Optimizing Growth and Nitrogen Fixation In Organic Cyanobacterial Biofertilizer Production.

Nitrogen is one of the most crucial nutrients for plants. In organic agriculture, nitrogen fertilizers are limited to few sources such as compost or manure. In many cases, these sources are not produced on-farm and must be transported, thus incurring both time and expense. Cyanobacteria are microorganisms that can carry out photosynthesis to generate energy and also fix N from the atmosphere. The on-farm production of nitrogen-fixing cyanobacteria offers farmers an alternative nitrogen source that can be produced directly on farm. Cyanobacteria can be grown in large circulating ponds called raceways and either harvested and dried or directly applied to crops (fertigation). The application of cyanobacterial biofertilizer on certified organic land requires a nutrient solution of organically certified components. The goal of this project is to develop an organically certified nutrient media that can support the growth and N-fixation of cyanobacteria in large-scale production. In this study, we built on previous lab studies by comparing the large-scale production of cyanobacteria grown in an organic nutrient media to the production of cyanobacteria grown in the original non-organic nutrient media (Allen and Arnon). Cyanobacteria were grown in 2000-L raceways in a replicated randomized block design with two treatments: organic nutrient media and non-organic nutrient media. Raceways were aerated and mixed with a paddle wheel. Water temperature, pH, OD, chlorophyll content, and photosynthetic efficiency (Fm/Fv) were measured routinely over the 14-day growth period. Initial and final samples were analyzed for TKN, total N, and nutrient content (using ICP).  The results from OD and chlorophyll content suggest that the organic nutrient solution supports growth equal to that of Allen and Arnon. Ultimately, we aim to provide farmers with a continual organic nitrogen source that can be produced on-farm and directly applied to crops.

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See more from this Division: SSSA Division: Soil Biology & Biochemistry
See more from this Session: Microbial Community Dynamics In Farming Systems: I

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