Respiration of Louisiana Freshwater Floating Marsh Soils Amended with Ammonium, Phosphate, and Sulfate

Wetland soils of the freshwater coastal deltaic regions of Louisiana have developed under decreasing influence from the Mississippi River, which has resulted in lower available nutrient conditions and sediment input relative to other coastal marshes. A laboratory soil respiration experiment was conducted to measure cumulative carbon dioxide (CO2) and methane (CH4) production in soils from a floating freshwater marsh in response to additions of added ammonium (N), phosphate (P), ammonium (N) + phosphate (P), and sulfate (S). CO2 respiration was significantly greater over a 28-day period than controls following ammonium N, phosphorus, and sulfate addition at 10 mg L−1. Nitrogen and phosphorus addition at 10 mg L−1 also increased methane production. The lower sulfate amendment (10 mg L−1) did not significantly increase CH4 production. In contrast, the greatest sulfate treatment (100 m l−1) significantly reduced total carbon (C) production by inhibiting CH4 production. The fact that soil C/N (20.2) and C/P (3...