Nitrate Removal from Solution with Vermicompost: Mechanisms, Kinetics and Point of Zero Charge Determination.

Nitrogen (N) pollution from agricultural sources is a global environmental quality issue. The use of organic fertilizers including vermicomposts has been proposed as a method to decrease N losses in agricultural production; however, the ability of vermicomposts to affect N dynamics, in particular NO₃^- immobilization, is not well understood. This study was conducted to determine the ability of vermicompost to remove NO₃^- from solution. The kinetics, maximum specific nitrate adsorption capacity (MSNAC), and point of zero charge (PZC) of a dairy-manure vermicompost with added NO₃^- was investigated in a series of aerobic batch tests. The vermicompost was pre-washed in deionized water to remove soluble N.  The dominant mechanism of nitrate removal from solution (e.g. biotic or abiotic) was determined by comparing an autoclaved vermicompost to a non-autoclaved vermicompost. Autoclaved vermicompost was effective in removing 88% of an added 1.5mM NO₃^-solution while non-autoclaved vermicompost removed 70% after 290h. Kinetic study results are inconclusive regarding a dominant mechanism of NO₃^- removal from solution; however, the NO₃^-. removal capacity of both vermicomposts appear to be high.  Experiments are underway to measure MSNAC and PZC of vermicompost and results will be reported at the 2016 SSSA annual meeting.