Soil Phosphorus Cycling in a Non-Agriculture Grassland Ecosystem: Influence of Fertilization.

The Konza tallgrass prairie ecosystem is inherently low in plant nutrients.   Sources of P available for plant uptake include slow weathering of P containing parent material, mineralization of organic P, and the solubilization of inorganic P by microorganisms.  The main objectives of this study are to observe how the addition of P with or without N influences the inorganic and organic P pools in the grassland soil system. In 2002, a P and N fertilization experiment was developed and implemented on a well -drained, shallow, cherty silt loam/ cherty silt clay loam soil with a soil pH of 6 on the Konza Prairie Biological Station, Manhattan, KS.  The randomized 4x2 factorial design included four levels of triple super phosphate fertilizer (0, 2.5, 5.0, 10.0 g P/m²) and two ammonium nitrate additions (0, 10 g N/ m²) with six replications for a total of 48 plots in factorial arrangement.

Soil samples will be collected in May 2014 to a 15 cm depth and divided into three 5 cm sections, three cores per plot.   The soil samples will be analyzed for total P and soil P fractions using a modified Hedley soil fractionation scheme.   These measurements will be supported by speciation of P in soil using direct techniques such as ³¹P-nuclear magnetic resonance (NMR) spectroscopy and X-ray Absorption Near Edge Structure (XANES) spectroscopy.   Conclusions are pending.