physical properties with sands amended with IA's or peat moss resulting in lower bulk densities, generally higher water retention, and highly variable saturated hydraulic conductivity. Compared to peat moss, the IA's were not as effective at increasing water retention to recommended levels. Nitrogen leaching in sand amended with peat moss or two of the IA's was significantly lower than unamended sand, primarily due to ammonium retention. The mechanical blower/vacuum had very little effect on water or gas contents, rootzone temperature, visual turfgrass quality and rooting. Supra-optimal rootzone temperatures during summer months appeared to be the key environmental factor affecting the decline of bentgrass rootmass, rather than soil physical properties. Lastly, microorganisms reached large, >107, populations and become relatively stable within the first year of establishment regardless of rootzone composition. |
