Influence of Cyanobacterial Bio-Fertilizer On Crop Micronutrient (Zn, Fe, beta-carotene) Content.

A series of greenhouse studies was carried out in order to compare cyanobacterial bio-fertilizer with either organic fertilizers used in the USA (composted manure and fish emulsion) or fertilizers available in Ethiopia (urea and compost).  Cyanobacteria cultured from local soils were used in the USA (Anabaena cylindrica) and Ethiopia (A. oscillarioides).  Cyanobacterial bio-fertilizer was applied in two forms: solid and liquid.  The fertilizers were applied at the same N rate, although the N rate varied by crop (kale, maize, chili pepper, lettuce, tomato), a no-fertilizer control was included, and a Randomized Complete Block Design was used with a minimum of three replications.  The solid cyanobacteria treatment yielded the same (or higher than) the urea treatment, depending on the crop.  In addition, cyanobacterial bio-fertilizers reduced soil pH and increased available soil Zn and Fe concentrations.  The solid cyanobacteria treatment significantly increased plant Zn and Fe concentrations as compared to both control and urea treatments.  A mass balance showed that the Fe applied in the cyanobacteria treatment could explain the increased plant Fe levels; however, this was not true for Zn.  Therefore, the pH reduction caused by the cyanobacterial bio-fertilizer probably contributed to increased plant availability of Zn.  Beta-carotene concentrations were significantly increased in lettuce and tomato crops grown with either solid or liquid cyanobacterial bio-fertilizer.  Analysis of β-carotene in the cyanobacteria showed that increased plant concentrations could be due to uptake of β-carotene from the cyanobacteria.  We are currently investigating this possibility.  Cyanobacterial bio-fertilizer has the potential not only to increase crop yields but also to improve food security in Ethiopia due to increased crop Zn, Fe, and β-carotene concentrations in crops.  Therefore, development of village-level cyanobacterial production processes is critical to making cyanobacterial bio-fertilizer accessible to smallholder farmers in order to achieve these impacts.