How Biochar Supports Citrus Trees Affected by Greening

Citrus greening weakens a tree from the roots upward. As roots decline, the tree has more difficulty taking up the water and nutrients it needs to support leaves, fruit, and new growth.

Biochar cannot cure citrus greening. It can improve the soil environment around the remaining roots. Its porous structure helps soil retain water and nutrients, while its stable carbon becomes a lasting part of the root zone.

For homeowners and orchard owners managing affected trees, that soil-support role can be valuable.

Citrus greening makes water and nutrients harder to reach

Citrus greening, also called Huanglongbing or HLB, damages the fine roots responsible for absorbing water and nutrients. UF/IFAS reports that affected trees may lose 30–50% of their roots early in the disease. Root loss can exceed 70% once canopy decline becomes visible.¹

That smaller root system cannot explore as much soil. Water and fertilizer that move beyond the active root zone become harder for the tree to use.

Current citrus guidance emphasizes keeping water and nutrients consistently available around the remaining roots. Biochar can support that goal by helping the soil hold those resources longer.⁵

Biochar helps keep water near citrus roots

Biochar contains a network of pores that can take in and release moisture. When mixed into soil, it can increase the amount of water available to plants between rainfall or irrigation.

A large review of soil-water studies found that biochar increased plant-available water overall. The strongest responses occurred in coarse-textured soils, including soils with a high proportion of sand.²

This is relevant to many citrus-growing areas in Florida. Sandy soil drains quickly and may store less water within reach of roots. Adding biochar can give that soil more capacity to hold moisture.

For an HLB-affected tree with fewer functioning roots, a better-supplied root zone can help reduce the time the tree spends under water stress. Biochar does not replace irrigation, but it can help the soil make better use of the water it receives.

Biochar helps retain nitrogen and other nutrients

Plain biochar is not a fertilizer. Its role is to help the soil retain and manage nutrients supplied by fertilizer, compost, or other materials.

A review of field experiments found that biochar increased plant nitrogen uptake and reduced nitrogen leaching overall.³ In other words, more nitrogen entered plants while less moved below the active root zone.

Biochar can also increase the soil’s cation exchange capacity, or CEC. This describes the soil’s ability to hold positively charged nutrients such as calcium, potassium, and magnesium.

For citrus trees with limited root systems, retaining nutrients near active roots gives the tree more opportunity to use them. Biochar and fertilizer therefore perform different but complementary jobs: fertilizer supplies nutrients, while biochar helps keep them in the root zone.

Florida citrus trees showed stronger growth in carbon-rich soil

UF/IFAS researchers Arnold Schumann and Timothy Spann observed citrus trees growing where old burn piles had changed the soil.

The trees in the dark, carbon-rich areas had 67% more canopy volume than trees in nearby untreated soil. Soil carbon and CEC were both 4.5 times higher.⁴

The old burn piles had introduced ash and other materials in addition to carbonized biomass, so the observation was not a controlled test of a commercial biochar product. Even so, the differences demonstrate the value of a root zone that contains more stable carbon and holds nutrients more effectively.

The trees did not grow larger because biochar removed HLB. They grew in soil that was better able to support water, nutrients, and roots.

How biochar supports an affected tree

Biochar can contribute to citrus care in several connected ways:

• Water storage: Its pore structure can keep more moisture available between irrigation cycles.
• Nutrient retention: Its surfaces can retain nitrogen and other nutrients within reach of roots.
• Soil structure: Biochar adds lasting pore space for water, air, and root growth.
• Biological habitat: Its pores provide protected surfaces where soil microorganisms can live.
• Stable carbon: Biochar remains in soil much longer than materials that decompose quickly.

These benefits support the growing environment. They do not control the Asian citrus psyllid, remove the HLB bacterium, or restore roots already lost to the disease.

Using biochar in citrus soil

Biochar is most useful when it becomes part of the active root zone.

For a homeowner, that means placing it in the soil beneath the tree’s canopy, where irrigation water and feeder roots are concentrated. Follow the product’s application directions, avoid cutting major roots, and water the amended area thoroughly.

Biochar can be used alongside compost and fertilizer. Compost contributes organic matter and nutrients. Fertilizer supplies the elements the tree needs. Biochar helps the soil retain water and nutrients so roots have more opportunity to use them.

For an orchard, the same principle applies at a larger scale. Focus on the wetted root zone rather than spreading material where roots receive little water. Application should fit the grove’s irrigation system, soil testing, leaf analysis, and existing fertility program.

Do not automatically reduce irrigation or fertilizer when biochar is added. Watch soil moisture and tree performance first, then make informed adjustments.

Better soil can help a stressed tree

Biochar is not a citrus-greening treatment. It is a tool for improving the soil around a tree whose roots are already under pressure.

That distinction does not make the soil benefit less important. HLB-affected trees need reliable access to water and balanced nutrition. Biochar can help sandy soil hold both, add durable structure to the root zone, and support the conditions citrus trees need for continued growth.

Explore Wakefield BioChar for agriculture for product options and application planning.

References

1. Dewdney, M. M., Vashisth, T., and Diepenbrock, L.; UF/IFAS Extension. 2026–2029 Florida Citrus Production Guide: Huanglongbing (Citrus Greening) University of Florida 2026. Current guidance on HLB symptoms, root loss, psyllid management, nutrition, irrigation, tree removal, and integrated grove management. Biochar is not presented as a cure or disease-control treatment. View Source ↩

2. Edeh, I. G., Mašek, O., and Buss, W.. A Meta-Analysis on Biochar’s Effects on Soil Water Properties—New Insights and Future Research Challenges Science of the Total Environment, 714, 136857 2020. Biochar increased plant-available water overall, with stronger responses in coarse-textured soils. Results varied with soil, biochar, application, and study conditions; the finding does not establish a fixed irrigation saving. View Source ↩

3. Zhang, Q., et al.. Effects of Biochar Application on Soil Nitrogen Transformation, Microbial Functional Genes, Enzyme Activity, and Plant Nitrogen Uptake: A Meta-Analysis of Field Studies GCB Bioenergy, 13, 1859–1873 2021. Field-study meta-analysis found greater plant nitrogen uptake and less nitrogen leaching overall. Responses varied with soil, biochar, and time; this does not establish a citrus-specific fertilizer reduction. View Source ↩

4. Schumann, A., and Spann, T.. Opportunities for Biochar Production and Use in Florida Citrus Citrus Industry; UF/IFAS Citrus Research and Education Center 2012. Researchers observed 67% greater canopy volume and 4.5-times-higher soil carbon and cation exchange capacity in burn-pile-affected soil. The comparison was observational and did not test a commercial biochar application or demonstrate HLB treatment. View Source ↩

5. Vashisth, T., Kadyampakeni, D., and Burrow, J.; UF/IFAS Extension. Nutrition and Irrigation Management for Florida HLB-Affected Trees University of Florida 2020. Explains how frequent irrigation, balanced nutrition, soil pH, and testing can support affected trees without eliminating the infection. View Source ↩