Long-term Organic Farming Impacts on Soil Fertility

Cyanobacteria are versatile organisms, able to generate oxygen, pull nitrogen from the air, and survive in virtually every ecosystem on the planet - all on a diet of sunlight, carbon dioxide and water. Researchers at Colorado State University are now putting these solar-powered microbes, commonly known as blue-green algae, to work producing high-quality organic fertilizer.
A research team led by Jessica Davis, Ph.D., has shown that cyanobacteria can be grown and transformed into high-quality liquid bio-fertilizer on working farms, and that greenhouse vegetables grown with this fertilizer contain high levels of beta-carotene, a key nutrient.
Now, with financial support from Organic Farming Research Foundation, Davis’s team is broadening its analysis of organic fertilizers, aiming to provide farmers with solid data in an area that still relies heavily on industry advertising and anecdotal evidence.
“We got into this research looking for nitrogen from organic sources other than manure and legumes,” Davis said. “But like most research, one answer leads to another ten questions, and we stumbled upon these phytohormones and their effects on crop health and nutritional quality. “
Phytohormones are a class of plant-produced chemicals that influence plant growth and development, including rooting, branching, and overall vigor. Phytohormones are not considered nutrients, but rather growth regulators, and appear in trace quantities compared to the standard fertilizer troika of NPK (nitrogen, phosphorus and potassium).
“The scientific community has pooh-poohed these claims in the past, basically saying that (the presence of phytochemicals in fertilizer) is irrelevant or not proven at best,” Davis said. “But we have seen things in our greenhouse studies indicating that the source of the nitrogen affects flowering and branching and other unexpected things. It points to drivers besides just the macro-nutrients.”
Davis’ team will utilize laboratory analysis to quantify the concentration of various phytohormones in organic fertilizers including fish emulsion, kelp, compost and farm-grown cyanobacteria solutions. Researchers will also test the fertilizers on field crops of carrots and peppers, and assess fertilizer impact on growth, yield and nutrient levels in produce.
Bio-fertilizer generated by cyanobacteria will be tested on existing organic peach orchards, in collaboration with two Colorado farmers, to provide comparison with standard organic practices.
The Colorado researchers will also produce a cost/benefit analysis of on-farm production of cyanobacteria fertilizer and publish the data, allowing organic farmers more opportunity to optimize economic returns.
Like conventional farmers, organic growers rely on nitrogen fertilizers to feed their crops. But even certified organic fertilizers face limits to sustainability. Manure and compost are commonly used in organic cropping, but are low in nitrogen, high in bulk, are often trucked in from great distances, and can contribute to soil salinization.
Nitrogen-fixing cover crops pull nitrogen from the atmosphere into the soil, but also require water, limiting usefulness in semi-arid areas. And amendments such as fish emulsion and guano are costly, only marginally renewable and can impose a big carbon footprint.
Cyanobacterial bio-fertilizer could potentially prove more sustainable and cost-effective than other traditional organic fertilizers, Davis said, with its ability to convert sunlight into usable nitrogen, and the potential for farmers to produce their own supplies on site.  The nitrogen provided by cyanobacterial bio-fertilizer is also available to plants much more quickly that the nitrogen provided by slow-release organics such as compost and manure.
 “Our intent is to empower farmers to close the circle of soil fertility, reduce their carbon footprint, reduce costs, and increase self-sufficiency,” Davis said. “It adds a new layer to the concept of ‘local food’. “
For more information on Dr. Davis’ work, visit her website at www.thinairnitrogen.com, watch her TEDx presentation at www.youtube.com/watch?v=DxXT73wzIYA, or contact her at Jessica.Davis@ColoState.edu