Making Sense of Biologicals: Biofertilizers Designed to Make Roots ‘Happy’

Tacy CalliesBiologicals, MSOB


“If mama ain’t happy, ain’t nobody happy.”

That same mindset can also be applied to agriculture. If the roots of a plant are not happy, the top of the plant won’t be happy either. Anything else will prove to be futile, believes Mark Egan.

Egan, an agronomist at Douglas Plant Health, says biofertilizers are a management tactic that growers can implement to make root systems more proficient in taking up nutrients. If roots serve as the lifeline of the plant, why wouldn’t growers want to ensure that lifeline thrives and remains fully functional throughout the production season?

“The primary purpose of biofertilizers is to make roots as healthy as possible, thereby enabling plants to be more resistant to whatever stresses come down the pike,” Egan says.

Those stresses are inevitable every season, especially for growers still trying to overcome citrus greening disease. The disease has devastated the citrus industry in Florida for almost two decades. While researchers continue to study this debilitating disease from different angles, the use of biofertilizers could be another tool in the grower toolbox.

“In citrus, you’ve got a plant with a compromised vascular system,” says Egan. When there’s a shortage of energy in the root zone due to greening, biofertilizers can add more energy to the soil for microbial conversion, he explains.

Biofertilizers are part of the biologicals sector in agriculture which represent a group of products derived from living organisms. Biofertilizers contain microorganisms, and if added to the soil, they can enhance fertility and promote plant growth.

A common biofertilizer is rhizobium, a symbiotic nitrogen-fixing bacterium familiar to farmers who produce legumes.

In organic production, there’s mycorrhizal fungi, which can form a symbiotic relationship with plant roots to effectively extend their root systems.

Internationally, biofertilizers are known to improve or increase the nutrient supply to plants.

“Through whatever fertilization practice you use, synthetic or otherwise, if it results in greater accumulation of carbon in the soil, you have, at least according to the Natural Resources Conservation Service definition, improved the soil health,” Egan says. “The way to improve soil health is to get more carbon into the soil, both temporarily and long term.”

Douglas Plant Health has many products that can be used on specialty fruit, including Residuce Complete and SP-1. Residuce Complete contains soil-conditioning humates that improve the vigor of the roots. SP-1 improves germination, water use and fertilizer efficiency. Both biofertilizers aid in root development.

“If you think about what’s going to happen to the root system of a crop whose vascular system above ground is compromised, its capacity has decreased,” says Egan. “Obviously, if the pipes are now smaller or there’s fewer of them, then the ability of the plant to do much below ground is reduced. Then the ability of the root system to support the rhizosphere is reduced.”

There are natural materials that can accelerate the rhizosphere, or the soil region in the plant roots’ vicinity in which the chemistry and microbiology is influenced by various factors, including growth and nutrient exchange. Biofertilizers enhance these natural processes.

“We’re simply trying to allow the good things that Mother Nature does to occur more quickly and more reliably,” Egan says.

While biofertilizers’ main objective is to improve soil health, they can also be used in conjunction with compost to break nutrients down faster.

Egan says that in the last few years he has seen an awakening in concern for citrus root health. “As a result, the application of compost around the base of citrus plants has become very popular,” Egan notes. “Municipalities that are composting now have a market for all of their municipal composts. They’re going out to citrus groves. The benefits of the compost are obvious and have been talked about for centuries. Where the biofertilizers come in is that they can and do accelerate the process of the availability of compounds that the composts have. In turn, this improves the environment for root growth. If the roots get happier, the tops get happier.”

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Clint Thompson