Hydraulic Properties of Pine Bark Amended Soil for Blueberries in Central Florida.

Blueberry is becoming an important crop in central Florida because of high fruit prices early in the spring. Blueberries require an acidic soil pH, and it is a common practice to amend central Florida ridge soils (e.g. Chandler fine sand with >95% sand) with pine bark. As a result, the hydraulic properties of the amended soil changes greatly. Irrigation requirements for this soil mixture are therefore not completely understood, and consequently growers may over irrigate. Adding pine bark to the sandy soil creates a mixed soil medium that varies spatially a great deal. Also, the composition of the soil mixture changes over time as the pine bark degrades in the warm and humid conditions. Additional pine bark is commonly added after 3 to 4 years to maintain correct soil conditions. To irrigate properly, it is necessary to understand the soil hydraulic properties of the amended soil and how this change over time. This report discusses observations made over a one year period. The average depth of the pine bark layer decreased from 20 to 15 cm in one year. Average bulk density of the pine bark amended soil in the 0 to 15-cm depth was 0.55 g cm-3 when measured in July 2008 and 0.62 g cm-3 in September 2009. Bulk density in the subsoil remained at 1.58 g cm-3. The field capacity water content measured in 2008 was 0.290 cm3 cm-3 and was ~ 0.225 cm3 cm-3 in 2009. The lowest water content the soil reached in the field was 0.090 cm3 cm-3. With these values, available water was calculated to be 0.200 in 2008 and 0.135 cm3 cm-3 in 2009. In non-amended Candler sand, field capacity water content is ~0.08 cm3 cm-3 and the driest it can reach in the field is ~0.02 cm3 cm-3 yielding an available water content of 0.06 cm3 cm-3.