Plant Water Potential of Southern Highbush Blueberries (Vaccinium corymbosum hybrid) Grown in Different Pine Bark Amended Soils

Southern highbush (SHB) blueberries (Vaccinium corymbosum hybrid) require acidic soils that are well- drained and have high organic matter content. However, very few soils in Florida are suited for blueberry production without significant modification; as a result, blueberries are commonly planted on pine bark beds that are 15 to 18 cm high and approximately 1 meter wide. This system may use up to 1,000 to 1,200 cubic meters per hectare of pine bark at a cost that can exceed $9,500 per hectare. Physical and chemical characteristics of pine bark vary with age and level of decomposition. Commercial production systems using pine bark beds typically require more frequent irrigation than systems where plants are established directly in soil. Water management on pine bark beds is further complicated because blueberry roots are typically confined to the pine bark layer. The objective of this study was to evaluate drought susceptibility of SHB on several soil management systems during a dry period without irrigation. Predawn and solar noon plant water potential of ‘Emerald’ SHB was measured with a pressure chamber during a 25-day period in which no irrigation was applied.  Four soil management systems were evaluated: 1) Non-amended soil (NAS); 2) Eight cm of pine bark incorporated into the top 15 cm of soil (8 PBI); 3) Eight cm of pine bark incorporated into the top 15 cm of soil plus 8 cm of pine bark mulch (8 PBI+8M); and 4) Fifteen cm pine bark layer on top of non-amended soil (15 PBL). During the last week of the experiment differences were observed among treatments. The non-amended soil showed higher predawn plant water potential than ‘8 PBI+8M’ and ‘15 PBL’. No differences were found at predawn between ‘NAS’ and ‘8 PBI’. No differences among treatments were observed in plant water potential at solar noon. The results suggest that SHB on highly amended soils may be more susceptible to prolonged droughts than SHB on non-amended soils.