Estimating Total N In Everglades Soils Using Loss-On-Ignition Method.

Estimating total N in Everglades soils using loss-on-ignition method

 

Yu Wang^1*, Alan L. Wright², K.R. Reddy¹, T.Z. Osborne, and S. Newman³

The C and N contents of Everglades wetland soils can have major impacts on biogeochemical nutrient cycling and greenhouse gas emissions.  To gauge effectiveness of wetland restoration, it is imperative to quantify gains or losses in soil C and N stocks.  Due to high expense in processing large volumes of samples for automated CNS analysis, there is interest in investigating more cost-effective and simpler methods to measure soil C and N.  A total of 4595 soil samples from throughout Everglades wetlands were sampled to investigate efficacy of using loss-on-ignition (LOI) to estimate soil total N (TN).  The LOI method predicted total C (TC) well compared to automated CNS analysis for LOI >40%, which represented the vast majority of the Everglades.  Total organic C averaged 51% of LOI.  A significant relationship existed between LOI and TN for soils (r²=0.90), although the relationship was slightly improved for LOI in the range of 0-70% (r²=0.92). Soils with lower LOI (<70%) showed variable soil TC:TN ratios (6-70) because of the contribution of inorganic C. The TC:TN averaged 14.6 for LOI >70%,  Overall, direct linear regression between LOI and TN proved to be a good indicator of TN when LOI was <70%. However, for soils having LOI >70%, soil C is converted to total organic C, then using the TC:TN ratio of 14.6, total N can be calculated.