Giancarlo Buzzi

Giancarlo Buzzi

Drench Applications of Humic Acids Do Not Improve Southern Highbush Blueberry Transplant in Soilless Substrates


Giancarlo Buzzi, Cecilia Heller, Gerardo H. Nunez


Dr. Gerardo Nunez


College of Agricultural and Life Sciences


Biostimulant use is increasingly popular in specialty crop production. Biostimulants elicit plant responses that can help prevent or mitigate plant stress. Humic acids are a biostimulant that has captured the interest of blueberry growers, but little is known about appropriate rates and specific effects in blueberry production. Previous observations suggests that humic acid applications promote blueberry growth, but quantitative assessment of plant responses is lacking. We hypothesized that humic acid application enhances root growth and increases blueberry transplant successes in soilless substrates. We tested this hypothesis in a greenhouse experiment with ‘Sweet Crisp’ southern highbush blueberry plants grown in rhizoboxes. The experiment had four treatments: a control (greenhouse water) and three humic acid drench applications at concentrations of 0.7%, 1.34%, and 2.4% v/v humic acids. Treatments were applied on a weekly basis for 10 weeks. We measured plant growth, root system characteristics, leachate electrical conductivity (EC) and pH, and substrate respiration. All plants received the same irrigation and fertigation. Higher humic application rates led to higher substrate respiration, but they decreased leaf area, total dry weight, and root convex hull area. Leachate from rhizoboxes that received higher humic acid concentrations exhibited higher pH and EC, which could be the reason for the limited plant growth observed in these treatments. Altogether, our results suggest that drench application of humic acids does not improve southern highbush blueberry establishment in soilless substrates.


Hover over the image below to zoom in or click to view full screen.

Research Pitch

View a 3-minute research pitch below.

To comment below, please sign in with Facebook or Google (using your ufl account) by clicking the little round icons to the right. If you decide, you can post as a guest by entering name and email below, but will lose some features. You can also subscribe to a students page to get updates on comments!


Leave a Reply