Developing An On-Farm Bio-Fertilizer Production System Using Cyanobacteria.

Agriculture is highly dependent on fertilizer made through energy-intensive industrial N fixation. Natural gas is used as both an ingredient and an energy source in the N fertilizer production process.  Organic agriculture is commonly dependent on off-farm N sources such as manure and compost, which contain about 1% N and are expensive to transport (if they are not produced on-farm), and products shipped very long distances, such as fish emulsion or blood meal.  On-farm fertilizer production has the potential to supply N to crops while reducing input costs and increasing energy-efficiency, ultimately improving agricultural sustainability. We are developing an on-farm biological N fixation system using cyanobacteria produced in ponds and harvested for use as fertilizer.  Cyanobacteria fix N from the air using energy from the Sun through photosynthesis; thus they have the potential to dramatically reduce fossil energy requirements for fertilizer production and transport.  We have begun a collection of cyanobacterial cultures from the USA and other countries and have done laboratory research to select the most productive cultures, optimize the nutrient solution, and evaluate water sources.  We are currently optimizing parameters such as depth and alkalinity in 100+ L raceways and have just begun testing cyanobacterial bio-fertilizer production in 2000+ L raceways, such as might be utilized on-farm.  In addition, we have begun to evaluate the use of cyanobacterial bio-fertilizer in both dried, solid forms (6-7% N) applied to soil and in liquid form applied through irrigation systems or through foliar applications.  For cyanobacterial bio-fertilizer to become part of the future of sustainable agriculture, it will be critical to maximize cyanobacterial growth and N fixation while minimizing costs and to optimize the use of the bio-fertilizer so that N use efficiency is high and losses of N to the environment are low.