Study Shows Biofertilizer Enhances Plant Growth and Resilience, But Not Adequately Regulated

29
Jan

Study Shows Biofertilizer Enhances Plant Growth and Resilience, But Not Adequately Regulated

(Beyond Pesticides, January 29, 2025) A team of researchers recently discovered the benefits of using natural biofertilizers and biostimulants in the production of tomatoes, the results of a two-year study featured in the Journal of the Science of Food and Agriculture. When the researchers added a biofertilizer consisting of fungi and bacteria, and/or a biostimulant made of algae, the tomato plants grew bigger, faster, and produced significantly more (and sweeter) fruit than plants that received neither treatment. This research, published in August 2024, adds to a growing body of evidence that non-synthetic, natural fertilizer alternatives can support a global transition away from the toxic chemical treadmill of modern commercial farming.

[A note about the definition of plant biostimulants. They are substances or microorganisms that enhance natural plant processes, improving resource efficiency, stress tolerance, and overall growth without directly providing nutrients or controlling pests. There is ongoing confusion regarding a lack of a set definition, as some biostimulants overlap in function with fertilizers or biocontrol agents. The definition of biofertilizers—also referred to as inoculants, bioinoculants, or bioformulations—are products containing beneficial microorganisms in active or inactive forms. These microorganisms, applied singly or in combination, colonize the rhizosphere or plant tissues to enhance nutrient availability (e.g., nitrogen, phosphorus, potassium) and uptake, ultimately improving plant growth and crop productivity. See here and here].

Also known as “plant growth-promoting microorganisms” (PGPM), microbial biofertilizers consist of naturally occurring soil microorganisms, such as rhizobacteria and fungi. By forming symbiotic relationships with a plant’s root system, previous studies have shown that they can enhance plant growth and increase a plant’s tolerance for stressors such as drought and disease, which could serve as an entry towards transitioning to organic agricultural practices worldwide.

As Emanuele Radicetti, PhD, an associate professor at the University of Ferrara, Italy, explains, “There is an urgent need to develop sustainable agroecosystems that can ensure sufficient crop yield over a long-term period. Biofertilisers are gradually emerging as a promising, nature-based alternative that reduces agroecosystem inputs by enhancing organism interactions.”

Methods and materials

The study, “Impact of sustainable agronomic practices for the improvement of agricultural production,” investigates the effects of plant growth-promoting microorganisms (PGPMs) and algae-based biostimulants on the growth and yield of tomatoes (Solanum lycopersicum L.) in organic farming systems. The experiment was conducted on an organic farm in Ferrara, Italy, over the 2022 and 2023 growing seasons. The researchers hypothesized that the combined application of plant growth-promoting microorganisms (PGPMs) and algae-based biostimulants could improve organic tomato production in organic production (which uses no synthetic fertilizer or pesticides). This study adds to the growing evidence that organic food production practices can be optimized for higher yield, growth, and quality without petrochemical pesticides and fertilizers. The study objectives were threefold:

Evaluate the effects of PGPMs on plantlet establishment under field conditions;
Assess the impact of combined PGPM and algae-based biostimulant application on tomato growth; and,
Investigate how the integrated use of PGPMs and algae-based biostimulants affects tomato yield and fruit quality.

The two treatments of microbial biofertilizers and one biostimulant are

Microbial biofertilizer PGPM_1 (MICOSAT F®) contains mycorrhizal fungi (Glomus spp.), Trichoderma spp., Agrobacterium radiobacter, Bacillus amyloliquefaciens, Pochonia chlamydosporia, Trichoderma harzianum, Streptomyces spp., and Pichia pastor, produced by CCS Centro Colture Sperimentali, Aosta, Italy.
Microbial biofertilizer PGPM_2 (MYCOUP) contains Glomus iranicum var. tenuihypharum (1%) and rhizosphere bacteria, produced by BIOGARD Division, Bergamo, Italy.
Algae-based biosimulant was derived from spent low-salinity BG11 medium used to cultivate the green microalga Neochloris oleoabundans UTEX 1195, produced by the University of Ferrara botanical lab, applied at a concentration of 0.5% and 1.0%.

Treatment applications

Microbial Biofertilizers: Applied at transplanting, with PGPM-1 at 10 kg/ha and PGPM-2 at 3 kg/ha, delivered via drip irrigation five days after transplanting. In addition, no inoculated tomato plants were cultivated as control group (No_PGPM).

Algae-Based Biostimulants: Foliar applications were made at 15 and 30 days post-transplant, using 0.5% and 1% concentrations. Control plants did not receive any biostimulants (No_Biost).

