Abstract
Providing food to the growing human population in a sustainable way is one of the greatest challenges of modern society. In this context, cyanobacterial biomass (CB) can function as a source of macronutrients to increase soil productivity. These organisms can be collected from the environment in considerable amounts, since they tend to grow in large blooms. However, some of these cyanobacterial strains produce toxins that need to be carefully monitored to avoid food accumulation. The objective of this work was to evaluate the possible use of toxic and non-toxic strains of CB as fertilizer supplement in the growth of economically relevant vegetables. One-month-old Raphanus sativus (radish) and Spinacia oleracea (spinach) plants were grown in pots in indoor controlled conditions. Six experimental conditions were set: (1) a control with no nutrient addition, (2) a recommended dose of a NK commercial fertilizer (CF), 0.6g of lyophilized CB of (3) a non-toxic strain of Cylindrospermopsis raciborskii, (4) a toxin-producing strain of C. raciborskii, (5) Microcystis aeruginosa, and (6) Anabaena sp. Several variables were estimated: in CB, this included the NPK dose addition, and in plants, the height, dry weight (dw) of the shoot and root, and the mineral content of plant edible parts. The mineral content in CB was estimated and compared with the recommended dose of CF, according to the information given by the fabricant label. We found no significative differences in N composition; nevertheless, there was a significative higher content in P and significative lower content in K in the CB. In the plants, we found no significative statistical differences between the treatments for the dw of radish root and spinach height. In spinach, the dw of the shoot in the M. aeruginosa treatment was significantly lower than the control, CF, and both the toxic and non-toxic C. raciborskii biomass. Additionally, in radish, the plant height and dw of the shoot M. aeruginosa treatment were significantly lower than in the toxic strain of C. raciborskii treatment. When analyzing mineral content in edible parts, we found that spinach treated with control and CF showed a higher content of Ca, Mo, N, P, and K, while in radish, the same two treatments plus the C. raciborskii toxic had higher Co and Fe content. M. aeruginosa amendment seems to impair shoot growth in both plant species. On the contrary, the toxic C. raciborskii CB seems to have a beneficial effect on growth and in mineral uptake on radish plants.
Author Contributions
Conceptualization, A.M., J.A., M.F., A.C. (Alexandre Campos) and V.V.; methodology, A.M., J.A., M.F., A.C. (Anabela Costa), A.C. (Alexandre Campos), R.A. and E.P.; software, A.M., J.A. and R.A.; validation, A.M., J.A., R.A, E.P., M.F. and A.C. (Alexandre Campos); formal analysis, A.M. and J.A.; investigation, A.M., J.A., M.F. and A.C. (Alexandre Campos); resources, A.M., J.A., E.P., M.F., A.C. (Alexandre Campos) and V.V.; data curation, A.M., J.A. and R.A.; writing—original draft preparation, A.M., M.F. and A.C. (Alexandre Campos); writing—review and editing, J.A., M.F. and A.C. (Alexandre Campos); supervision, J.A., M.F. and A.C. (Alexandre Campos); project administration, A.C. (Alexandre Campos) and V.V.; funding acquisition, A.C. (Alexandre Campos) and V.V. All authors have read and agreed to the published version of the manuscript.
Funding
This work received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 823860.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Acknowledgments
Many thanks to Nuno Vilas Boas, Diogo Lameirinhas Martins and Joana Costa Ferreira for helping us execute the experiment.
Conflicts of Interest
The authors declare no conflict of interest.
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