Nutrient Availability and Ryegrass Productivity in Soils Amended with Lipid Extracted Algae.

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 derived from lipid extracted algae meal (LEA), such as organic fertilizers and soil conditioners. The primary objectives of this study were to determine the nutrient availability of LEA in Parrita sandy clay loam soil as well as the potential effects of LEA on soil salinity and the growth of a salt-tolerant ryegrass (Lolium multiflorum Lam. ‘TXR2011-S’). A field study was conducted using several soil treatments, including a control (soil plus chemical grade, inorganic N and P), 1.5% LEA, 3.0% LEA, and 3.0% organic material [1.5% LEA plus 1.5% wheat straw (Triticum aestivum L.; WS)]. Soil from a nearby field was collected from a 0-15 cm depth, homogenized, sieved (< 4 mm) and used to fill the bottom 15 cm of PVC columns [33 cm x 10 cm (i.d.)]. Treatments were mixed with homogenized soil at the specified rate and then used to fill the top 15 cm of columns to a bulk density of ~ 0.8 g cm^-3. Holes were dug and columns were inserted into soil at ground level. Approximately 90 d after treatment initiation, the columns were seeded with ryegrass at 20 seed column^-1. Seedling emergence and plant growth were monitored initially and throughout the duration of the study (~ 85 d). Herbage mass was measured by harvesting forage within the column to ground level and was analyzed for total nutrients. After harvesting, soil was sampled from the 0-5, 5-15 and 15-30 cm depths and analyzed for total C and N, macro and micronutrients, pH and electrical conductivity. The discussion will focus on significant differences in nutrient availability, soil salinity, and herbage mass as affected by LEA soil amendments and other treatments.