Saturday, 15 July 2006

Soil NO3 and NH4 over 14 years on a Long Term Soil Productivity study on the Lower Coastal Plain of North Carolina.

Robert J. Eaton and Kim Ludovici. USDA-Forest Service, Southern Research Station, 3041 Cornwallis Road, Durham, NC 27709

The Long Term Soil Productivity (LTSP) experiment is an international effort to determine the effects of organic matter removal, soil compaction, and competition control on forest productivity. Soil NO3 and NH4 concentrations have been measured 4 times over 14 years on the Croatan National Forest LTSP site. Studies initiated in the second and fifth growing seasons used the in-situ soil core incubation method to determine N availability from a subset of the treatment plots. These studies found differences in N-mineralization due to soil type, compaction, and vegetation control. During year 10, in-situ measures were compared with laboratory incubations. In-situ measures indicated a significant decrease in total inorganic N with increased soil compaction, while laboratory incubations documented significant decreases in NH4 in response to increased organic matter removal. Monthly soil samples are currently being taken to determine N availability after 14 growing seasons. Data will be presented and compared to previous results from this site.

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