352-6 Incorporating Carbon Saturation Concepts and Nitrogen Retention Theory.



Wednesday, October 19, 2011: 10:00 AM
Henry Gonzalez Convention Center, Room 006A, River Level

Michael Castellano, Department of Agronomy, Iowa State University, Ames, IA, Jason Kaye, Deptartment of Crop and Soil Sciences, Pennsylvania State University, University Park, PA, Henry Lin, The Pennsylvania State University, University Park, PA and John Schmidt, USDA-ARS-PSWMRU, University Park, PA
Recent advances in soil C saturation concepts have increased our understanding of soil C storage and mineralization without explicit links to N retention and saturation theories.  Here, we exploit a soil texture gradient to test hypotheses that link soil organic C saturation with soil 15N retention and nitrification. At our site, mineral-associated organic matter (MAOM) concentrations in the silt + clay particle fraction (g MAOM g silt + clay-1) were negatively correlated with the fraction of NH4-N transferred to MAOM during a 3d in situ incubation (R = -0.82), but positively correlated with potential net nitrification (R = 0.76).  Moreover, NH4-N transfer to MAOM was negatively correlated with potential net nitrification (R = -0.74).  MAOM is considered to be resistant to mineralization.  Carbon saturation theory demonstrates that the proportion of new C inputs that can be stabilized in MAOM decreases in proportion to the amount of C already present in the fraction; C inputs not stabilized in MAOM are susceptible to rapid mineralization.  By demonstrating that NH4-N stabilization in MAOM is similar to C stabilization in MAOM and associated with nitrification, we extend soil C saturation theory to mineral N and link it with N retention and saturation theories.  Incorporating the organic matter retention capacity of fine mineral particles into N saturation theory will improve predictions of N saturation rates and resolve inconsistent relationships between soil organic matter, texture, N mineralization, and N retention.
See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: Soil Carbon and Nitrogen: Microbial Transformations and Fluxes