Carbon and Nitrogen Mineralization of Whole and Lipid Extracted Algae Meal In Sandy Soil.

Carbon and Nitrogen Mineralization of Whole and Lipid Extracted Algae Meal in Sandy Soil Katie L. Rothlisberger, Jamie L. Foster, Frank M. Hons, and Terry J. Gentry Texas Agrilife Research, Texas A&M University Humans have utilized algae, both macro- and microalgae, for centuries as food and medicines. Algae produced in controlled cultivation processes (open ponds or bioreactors) or harvested from natural environments are utilized in food, pharmaceutical, cosmetic, and industrial applications. As an energy source, algae present multiple possibilities for fuel products, such as biodiesel, ethanol, methane, jet fuel, and biocrude. Algae biofuel production would become more sustainable with high revenue end products made from lipid extracted algae meal. One possible added value agricultural coproduct is natural fertilizer and soil conditioner. The primary objectives of this study were to: 1) determine the rate of carbon (C) and nitrogen (N) mineralization of both whole and lipid extracted algae meal in a Weesatche sandy clay loam soil, 2) compare the microbial communities responsible for algae meal decomposition to those of lignocellulosic decomposition, and 3) determine the potential effects of algae meal on soil salinity. A microcosm study was conducted over a 56-d period with soil applications including: lipid extracted algae meal (1, 3, and 5%), whole algae meal (3%), wheat straw (1, 3, and 5%), and no amendment representing the control. Both destructive sampling and cumulative CO2 measurements were made after 3, 7, 14, 21, 28, and 56 d of incubation at 30? C. Cumulative CO2 evolution was measured by titrating base traps (1 M KOH) with 0.5 M HCl. Destructive soil samples were analyzed for total C and N, NO3--N, NH4+- N, pH and electrical conductivity, as well as bacterial to fungal ratios by qPCR. Discussion focuses primarily on significantly different mineralization rates and bacterial:fungal ratios between treatments and on potential effects of algae meal on soil salinity.