Outcome of Long-term Organic Farming Impacts on Soil Fertility

Supplying adequate nitrogen (N) to organic crops at the right time is a challenge. Our research
team is developing a system for growing cyanobacterial bio-fertilizer (cyano-fertilizer) on farms and
applying it through irrigation systems. Cyanobacteria are ubiquitous in soils and can fix N from the
air using energy from the Sun through photosynthesis. Preliminary data from greenhouse studies
has shown that cyano-fertilizer increased flowering and crop beta-carotene concentrations. The
purpose of this project is to broaden this work to include fish emulsion (hydrolyzed and nonhydrolyzed) and kelp and evaluate their phytohormone concentrations and impact on nutritive
value of organic crops. 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. In this project, on-farm cyano-fertilizer
production and use were tested on a university research farm and two private orchards. The
objectives of this project are listed below with a brief summary of our findings:
a) to quantify phytohormone concentrations (auxin and cytokinin, in particular) in organic
fertilizers (including compost, fish emulsion, hydrolyzed fish emulsion, kelp, and
cyanobacterial bio-fertilizer) Six of the seven organic fertilizers analyzed were found to contain auxin and salicylic acid; however, none of the fertilizers contained any measurable levels of cytokinins. The non-hydrolyzed fish emulsion contained a high auxin content and a low salicylic acid content, while the hydrolyzed fish emulsion was relatively high in salicylic acid and low in auxin. The cyano-fertilizer was high in both phytohormones.
b) to assess the impact of phytohormones present in organic fertilizers on plant growth, yield,
and quality of carrots and peppers (including β-carotene concentrations) In both the field-grown carrot study and the greenhouse pepper experiment, the cyano-fertilizer and the non-hydrolyzed fish emulsion treatments had the highest crop yields. This may be due to both of these fertilizers resulting in the largest auxin application rates.
There was no fertilizer effect on beta-carotene concentration in peppers; however, the nonhydrolyzed
fish emulsion had higher beta-carotene concentration compared to other organic fertilizer treatments when applied to lettuce. In the lettuce study, the auxin application rates were positively correlated with the beta-carotene concentrations. In the pepper study, fertilizer treatment affected phytohormone levels in pepper leaves at harvest time. Specifically, the non-hydrolyzed fish treatment had higher abscisic acid and 12-oxophytodienoic acid concentrations in the leaves.
In addition, both foliar seaweed products resulted in a significant reduction in the number of bellshaped peppers harvested.
c) to monitor the impact of cyanobacterial bio-fertilizer on peaches as compared to farmer’s
standard practice through on-farm, participatory research In the on-farm research carried out on organic peach orchards, application of cyano-fertilizer in addition to compost increased peach yield and reduced the growth of the tree trunks. In addition, cyano-fertilizer increased the SPAD chlorophyll readings of the leaves, and the SPAD readings were positively correlated to the distal leaf iron concentration.
d) to quantify the direct costs and benefits of on-farm production and utilization of biofertilizer
to optimize economic returns for organic farmers The economic evaluation of the on-farm cyano-fertilizer production system found that cyanofertilizer is already competitive with the most expensive organic N fertilizers. However, to be competitive with fish emulsions and blood and feather meals, the cost per lb of N must be reduced to about half of current costs. Based on smaller-scale experiments with supplemental CO2, it is likely that we will be able to double N fixation while increasing costs by only about 20%. We will be evaluating this approach in field-scale raceways during the summer of 2016.
e) to impact farmer decision-making regarding fertilizer selection by sharing results through
multiple methods Eighteen presentations were made to farmer audiences and other conferences to disseminate the results of these studies.


Outcome PDF: