On-farm Cyanobacterial Bio-fertilizer Production to Reduce the Carbon Footprint of Organic Fruit and Vegetable Production

On-farm Cyanobacterial Bio-fertilizer Production to Reduce the Carbon Footprint of Organic Fruit and Vegetable Production

Summary

Nitrogen (N) is the limiting factor for agricultural yields in most cropping systems. Nitrogen gas (N2) makes up approximately 78% of the Earth’s atmosphere, but in order to be useful for most microorganisms, plants, and animals, N must be in a “fixed” form such as ammonium or nitrate. Agriculture has become highly dependent on N fertilizers produced through a chemical N fixation process involving very high temperatures and pressures and, hence, requiring high fossil energy inputs. Some N-fixing bacteria are heterotrophic (e.g. Azotobacter and Azospirillum) and, thus, require a source of C for growth. In contrast, cyanobacteria are phototrophic N-fixers; they can fix nitrogen from the atmosphere and can power this process by fixing their own source of C via photosynthesis. Cyanobacterial bio-fertilizer (cyano-fertilizer) has the potential to become a new, sustainable source of N fertilizer; a fertilizer that can be produced on-farm, supplementing or replacing chemical fertilizers while decreasing fossil fuel consumption. Organic N fertilizer options are limited and are often low in nutrient content, expensive, bulky, and transported long distances. In arid and semi-arid areas, water limitations can preclude common fertility improvement methods such as leguminous cover crops/green manures. In contrast, intensive culture of cyanobacteria in covered raceways allows resource-efficient production of N fertilizer on small amounts of land. On-farm cyano-fertilizer production is an entirely new and innovative approach to providing crop N requirements using high-N bacterial biomass, while greatly reducing fertilizer manufacturing and transportation needs. However, for cyano-fertilizer production technology to be applied broadly to domestic agriculture, it must be scaled up and tested on farms, especially in the challenging environments of the semi-arid West. In this project, on-farm cyano-fertilizer production and use is being tested on one university research farm and four private organic farms (two vegetable farms, two fruit orchards).

Economic and environmental sustainability is being evaluated through yield impacts, cost/benefit analyses, and carbon footprint comparisons. Since cyano-fertilizer depends heavily on farmer knowledge and management, stakeholder input is guiding research and making cyano-fertilizer as easy to use as possible. Broad dissemination of educational materials (video, production manual, utilization factsheet, carbon footprint decision tool) are critical to widespread adoption. Field days, regional workshops, a webinar, and a website are being used for dissemination. Success of the project will result in working, profit-enhancing on-farm cyano-fertilizer systems and will lay the groundwork for further dissemination of the cyano-fertilizer approach. Cyano-fertilizer will eventually improve the profitability and sustainability of farms throughout the West and eventually the entire United States.

Objectives/Performance Targets

1) Optimize the yield and efficiency of an on-farm cyano-fertilizer production system

Task 1.1 – Determine if CO2 bubbling will enhance growth and N-fixation of cyanobacteria grown in outdoor raceways.

Task 1.2 – Evaluate batch vs. semi-continuous growth of cyanobacteria.

Task 1.3 – Explore methods to optimize light absorption.

2) Evaluate the utilization of cyano-fertilizer in irrigated fruit (peaches) and vegetable (lettuce, sweet corn) systems

Task 2.1—Compare cyano-fertilizer with commonly-used organic fertilizers (compost, fish emulsion, feather meal, and blood meal) in terms of impact on plant growth, yield, quality, and N recovery.

Task 2.2—Assess the effectiveness of cyano-fertilizer in contrast to farmers’ current practice on two working vegetable farms and two orchards.

Task 2.3–Evaluate the barriers to integration of cyano-fertilizer into current organic farming systems.

3) Quantify the direct costs and benefits of on-farm production and utilization of cyano-fertilizer to optimize economic returns for farmers

Task 3.1—Quantify the costs of cyano-fertilizer production as compared to commonly-used organic fertilizers.

Task 3.2—Appraise the economic benefits of cyano-fertilizer use.

Task 3.3 –Evaluate the economic feasibility of on-farm production and use of cyano-fertilizer.

4) Determine the carbon footprint of cyano-fertilizer compared to other methods of fertilization

Task 4.1—Monitor the N2O and CO2 emissions from cyano-fertilizer applied to land as compared to commonly-used organic fertilizers (compost, fish emulsion, feather meal, and blood meal).

Task 4.2—Modify the Daycent model to include cyano-fertilizer and other organic fertilizers for use in quantifying and comparing the carbon footprint of those fertilizers.

5) Impact farmer decision-making by sharing results through multiple methods

Task 5.1—Develop educational tools including a manual, factsheet, video, C footprint decision tool, and website.

Task 5.2—Disseminate educational tools and research results locally, regionally, nationally, and globally.

