| dc.description.abstract | Utilization of slow-release fertilizers is a sustainable agricultural strategy which steadily and
consistently supplies nutrients throughout a plant’s life, thereby reducing fertilizer application
rates. Such fertilizers also promote effective nutrient utilization by crops minimizing nutrient
leaching and runoff to non-targeted areas, thereby maintaining a healthy environment. This study
developed a slow-release fertilizer named Azolla-Vermiculite Composite fertilizer, which is an
innovation from a blend of Azolla cristata powder as the mineral nutrient source, and exfoliated
vermiculite as the carrier material. Azolla is an aquatic fern symbiotically associated with the
nitrogen fixing cyanobacteria (Anabaena azollae). The cyanobacteria absorb atmospheric nitrogen
and avail it to Azolla in form of ammonium ions. This makes Azolla a rich source of nitrogen, a
characteristic that was manipulated in this study for developing the Azolla-Vermiculite Composite
fertilizer.
In this study, four species of Azolla were identified in Uganda through molecular characterization.
These species had sequence identities of 100, 93.36, 99.22 and 99.39% to the reference database
sequences namely; Azolla mexicana, Azolla microphylla, Azolla filiculoides and Azolla cristata,
respectively. The four species were found distributed in four out of the ten agro-ecological zones
of Uganda situated in close vicinity to large water masses of L.Victoria, L. Albert, and L. Kyoga.
Principal Component Analysis results revealed that maximum rainfall and altitude significantly
accounted for the variations in the distribution of Azolla in Uganda with factor loadings of 0.921
and 0.922, respectively.
Following experiments of domestication and cultivation of the four Azolla species in the small
ponds under uniform conditions, Azolla cristata was observed to have a significantly higher
nutrient bio-accumulation of nitrogen, phosphorus and potassium as the primary mineral nutrients
for plant growth (p<0.0001) in comparison with the other three species. It was on the basis of this
superiority that it was selected out for massive cultivation in a larger pond in preparation for
development of the slow-release Azolla-Vermiculite Composite fertilizer. These experiments
were conducted at Bukobero village, Masuliita sub-county Wakiso district.
Vermiculite is laminar hydrated clay like mineral with capacity to expand on heating and
treatment with some chemicals like hydrogen peroxide. It is non-reactive, has an alkaline pH and
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a high water holding capacity. In this innovation, exfoliated vermiculite was used because
exfoliation enhances the above properties. Laboratory analysis of both raw and exfoliated
vermiculite indicated a significant difference in water holding capacity, bulk density, and electro conductivity with p-values of 0.0002, 0.0033, and 0.0002 respectively. Furthermore, analysis of
vermiculite microstructure under the Scanning Electron Microscope exhibited a pure and asbestos
free form of vermiculite that was used in the experiment. X-ray Fluorescence exhibited the
richness of vermiculite in various minerals including; silica which contributed (>40%) and
phosphorus (<1%) among other minerals. Therefore, it was on the basis of these unique properties
exhibited by vermiculite after exfoliation, that it was selected for use as a carrier of Azolla powder
in developing the slow-release composite fertilizer.
When the Azolla-Vermiculite Composite (AVC) fertilizer was tested for growth performance,
yield and nutritional composition of Zea maize (maize), the change in height and yield varied
significantly between the composite fertilizer treated and control plants, with p values of <0.003
and ≤0.001 respectively. Proximate nutrient analysis of starch, reducing sugars, total
carbohydrates and pro-vitamin A carotenoids all varied significantly between AVC fertilizer
treated and control plants with p-values of <0.002. This significant variation was attributed to the
availability of sufficient concentrations of mineral nutrients in the fertilizer that enhanced these
nutritional components. In addition, all the fertilizer treated plants benefited from the water
retention property of exfoliated vermiculite in AVC fertilizer. Since yield is a factor of various
components with water as one of the major requirements, the water retention of AVC supported
effective progression of various physiological processes including photosynthesis, cell turgor,
nutrient uptake, among others. The result was enhanced accumulation of photoasssimilates in the
sink tissues resulting into a boost in yield and nutritional composition. Therefore, AVC fertilizer
is a promising Climate Smart Agricultural fertilizer technology for enhancing soil productivity
translating into better food production and improved environmental health. As a sustainability
measure, there is a need to improve this product so as to achieve its maximum potential in
agricultural production. This will serve as a contribution in support of the FAO strategic
framework 2021-2030 in the context of Agenda 2030 for sustainable development and Uganda’s
vision 2040. | en_US |
