By Juanita Popenoe, Commercial Fruit Extension Agent
When should you fertilize southern highbush blueberries? UF researchers wanted to find out the best time to apply fertilizer so that nutrients were not lost to the environment. The shallow root zone on sandy soils, and the extensive use of fertigation in Florida means the risk for leaching is high. Blueberries utilize fertilizer differently at different growth stages, but little was known about southern highbush blueberries, which differ from their northern counterparts by not requiring as much chilling and growing at different times of the year.
Researchers looked at fertilizer use with one-year-old containerized southern highbush blueberries (SHB) grown in pine-bark amended soil. They followed the uptake and movement of applied fertilizer by using radioactively labeled nitrogen. In the first year ‘Emerald’ plants were treated once in late winter, four times during the growing season, and once in the fall. Treatments were applied based on plant growth stages in the second year.
They found that in the first year after planting, growth of all plant parts occurred mainly in the summer and fall. In the second year, stem dry weight increased rapidly with vegetative growth flushes while root growth was primarily in the fall. Based on this work, spring fertilization requirements of young SHB are minimal. In the first year plants were small with undeveloped roots in the spring. In the second year spring growth was supported by remobilization of stored root and stem nitrogen. Nitrogen uptake was most efficient when fertilizer is applied from summer through early fall.
The full article can be found at: Nitrogen Uptake and Allocation at Different Growth Stages of Young Southern Highbush Blueberry Plants. HortScience 52(6):905-909. 2017. By: Y. Fang, J. Williamson, R. Darnell, Y. Li, and G. Liu.
Photo credit: https://i.ytimg.com/vi/LrI-EkVBnoE/maxresdefault.jpg