Making Sense of Biologicals – Biofertilizers: Improving Nutrition in Citrus Trees

Tacy Callies MSOB, Nutrition


Citrus greening disease appears to be a problem for the foreseeable future for Florida growers. But what if growers could improve nutrition so trees could better cope with the disease? Scientists at Douglas Plant Health believe biofertilizers have that capability.

“Think about it from a human health standpoint,” says Marcus Jones, vice president of research and development at Douglas Plant Health. “You can have all kinds of pills and antibiotics to treat a disease, but emerging medical consensus considers good nutrition as one of the keys to preventing disease. The same holds true for crops and plants. Adding good nutrition and soil biology into your IPM (integrated pest management) program is often overlooked. We’ve gotten so used to managing pests and diseases, but we neglect the mineral nutrient aspect.”

In a research study, agronomists at Douglas Plant Health studied the effect that SP-1, a biofertilizer, combined with OBS, a biostimulant, had on soil health in a citrus grove. The soil was sandy with low organic manner.

“By adding mineral nutrition to our IPM program, we found significant root growth, improved soil structure and increased nutrient uptake,” Jones says. Pending further research, the findings could potentially have a lasting impact.

In the study, scientists noticed there was greater uptake from the roots to the shoots of zinc, manganese and calcium. “We see it clear as day in the untreated trees,” Jones says. “Nutrients are staying there in the roots. In the treated trees, you see nutrient movement from the roots into the shoots.”

He adds that because psyllid control has been such a struggle, focusing on improved nutrition is one alternative in the greening battle. “If we can protect the plant and make the plant healthier, improve the nutrition from the roots all the way up through the trees, we can provide tree health for growers and keep them in business,” Jones says.

Mineral nutrition is a focal point of biofertilizer inclusion in a grower’s IPM system. If growers strengthen citrus tree health, plants will better be able to stand up to diseases like citrus greening and greasy spot.

“If the tissues of a plant are deficient in calcium, manganese and/or copper, those tissues are now far more susceptible to a successful infection,” explains Mark Egan, agronomist with Douglas Plant Health. “The linkage to mineral nutrition is to ensure that trees are not deficient in copper, manganese and calcium … Deficiencies make disease more virulent.”

Jones describes IPM as using available resources (pesticides, fungicides, herbicides, etc.) in a manner that is environmentally safe yet able to effectively manage pests and diseases. “We’ve got to preserve what we have,” he says. “By responsibly using these resources, we can actually prolong the life of some of the solutions that have worked.”

Biofertilizers can help prolong the lifespan of some of the tools in the toolbox. The key is protecting the crop. There is a direct link between product quality and mineral nutrition. Biofertilizers provide added support for the overall nutrition of citrus trees.

“We don’t advocate that a farmer rush in straight away and reduce the amount of fertilizer they’re using. But in so many places in the country there are restrictions on the amount of phosphorous fertilizer you can use on a given crop or restrictions on the amount of nitrogen fertilizer you can apply to a crop,” Egan said. “Where biofertilizers can ultimately be a real benefit is by maintaining production levels with reduced input rates and by creating a situation in the rhizosphere where more of what is in the soil becomes available to the plant.”

Biofertilizers improve soils long term, increase nutrient availability, and create more opportunities for nutrient uptake.

“The main impact with the use of a biofertilizer has been a dramatic increase in the volume and new growth of root tissue. That has a huge impact on calcium and manganese, two of the things that are directly linked to so many diseases,” Egan concludes.

Visit to learn more about biofertilizers or call 815-872-1190 to speak with an expert agronomist.

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Clint Thompson