Task 5.3—Quantify and maximize producer adoption through continuous communication and feedback.

Accomplishments/Milestones

Objective 1—Optimize the cyano-fertilizer production system at the CSU Horticulture Farm and the two private vegetable farms (Happy Heart and Spring Kite). Initiate cyano-fertilizer production on the two private fruit farms (Ela Family Farm and Osito Orchard).

We initiated cyano-fertilizer production demonstrations on four private farms (Ela Family Farm, Osito Orchard, Spring Kite, and Happy Heart). In addition, our goal in our research raceways on the CSU Horticulture Research Farm is to increase productivity in an organically certifiable growth medium above the current two week batch production levels of 30 mg L-1 total Kjeldahl nitrogen. To improve production, we tested delta wing arrays to improve mixing and mass transfer of nutrients. We also supplemented production raceways with CO2 to maintain a pH of 9.5 or lower. Improved mixing produced no significant differences in biomass or nitrogen fixation in CO2 limited cultures. Supplementation of CO2 to limit pH at 9.5 produced small improvements in biomass but no difference in nitrogen concentration. Increasing the levels of CO2 supplemented and coupling the delta wings with CO2 supplementation still has strong potential to improve nutrient transfer and increase production of biomass and total nitrogen. If we can achieve this goal, the on-farm cyano-fertilizer production system will be competitive with other fertilizers, such as fish emulsion.

Objective 2—Evaluate cyano-fertilizer efficacy in replicated trials on CSU’s Horticulture Research Farm and at each of the four private farms. Determine the impact of cyano-fertilizer on crop yield and quality at all locations.

We initiated on-farm studies on cyano-fertilizer in mature peach trees (Osito Orchard), geriatric peach trees (Ela Family Farms), beets (Spring Kite Farm), and winter squash (Happy Heart Farm). In addition, we evaluated cyano-fertilizer on lettuce and sweet corn at CSU’s Horticulture Research Farm. In sweet corn, we measured the photosynthesis and transpiration rates and calculated the Water Use Efficiency (WUE) from these measurements. The treatments were solid organic fertilizers (feather meal and blood meal) and liquid organic fertilizers (fish emulsion and cyanobacteria) applied at 56 and 112 kg N ha-1. Liquid organic fertilizers were applied every two weeks after planting while the solid organic fertilizers were applied prior to planting. The feather meal treatment recorded the significantly lowest photosynthesis rate (19.5 µmol m-2 s-1) at 112 kg N ha-1 compared to other fertilizer treatments. The cyano-fertilizer treatment recorded the significantly lowest transpiration rate (0.6 mmol H2O m-2 s-1) at 56 kg N ha-1 compared with other fertilizer treatments. The 56 kg N ha-1 cyano-fertilizer treatment also recorded the significantly highest WUE (3 µmol CO2 mmol-1 H2O) compared to other fertilizer treatments. In conclusion, the cyano-fertilizer application resulted in significantly lower transpiration rate, thus recording a higher WUE at both N rates in drip irrigated sweet corn.

Objective 3—Determine land, water, labor, and power requirements for on-farm cyano-fertilizer production.

We determined the land, water, and power requirements for on-farm cyano-fertilizer production. Assuming a need for 10 lb N/acre as a sidedress, 0.02 acres (~780 sq ft) needs to be allocated for the raceway ponds for every acre of vegetable production (at current cyanobacterial growth and N fixation rates). As we make progress on objective 1, this land requirement will decline. We compared water use by the cyanobacteria per pound of N fixed to irrigation requirements of legumes. Cyanobacteria fix more N per unit of water than the clovers, about the same as hairy vetch, and less than winter peas. We are currently using electricity to drive the paddlewheels that keep the raceways agitated and aerated. Our measurements show that about 64 kWh are used to move the paddlewheel during each two week growth cycle. We are planning to develop a solar-powered setup to avoid the use of fossil energy and improve the overall sustainability of the system.

Objective 4—Survey organic farmers about their fertilizer choices and management practices. Measure greenhouse gas emissions from different organic fertilizers applied to vegetable crops at the CSU Horticulture Farm.

We evaluated the effect of four organic fertilizers: feather meal, blood meal, fish emulsion, and cyano-fertilizer applied at two rates, 56 and 112 kg N/ha, on greenhouse gas emissions from a lettuce field. Feather meal and blood meal increased the nitrous oxide (N2O) flux significantly as compared to the control, and the different rates of N in blood meal significantly impacted the N2O flux. The liquid fertilizers (fish emulsion and cyano-fertilizer) did not increase N2O flux compared to the control, probably due to their application in small doses throughout the growing season as compared to the pre-plant application of the feather meal and blood meal treatments. Most of the fertilizer treatments showed a significant impact on the CO2 flux as compared to the control; however, the low rate of cyano-fertilizer was not significantly different from the control. Therefore, our preliminary results show that cyano-fertilizer has lower greenhouse gas emissions than other organic fertilizers, particularly blood meal and feather meal.