Control group details

The control groups for both microbial biofertilizers (No_PGPM) and biostimulants (No_Biost) are essential for establishing baseline comparisons, and the experiment design allows testing of two concentrations of biostimulants alone, PGPM formulations alone, and in combination with biostimulants against a control with no biofertilizer (PGPM) or biostimulant used.

Organic farm site description

The experiment was conducted at the organic F.lli Baretta farm in Ferrara, Italy. The site features a mild thermos-Mediterranean climate with an average annual rainfall of 617 mm. The soil conditions are suitable for organic agriculture (most recently for organic wheat production). Soil properties include:

34.4% sand, 49.0% silt, and 16.6% clay, pH of 7.8. 1.13% organic matter. 1.29% total nitrogen.

Results and improved impacts on yield and quality

PGPMs contribute to improved fruit size and sugar content. Biostimulants enhance fruit color and lycopene levels. The combination of treatments significantly increases marketable fruit yield, minimizes unmarketable produce, and elevates overall fruit quality. The control treatment (No_PGPM + No_Biost) provides a baseline for tomato production without any amendments. These control plots exhibit the lowest growth and yield metrics.

Natural biostimulants developed from algae are also being developed for use in organic agriculture. Easily applied as a foliar spray, biostimulants provide the natural compounds necessary for plant growth and, in comparison with conventional agricultural products, are not only environmentally friendly but more cost-effective. “Algae extracts are considered a rich source of plant biostimulants and provide a renewable option for improving crop quality and yield,” explained Dr. Radicetti. “Even at low doses they have the capacity to support plant development, especially under stressed conditions, which are becoming more frequent with climate change.”

The results of the study, stunning the researchers, demonstrate a significant increase in plant health and fruit yields; 30 days after transplanting the samples, seedlings treated with biofertilizer exhibited higher fresh and dried biomass, more and bigger leaves, longer and denser roots, and increased height compared to the control group. Plants treated with the highest concentration of the algae biostimulant and/or one of the two tested biofertilizers produced the greatest yield of fruit and the greatest number of marketable tomatoes averaging 63-67 tons per hectare. Conversely, the least amount of marketable fruit came from the control plants that received neither biostimulant nor biofertilizer: 26 tons of fruit per hectare. Plants dosed with the 0.5% concentration offered an intermediate yield of 42-46 tons per hectare.

Organic fertilizers have been used throughout the history of agriculture and, adding to the body of science, this research indicates that highly effective organic alternatives to petrochemical synthetic fertilizers conceivably could be relied used effectively on a massive scale. In the words of Dr. Radicetti, “There is an urgent need to develop sustainable agroecosystems that can ensure sufficient crop yield over a long-term period… Biofertilizers are gradually emerging as a promising, nature-based alternative that reduces agroecosystem inputs by enhancing organism interactions.” These “fertilizers” feed the biological life in the soil, and do not directly feed the plants.

Commercial industry falls short

The global soil health industry, valued in the billions, has seen rapid expansion as farmers and gardeners seek eco-friendly solutions to enhance crop yields and soil sustainability, such as the PGPM biofertilizers featured above. However, recent reporting by Harvest Public Media illustrates that certain commercial PGPM products fall short of their promises. As noted by Celia Llopis-Jepsen, a reporter with the Kansas News Service and the creator and host of the environmental podcast “Up From Dust,” most biofertilizers and related products are not subject to mandatory independent testing or even thorough self-regulation in the U.S. As a result, their potential benefits, well-documented in scientific research, often fail to translate into reliable commercial applications. Adopting a structure similar to the Organic Food Production Act and the National Organic Standards Board (NOSB) could provide a solution, as this framework has been effective in supporting the integrity of the U.S.-certified organic food sector by incorporating independent third-party inspections, transparent decision-making process open to public comment, and a system for continuous improvement, including review of approved inputs and products.

Such a system for plant growth-promoting products would help ensure that their scientific potential is fully realized in practice. Without these measures, the benefits promised by biofertilizers and other PGPMs may remain underutilized, leaving farmers and consumers with fewer dependable, environmentally sustainable options. See a recent article for a meta-analysis of globally sourced commercial mycorrhizal inoculants.

The appeal of soil microbes amid concerns over synthetic fertilizers

The growing interest in soil microbiomes is driven in part by dissatisfaction with synthetic fertilizers, which, while boosting yields, have caused environmental harm, including groundwater contamination and the expansion of the Gulf of Mexico’s “d ead zone.” As Beyond Pesticides has reported, synthetic fertilizers cause demonstrated environmental harm, negative climate impacts, decreased soil carbon sequestration, and devastating harm to farmers. As Harvest Public Media reports, many growers are turning to microbial products, drawn by their potential to enhance soil health and reduce dependency on chemical inputs.

