By Tripti Vashisth, Abhishek Neupane and Taylor Livingston
Florida citrus trees are under pressure from huanglongbing (HLB). The disease weakens root systems, reducing the tree’s ability to take up water and nutrients. Compounding this issue, most Florida groves sit on sandy soils with very little organic matter. These soils drain quickly, struggle to hold nutrients and allow both water and fertilizer to move out the root zone. When roots are compromised and soils cannot retain resources, managing irrigation and fertilization becomes even more challenging.
Increasing the frequency of water and fertilizer applications has been shown to improve the yield of HLB-affected trees. However, multiple applications can be labor-intensive and challenging for grove management. Organic amendments such as compost and biochar can increase soil organic matter and improve the soil’s ability to hold both water and nutrients. While these materials do not cure HLB or restore lost roots, they can improve conditions around the remaining roots and help them function more efficiently, eventually leading to healthier trees.
Video by Michaela Ivy and Taylor Livingston
The above video demonstrates how the integration of compost alone or with biochar in sandy soil can slow down and reduce leaching of water and nutrients from the soil. In this demonstration, each column received 500 milliliters (mL) of liquid fertilizer. The sand‑only column began leaching almost immediately, releasing about 200 mL of solution. The sand‑plus‑compost column leached roughly 160 mL, while the compost‑and‑biochar mixture leached less than 150 mL.
Electrical conductivity measurements indicate that the sand‑only column loses the highest concentration of nutrients, the compost‑amended column leaches fewer nutrients, and the compost‑plus‑biochar column retains the most nutrients overall. The use of compost can help reduce water and nutrient deficits in trees, leading to healthier trees with better roots.
To further prove the effectiveness of compost and biochar, a University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) outdoor container study compared pure sandy soil with sand amended with compost and compost plus biochar at different rates. The differences in water behavior were clear. Increasing compost rates, particularly when combined with biochar, substantially improved soil water-holding capacity and slowed soil drying between irrigation events compared to sand alone (Figure 1).
These preliminary results suggest that building organic matter in sandy citrus soils can significantly improve both water and nutrient retention. For growers managing HLB-affected trees, practices that support root-zone conditions may help reduce water and nutrient losses and improve overall grove-management efficiency. Field validation is ongoing, but compost, particularly when paired with biochar, shows promise as part of a long-term soil health strategy in Florida citrus production.
Tripti Vashisth is associate center director and associate professor, Abhishek Neupane is a master’s student, and Taylor Livingston is a biological scientist — all at the UF/IFAS Citrus Research and Education Center in Lake Alfred.
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