Objective 5—Hold field days at the CSU Horticulture Farm and the four private farms, draft Cyanobacterial Bio-fertilizer Production Manual, build and update website, and connect to producers via Twitter and Facebook.

We held field days at the CSU Horticulture Farm (August 27, 2014) and two of the private farms (Osito Orchard on July 15, 2014; and Ela Family Farms on July 24, 2014) during summer 2014. These field days served to not only tell farmers about our project but also to learn more about their production practices and challenges. In addition, we updated our project website and have been building a follower base on Facebook.

Impacts and Contributions/Outcomes

To disseminate our research results to the scientific community, we made two scientific presentations at the annual American Society of Agronomy/Soil Science Society of America meeting (November 2014), one at the Organic Agriculture Research Symposium (February 2015), and four at the Western Nutrient Management Conference (March 2015).

In addition, we wrote two Extension articles disseminated through the CSU Extension system. We have initiated relationships with eOrganic and Appropriate Technology Transfer to Rural Areas to further disseminate our educational materials as they become available. Finally, we made five extension presentations (in addition to the field days described above) in CO, NM, OR, TX, and WI.

These presentations and articles are listed in detail below. They serve as first steps towards achieving the impacts planned for this project.

Proceedings
Sterle, D., G. Litus, F. Stonaker, S. Ela, and J.G. Davis. 2015. The effect of cyanobacteria biofertilizer on western Colorado organic peach quality and yield characteristics. Proc. of the Western Nutrient Management Conference; March 5-6 in Reno, NV.

Sukor, A., C. Ramsey, and J.G. Davis. 2015. Effects of commercial organic and cyanobacterial fertilizers on instantaneous water use efficiency in drip irrigated organic sweet corn. Proc. of the Western Nutrient Management Conference; March 5-6 in Reno, NV.

Wenz, J., H.N. Storteboom, and J.G. Davis. 2015. Effects of enhanced mixing and minimal CO2 supplementation on biomass and nitrogen concentration in a nitrogen-fixing Anabaena sp. Cyanobacteria biofertilizer production culture. Proc. of the Western Nutrient Management Conference; March 5-6 in Reno, NV.

Wickham, A., and J.G. Davis. 2015. Effect of liquid organic fertilizers and seaweed extract on Daucus carota var. Sativus growth characteristics. Proc. of the Western Nutrient Management Conference; March 5-6 in Reno, NV.

Abstracts
Sukor, A., and J.G. Davis. 2014. Influence of commercial organic and cyanobacterial fertilizers on yield and nitrogen use efficiency of lettuce and sweet corn. Paper 164-11. Soil Science Society of America Annual Meeting; Nov. 2-5, 2014 in Long Beach, CA.

Toonsiri, P. S.J. DelGrosso, J.G. Davis, A. Sukor, M. Smith, and M. Reyes-Fox. 2014. Comparison of organic fertilizer effects on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from a lettuce field.Paper 164-10. Soil Science Society of America Annual Meeting; Nov. 2-5, 2014 in Long Beach, CA.

Davis, J.G., H. Storteboom, and M.S. Massey. 2015. Developing an organic on-farm bio-fertilizer production system using cyanobacteria. Organic Agriculture Research Symposium; February 25-26, 2015 in Lacrosse, WI.

Extension Articles
Davis, J.G. 2014. CSU Team Begins Testing of On-farm Bio-Fertilizer Production on Local Orchards. Fruit Facts May 2014. Colorado State University Western Colorado Research Center. Grand Junction, CO.

Davis, J.G. 2014. CSU Soil Fertility Team Testing On-Farm Bio?Fertilizer Production for High?Value Crops. Southeast Farm and Ranch Newsletter October 2014. Colorado State University Cooperative Extension Southeast Area. Lamar, CO.

Extension Presentations
Sterle, D., and J.G. Davis. 2015. On-farm Cyano-fertilizer Production and Use in West Slope Peach Orchards. Western Colorado Horticulture Conference, Grand Junction, CO, January 15, 2015.

Davis, J.G. 2015. Organic Fertilizer Comparisons, Texas Organic Farmers and Gardeners Association, San Antonio, TX, January 30-31, 2015.

Davis, J.G. 2015. On-farm Production and Use of Algae as Fertilizer, New Mexico Organic Farming Conference, Albuquerque, NM, February 20-21, 2015.

Davis, J.G. 2015. Developing an Organic On-Farm Bio-fertilizer Production System using Cyanobacteria, Organicology, Portland, OR, February 6-7, 2015.

Davis, J.G. 2015. Developing an Organic On-Farm Bio-fertilizer Production System using Cyanobacteria, Midwest Organic and Sustainable Education Service (MOSES) Organic Farming Conference, Lacrosse, WI, February 26-28, 2015.

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