Monday, November 5, 2007
99-11
Dissolved Organic Carbon and Nutrients in Native Soil Under Three Turfgrasses and Two Sand-Based Sports-Fields.
Stephen Caster, David Zuberer, Frank Hons, Tony Provin, and Terry Gentry. Texas A&M University - Soil & Crop Sciences, College Station, TX 77843-2474
The urban landscape is diverse, including urban lawns, sports fields, and golf courses. Significant acreages are devoted to these uses in both urban and suburban areas. The intent of the present study was to characterize soil solutions moving through turfgrass stands on native soils and sand-based root zones, with regard to the effect of seasonality on nutrient concentrations, as well as the potential for offsite movement of nutrients to surrounding drainages. Soil solution samples were collected over a one and a half-year period using shallow wells in established turfgrass plots on native soils and from access to drainage systems of two sports fields with sand-based root zones, located on the Texas A&M University campus. The plots were planted with Bermuda, Zoysia, and St. Augustine grasses, and the sports fields (soccer complex and softball field) were planted with TifSport and TifWay Bermuda grasses respectively. We monitored dissolved organic carbon (DOC; carbon analyzer), dissolved organic nitrogen (DON; by persulfate oxidation followed by ICP analysis), and dissolved organic phosphorus (DOP; with Dowex anion exchange resin and ICP analysis). Other nutrients were determined by ICP spectrophotometry or by colorimetric methods. Rain was collected to determine potential additions of nutrients to the soils. In general, DOC values in the turf plot soil were greater than those in the sand-based root zones. Similar seasonal trends in DOC and DON occurred in both soil and sand-based root zones, with peak levels of DOC (135.25mg/L) and DON (22.80mg/L) appearing during mid to late summer. The ratio of DOC to DON ranged from approximately 10-15:1. DOP levels (20-25% of total soluble P) were consistent among the turf plots, but were markedly lower in the sports fields. Nitrate was consistently low (<1mg/L) except when fertilizer was applied to the turfgrasses. Further research in needed to quantify the offsite movement potential of dissolved organic nutrients, etc.