Tuesday, November 14, 2006

Soil Organic Matter Fractions in Long-term Field Experiments.

Gobena Huluka, Dept Agronomy and Soils, Dept Agronomy and Soils, Auburn University, Auburn, AL 36849

Soil organic matter (SOM) has many important functions.  It affects soil structure, water holding and cation exchange capacities, microbial population and activity and overall soil quality. Many chemical and physical methods have been used to measure quantity of SOM fractions. The objective of this study was to determine the active, intermediate and the passive SOM fractions by density separation procedure. Seventy-four soil samples from the Old Rotation (established in 1896) and the Cullars Rotation (established 1911) were sampled at 0-15 and 15-30 cm depths and active, intermediate and passive SOM were determined. The separates were analyzed for C and N by LECO CN2000.  In addition, soil particle size, total C and N, pH, CEC, K, Mg, K, Ca, P, NO3-N, NH4-N, and microelements were analyzed by ICP and/or appropriate instruments. This study quantified the amount of SOM fractions in these historical fields and will enhance our understanding of how SOM fractions change over many years of different crop rotation, fertilization and other farming practices.