We have been experiencing 7 days without rain. Irrigation/rain is critical during fruit sizing and for plant growth in blueberry. Looking at past weather data from the University of Georgia Weather Network, the Alma weather station had the largest amount of rainfall in the last 7 days (April 7, 0.01 inches was recorded over the 24 hour period). At an irrigation trial being conducted in Alapaha, we have been applying ¾” at week (0.11″ per day) to three year old rabbiteye and southern highbush. Our observations show that ¾ of an inch irrigation is sufficient for the southern highbush; however, the rabbiteyes are reading an average of 10.1 kPa or centibars over each 24 hour period. The highest reading was 16.7 kPa and the lowest was 5.0 kPa. The target for sandy soils is 10 kPa. Though the reading at 12″ did not exceeded 10 kPa over the average, the reading at 4″ were averaging 14.5 kPa. Soil moisture monitoring is critical as our weather pattern remains dry, especially for new plantings. Further, the forecast is predicting warmer to hot weather without any indication of rain.
Considering evapotranspiration (Et) for the last seven days, the averages for Alma, Alapaha, Baxley, Homerville, and Nahunta were 0.18, 0.17, 0.17, 0.16, 0.16, respectively. This means that a mature southern highbush or rabbiteye with a crop may not be receiving sufficient water at ¾” per week. Avoid falling into a water deficit, especially if you have only drip irrigation. At a minimum, apply 1 acre-inch a week (0.14 in per day), monitor soil moisture, and check your irrigation system for proper operation. Increase irrigation rates if soil moisture is not sufficient.
Monitor soil moisture at 4″ to 8″ depth for mature plants and 4″ for new and younger plantings. Take soil samples 4″ – 5″ to the left or right of the drip line. The easiest soil moisture monitoring method is the clod method. Squeeze a hand full of soil in your hand if water oozes out 75-100% moisture, sticks together 50-75%, forms a clod but crumbles easily 25-50%, and does not form a clod 0-25%. Irrigate at 50-75%. There are various soil moisture monitoring devises; choose one type, place them in similar soil structure, and use 10-15 kPa as the set point in sandy soils to irrigate.
