Preliminary observations regarding the abundance and diversity of soilborne, nitrogen-fixing bacteria under different turf-grass management systems.
Contributors:McSpadden Gardener, Brian
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Series/Report no.:Environmental Science Graduate Program. Graduate student poster competition, 2007
Urban soils have high spatial variability with respect to their physical, chemical and biological properties. Road or building constructions often involve removing the top layers of soil, thereby exposing subsoils to the surface. Experimental plots were established to monitor the response of nitrogen fixing bacterial populations to different turf-grass management systems. Tall Fescue was planted directly into topsoil (T), subsoil (S), or compost amended treatments of each (TC and SC, respectively) . After the establishment of the turf-grass, nitrogen fertilizers were added at 0, 2 or 4 lbs N per 1000ft2. Prior to seeding, the abundance of nifH genes detected by quantitative PCR was significantly greater in both topsoil-containing treatments (T and TC) than in the two subsoils. (P<0.060). After growing turf-grass for three months, nifH copy number was significantly higher in TC and SC soils (P<0.001) indicating positive influence of compost amendment on nitrogen fixing bacteria in both top and sub soils. Preliminary analysis of nifH sequences obtained from the initial sampling using LIBSHUFF indicated that the population structure of nitrogen-fixing bacteria may differ in the topsoil and subsoil (P=0.146). Thus, quantitative PCR and preliminary diversity study of nifH indicated potentially unique nitrogen fixing bacterial group in the subsoil. Impact of additional nitrogen fertilizer input and changes in nitrogen fixing bacterial community over time will be further studied.
Preliminary observation, On-going project
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