Physical and Chemical Soil Assessment Following Amendments of Lipid Extracted Algae Meal.

As an energy source, extracted algal oil presents 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 (LEA). One possible added value agricultural coproduct is natural fertilizer and soil conditioner. The primary objectives of this study were to determine the rate of carbon (C) and nitrogen (N) mineralization and nutrient availability of LEA in a Weesatche sandy clay loam soil and the potential effects of algae meal on soil salinity and plant growth. A long term microcosm study was conducted over a 224-d period with soil applications including: LEA meal (1.5 and 3%) and wheat straw (1.5%), and no amendment representing the control. Both destructive sampling and cumulative CO₂ measurements were made after 1, 4, 7, 14, 28, 56, 112, 168, and 224 d of incubation at 30 °C. An additional glass house study was conducted utilizing the same microcosm treatments, but with one additional treatment of 1.5% wheat straw plus 1.5% LEA. The Weesatche soil was amended with these treatments and added to the top 15 cm of a 30 cm column which contained unamended soil in the lower portion. After incubating for 14 d with the soil water content maintained at 60% water filled pore space, the columns were seeded with forages, including: foxtail millet (Setaria italica), sorghum-sudan grass hybrid (Sorghum bicolor x Sorghum bicolor spp. drummondii), and pearl millet (Pennisetum glaucum).  Discussion focuses primarily on significantly different mineralization rates between treatments and on potential effects of algae meal on soil salinity for the microcosm study, while that of the glass house study concentrates largely on nutrient availability, plant growth, and rooting depth as affected by LEA soil amendments.