Some commercial synthetic fertilizer products, including from The Scotts Miracle-Gro Company, allegedly mislead consumers on the hazardous nature of their fertilizer products, which are marketed as “eco-friendly” and “sustainable,” while containing sewage sludge (biosolids) contaminated with per- and polyfluoroalkyl substances (PFAS). In October 2024, Beyond Pesticides filed suit in two cases, Beyond Pesticides v. Miracle-Gro Co. and Beyond Pesticides v. GreenTechnologies, LLC, in D.C. Superior Court. The complaint cites test results showing PFAS residues in the companies’ fertilizers and numerous scientific studies on the adverse effects of PFAS to public health, wildlife, and pollinators. “Companies that market hazardous substances while claiming environmental and health benefits are misleading consumers who seek out products to protect themselves, their families, and the ecosystems in which they live,” said Jay Feldman, executive director of Beyond Pesticides. “Our litigation seeks to put a stop to this deceptive practice in the marketplace, where there are products and practices that are truly healthful and protective of nature,” Mr. Feldman continued. Update as reported in the New York Times: EPA finally acknowledges unsafe levels of PFAS in “sewage sludge” fertilizers.

Organic and regenerative-organic agriculture and the importance of organic fertilizer

Scientific research proves the benefits and importance of organic fertilizers. As reported by Beyond Pesticides for example, a July 2024 study in Biology and Fertility of Soils highlights the benefits of organic farming for soil health, showing it restores ecological functions degraded by chemical-intensive practices. Organic fertilizers boost beneficial protistan predators and maintain sustainable predator-prey dynamics in the soil microbiome. In contrast, chemical fertilizers disrupt these relationships, reinforcing the case for transitioning to organic agriculture.

In addition to supporting a healthy soil ecosystem, Beyond Pesticides continues to issue a clarion call for ending the use of petrochemical pesticides and synthetic fertilizers and to accelerate the transition to organic farming. Organic agriculture and land management are essential to mitigating the existential threats of the climate crisis. Under organic management, healthy soil can absorb and store 1,000 pounds of carbon per acre foot of soil annually, translating to approximately 3,500 pounds of carbon dioxide per acre drawn down from the air and sequestered into the soil. [A fact often overlooked by policy makers in generating climate strategies or members of the public seeking to fight climate change is that carbon-sequestering soil practices are federally mandated in certified organic agriculture.]

The challenge lies in overcoming entrenched economic interests in the petroleum and chemical industries that perpetuate chemical-intensive farming and land management practices. Beyond Pesticides advocates for national grassroots collaboration to reframe public discourse and advance systemic change through organic land management. The organic approach operates on the precautionary principle, rejecting toxic chemicals in favor of sustainable methods to meet agricultural and landscaping goals.

The focus on soil health is a basic principle in organic agriculture that directly applies to all land management, including organic lawn and landscape care. See Beyond Pesticides’ website to learn about lawns and landscapes, hazards in common lawn pesticides, and safer alternatives, including organically compatible fertilizers. Please visit the Tools for Change page to learn how to organize your community to end pesticide use and adopt organic land care.

You can contribute to this transition by choosing certified organic food, supporting local organic farmers at markets, and practicing organic land care. Join Beyond Pesticides in fighting to protect the importance of organic integrity—and why public engagement is needed to ensure the National Organic Standards Board upholds strict rules regulating organic agriculture.

Join us in taking action on organic integrity by clicking here and see here for more topics for action.

All unattributed positions and opinions in this piece are those of Beyond Pesticides.

Sources:

Microbial biofertilizers and algae-based biostimulant affect fruit yield characteristics of organic processing tomato, Journal of the Science of Food and Agriculture, published on behalf of Society of Chemical Industry, August 31, 2024

Researchers stunned by results after utilizing unconventional farming tactic: ‘We were fascinated’, The Cool Down, November 6, 2024

Meta‐analysis reveals globally sourced commercial mycorrhizal inoculants fall short, New Phytologist, November 21, 2024

Researchers make stunning discovery after examining farmland treated only with organic fertilizers for decades: ‘[Will] help us to move forward’, The Cool Down, October 13, 2024

Microbial biofertilizers and algae-based biostimulants found to boost tomato crop yield and quality, Phys.org, Society of Chemical Industry, October 1, 2024

Plant Biostimulants: Definition and Overview of Categories and Effects, University of Florida Institute of Food and Agricultural Sciences (IFAS) publication, May 2019

Biostimulants 101, Small Farm Sustainability Iowa State University Extension

Lawsuit Targets Scotts Miracle-Gro for Claiming PFAS-Tainted Products Are “Eco-Friendly” and “Sustainable,” Beyond Pesticides Daily News, October 10, 2024

Study Shows Value of Soil Microbiome, Nurtured in Organic Farming, Harmed by Chemical-Intensive Ag, Beyond Pesticides Daily News, August 9, 2024