Maturation of Amended Sand Root Zones Over Seven Years.
James Devaney, Hiranthi Samaranayake, T.J. Lawson, and James A. Murphy. Rutgers University, 59 Dudley Rd. Foran Hall., New Brunswick, NJ 08901, United States of America
Sand-based root zones are commonly used to construct golf course putting greens; however these are reputed to develop undesirable physical properties over time. This field study investigated the potential changes in physical properties of sand-based root zones over a seven year period. Eight sand-based root zone mixtures varying in amendment (peat, inorganic and loam) were replicated four times in a randomized complete block design located in two microenvironments. Plots were seeded to ‘L-93’ creeping bentgrass (Agrostis stolonifera L.) in May 1998. Intact core samples (76 mm diam.) were removed from each plot and divided into two samples: a mat layer sample and the surface 0- to 76-mm depth of the root zone. Physical properties of both samples were determined. Three 25 mm diam. core samples of the mat layer were also collected from each plot and analyzed for thickness and the quantity of organic matter (OM). Bulk density and air-filled porosity (at -3 kPa) of the 0- to 76-mm depth indicated some compaction of the root zones from 1999 to 2005; capillary porosity was largely unchanged. Saturated hydraulic conductivity, however, indicated that compaction of the root zones did not restrict water flow as conductivity was relatively unchanged from 1999 to 2005. Conversely, substantial changes were observed in the mat layer. Mat layer thickness increased by an average of 17.8 mm from 1999 to 2005 and the quantity of OM increased by an average of 1.49 kg m-2. Total, air-filled and capillary porosity of the mat layer were 49 to 60% greater than that of the root zones in 2005; saturated hydraulic conductivity of the mat layer was 59% lower than the root zone. Thus, the development of the surface mat layer (zone of OM accumulation) was more responsible for changes in the physical properties of these plots.