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Evaluation of cyanobacterial biofertilizer as a supplemental or solitary fertilizer on peach yields, leaf tissue nutrient concentration, and trunk growth




Sterle, David, author
Davis, Jessica G., advisor
Caspari, Horst, committee member
Fonte, Steven, committee member

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Nitrogen (N) is the nutrient applied in the greatest quantities to peach trees and is a necessary component of proteins. As a result, carbon assimilation is dependent upon adequate levels of N in leaf tissue. Cyanobacteria are a type of bacteria which can fix gaseous N from the atmosphere enzymatically. This N fixation can be exploited in a cyanobacterial biofertilizer (cyano-fertilizer) production raceway, which allows farmers to grow their own source of N with relatively small energy inputs. Cyano-fertilizer was grown on three peach farms in Western Colorado, and applied to peach orchards in combination with a chicken feather meal (mixed with meat and bone meal), a dried chicken manure, and separately in comparison to a conventional foliar fertilizer, fish emulsion fertilizer foliarly applied, and a soil application of fish emulsion fertilizer. Treatments were assigned to experimental units across three separate farms (Farms A, B, and C) and arranged using Randomized Complete Block Designs. Peach fruit yield, trunk cross sectional area, leaf tissue nutrient concentrations, soil nutrient concentrations, SPAD and fruit juice quality characteristics were measured. A significant fruit yield increase was seen on Farm B in treatments which included cyano-fertilizer and manure (Cyano-Manure), versus manure alone (No-Cyano). Trunk cross sectional area showed less growth in treatments including cyanobacteria on Farm B. Significantly higher leaf tissue S, P, and Cu concentrations were found in Cyano-Manure treatments on Farm B; however, significantly greater Ca concentrations were found in the No-Cyano treatment. Chlorosis was present throughout Farm B and so relative leaf chlorophyll content was estimated by measuring Soil Plant Analysis Development (SPAD). SPAD readings were positively correlated with leaf Fe concentration. In the 2015 fertilization section, SPAD readings were higher in Cyano-Manure treatments despite the relatively low amount of Fe present in the cyano-fertilizer, suggesting that cyano-fertilizer may have increased Fe uptake by the trees. Significant differences in leaf micronutrient concentrations were found among treatments in Farm C. Across all farms, treatment effects were masked by three unforeseen events. First, a large infestation of aphids on Farm A caused the death of young vegetative tissue and also killed young peach fruit. Second, a freezing event during bloom, killed most of the fruit on two of the farms. Lastly, there were prior fertilizations earlier in the season on Farm C which lowered the impact additional fertilizer had on the trees.


2016 Spring.
Includes bibliographical references.

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