12 April 2024

Cyanobacteria are amazing biofertilizers for soil


According to a U.S. study, cyanobacteria or “blue-green algae” can be used to produce a biofertilizer suitable for iron-poor soils, thus turning into a valuable natural resource for farmers

by Matteo Cavallito


Cyanobacteria, also known as blue-green algae, are typically considered a threat to the ecosystem because of their ability to generate harmful toxins. Despite this, researchers now say, some of their characteristics could prove particularly valuable. According to research from Florida International University published in the journal Environments, for example, these same bacteria could even be used as natural fertilizers especially in iron-poor soils. Thus turning into a valuable resource for farmers.

The study

The investigation took place at an experimental site at the same university over the course of two years. Here the authors implemented four different treatments to evaluate the performance of cyanobacterial biofertilizers under the geographic and subtropical conditions of South Florida. In detail, the researchers treated one part of the soil with the algae-based biofertilizer alone, another with a chemical fertilizer, and a third with a 50-50 mixture of both. Finally, they left intact a space of soil that took on the role of a control area.

“Our results indicate that total biofertilizer (TB) application and total synthetic (TS) application produced about 29 to 33% higher SPAD (soil plant analytical development) readings than the control”, scientists say.

A crucial role in iron intake

In particular: “The absence of interveinal chlorosis (yellowing of leaves) in the TB and half and half (50% biofertilizer + 50% synthetic fertilizer) treatments suggests that the cyanobacteria-based biofertilizer had a role in supplying one of the critical micronutrients, iron (Fe). Analysis of the biofertilizer indicated 2000 ppm Fe content, which directly supports our observation”.

Moreover, “average plant height (61 cm), yield (130 gm per pot), and crop biomass (67 gm) productions were significantly higher in TB than in the control”.

Cyanobacteria also produce economic benefits

The study, in short, “documents the potential of cyanobacteria biofertilizers as a viable option compared to synthetic fertilizers for sustainable crop production and soil health improvement.” The availability of a new iron-rich natural resource should translate to farmers in reduced costs associated with cultivation, an International University statement says. Expecially in Florida, where agricultural soils notoriously suffer from some shortage of the element.

According to the authors, the statement continues, replacing synthetic fertilizers with cyanobacteria “can save them up to 15 percent in production costs without any loss of crops allowing farmers to stay competitive.” The use of cyanobacteria as a biofertilizer “can improve water quality by reducing nutrient runoff into surface water systems”. As well as finally increasing “organic matter levels in porous calcareous soil bettering soil aggregation and stability.”

Biofertilizers as an alternative to traditional products

As part of the so-called bioproducts, biofertilizers, whose main function is to provide nutrients to plants, have long attracted the attention of researchers. The use of alternative substances, in fact, appears particularly useful in countering the problems associated with the excessive use of synthetic fertilizers. These are well-known to be made by an energy-intensive process and are characterized by a high impact in terms of emissions. To the point of being a serious obstacle to achieving climate neutrality.

Their long-term use also contributes to the gradual depletion of nutrient availability in the soil.

According to FAO estimates in 2021, the latest year for which final data are available, the Planet’s soils absorbed 109 million tons of synthetic nitrogen fertilizers, 46 million tons of similar phosphorus products, and 40 million tons of potassium-based substances. A phenomenon that parallels the growing use of pesticides, which grew by 75 percent on a global scale in the first two decades of the century.