Investigation of soil amendments for use in golf course putting green construction

Turfgrass, like all livings organisms, requires water for survival. Turfgrass professionals have a limited amount of water they can use due to consumptive use permits levied by local municipalities. Therefore, they are required to find alternate means of maintaining quality turf while using less water. Many turf professionals use soil amendments because of their ability to increase moisture and nutrient availability. However, whether or not soil amendments actually influence the efficient use of water by turfgrass is not known. An objective of this research was to determine the influence of soil amendments and incorporation method of those amendments on water-use-efficiency (WUE) of Tifdwarf bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy]. A further objective was to determine the influence of surfactant-modified soil amendments (SMSAs) on nitrogen (N) and phosphorus (P) leaching. To determine the influence of amendments on turfgrass WUE, Tifdwarf bermudagrass was established on pots in a glasshouse at the University of Florida Turfgrass Envirotron. Treatments consisted of sand, two zeolites, two calcined clays (CCs), two diatomaceous earths, Canadian sphagnum peat, iron humate, and a smectite. Treatments were arranged in a randomized complete block design. Pots were weighed, harvested, and rated weekly for turf quality for twelve weeks. To determine the influence of SMSAs on N and P leaching, soil columns were fabricated from 2.54 cm diam. tubes. Each column was packed with a rootzone layer (30 cm) consisting of sand/peat (85:15) and a filter zone layer (5 cm) containing each treatment. Treatments were sand, zeolite, and two CCs. Treatments either remained unchanged or were surfactant-coated. Incorporation of iron humate increased turf yield, quality, and WUE above all other amendments. This was attributed to an increase in nitrogen and iron as well as a 13% increase in plant available water. Rootzone amended with CCs produced 40% more dry matter yield and increased WUE 30% above sand/peat. However, calcined clays did not produce quality or WE ratings above iron humate. Sand and zeolite produced quality and WUE ratings equal to that of sand/peat mixtures. Of the amendment investigated in this study, only iron humate and CCs consistently produced quality and WUE ratings above that of sand/peat rootzones. Incorporation of amendments following aerification reduced each amendment's influence on yield, quality, and WUE. Therefore, in order to maximize amendment influences on turf quality and WUE, amendment should be fully incorporated into the rootzone. Surfactant-modified amendments reduced NO3 levels in leachate to as low as 0.0%, reduced NH 4 to as little as 4%, and reduced P levels to as little as 3% of that applied. Unmodified amendments had no influence on NO3 leached, reduced NH4 leaching, and retarded P leaching. Surfactant-modified amendments may be a plausible option to reduce N and P leaching in USGA putting greens.