Are Biofertilizers Actually Effective?
With global attention falling squarely on the impending disaster of climate change, manufacturers, politicians, consumers, and farmers are all looking at ways to contribute to the circular economy.
For supermarkets, agrichemical suppliers, and farmers the clear route to sustainability lies in using biofertilizers. Gone are the old ways of extracting a finite resource such as rock phosphate and transporting it halfway round the world to produce fertilizer. Gone too is the energy guzzling Haber-Bosch process. Instead of using manufactured ammonia, urea, phosphates, and nitrogen as fertilizer raw materials, agricultural supplements of bacteria and fungi will not only reduce agricultural CO2 emissions, but will limit algal blooming, improve soil health, reduce use of finite mineral resources, and increase food production for the planets predicted 9 billion inhabitants by 2050.
Fungi such as Rhizoglomus irregulare, and bacteria such as Rhizobium, Azotobacter, and Azospirilium will save the world. Or will they?
New research conducted by a team from a team centred on the University of British Columbia is claiming that biofertilizers are ineffective, with the study’s co-author Miranda Hart stating in an interview with the university website that, “Bio-fertilizers have been sold for decades and it's an industry worth millions of dollars. An important take away from this study is that there seemed to be no effect on the crops. If the farmer invested thousands on the inoculate, it may have been a waste of money.”
As the online journal Science Daily reports, “[While] It's common practice for farmers to use bio-fertilizers as a method to improve crop production ... A researcher is using her latest study to question whether soil additives are worth their salt. Despite a decades-long practice, there could be environmental consequences of adding bio-fertilizers into soil.”
The study was based on a common commercial AM fungal inoculant which was applied in four fields in Alberta and Saskatchewan, and the results analysed over the course of two growing seasons. The results, the authors claim, were extremely patchy, showing large variations in the proliferation of the fungus. In some areas the inoculant failed to become established, others saw partial success, while in one site, the fungi became invasive and ‘took over the resident fungal community in less than a year.’
The result have now been published in the journal, Science of the Total Environment, where the study states that, “While establishment and persistence of arbuscular mycorrhizal (AM) fungal inoculants in agricultural fields are critical to their success, little is known about how farming practices can affect their establishment in field. We developed a probe assay specific to a commercial AM fungal inoculant (Rhizoglomus irregulare DAOM197198) and tested its establishment among different grain cropping practices in the field. Establishment of the fungus was not related to cropping, or inoculation practices.” Significantly noting that, “Our results show that it is not yet possible to predict inoculation success in the field and use of biofertilizers requires further research under field conditions to identify key factors involved in establishment and persistence.”
As Hart observes, “It's very hard to determine if the microbes established in the soil. What we showed is that they often didn't establish. And even when they did, there was no difference in crop performance.”
Certainly, the study does raise some serious questions, such as whether it is possible to improve inoculation success rates, or if application methods and cropping practices could be improved.
However, as the industry journal Permaculture News states, general scientific opinion is that biofertilizers have many advantages over more traditional, bulk chemical fertilizers. These include:
· Biofertilizers have longer shelf life.
· Farmers can use biofertilizers quite easily.
· Biofertilizers are completely free of contamination.
· They are inexpensive.
· They bring high commercial revenues.
Hart agrees that bacteria and fungi can be highly beneficial to plants, and logically can improve crop yields with less damage to soil health than industrial chemical fertilizers. Stating on her website that, “We know that microbes help plants deal with nutrient and environmental stress.” She has spent many years examining the progress being made in the biofertilizer industry, and acknowledges that, “We're seeing how microbes can be used to reduce disease, increase nutrient uptake and create a more interesting product.”
However, she is also wary of unforeseen consequences, and is requesting more time and money for research to prove biofertilizer worth.
As she stated in a recent interview, “We still don’t understand what factors allow a fungus to establish in foreign soil.It’s hard to imagine that there is a ‘silver bullet’ fungus that will be a good fit with all systems and cropping types.”
Before adding that, “While we want microbes to act invasively in certain situations (agricultural application, remediation, restoration), are these deliberate inoculations resulting in unintentional introductions into natural systems? What we're doing is releasing invasive species into the environment and we don't know the long-term effect of what's happening to the soil.”
While the study had a limited reach, examining only one fungal biocide in four fields over two growing seasons, biofertilizer manufacturers will have been disappointed with the results. They are outcomes which fly in the face of countless other studies, both in vitro and in situ, which have found various biofertilizers to be an effective way to boost crop yields with minimal impact to the environment.
That said, the long-term impact of adding ‘invasive microbes’ to the soil is not yet fully understood, and as such the study’s results have got the biofertilizer industry talking. Which is always a good thing.
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