Effect of Plant-Derived and other Carbon Substrates on Asymbiotic N2-Fixation

Asymbiotic N2-fixation (also called associative N2-fixation when plants are involved) is highly variable over different sites and conditions but can occur at magnitudes great enough to be agronomically important. We previously reported finding highly active associative N2-fixation sites in a statewide search of Florida. Since energy that drives associative No-fixation is plant derived and restricting, we questioned whether N2-fixing bacteria in those highly active soils could utilize a greater proportion of the substrate in fixing nitrogen than those in low activity soils. We further questioned whether those highly active soils could utilize plant structural carbohydrates to fix nitrogen, and also wanted to get estimates of efficiency of substrate use for fixing nitrogen relative to other metabolic uses.