In conjunction with regular sprayer maintenance and calibration, using the TRV approach helps deliver the appropriate chemical load to leaf and fruit surfaces. Matching sprayer output to canopy volume results in effective chemical application and pest control, and can also produce significant cost savings.

In orchard spraying, chemicals are applied to trees, which are three-dimensional objects, rather than a two dimensional area of land. It seems logical therefore, that the three-dimensional volume of the canopy would be the basis for determining spray volume (gallons per acre) rather than the two-dimensional ground surface area of the orchard. The tree row volume (TRV) approach uses estimates of tree canopy volume to determine spray volume. Canopy volume depends on tree size and shape and between row spacing. Because different orchard blocks are configured differently, the TRV should be estimated on a block by block basis.

There are several variations on the tree row volume theme. Some approaches include a factor for canopy density. Others include a factor for the stage of growth that increases during the season until budset to allow for changes in canopy volume. Most allow you to adjust the volume to compensate for dilute versus concentrate spraying. Although these have been developed primarily in the eastern US and have not been validated under Mid-Columbia conditions, the basic concept seems very sound.

The following is one approach for using the TRV approach to determine spray volume. This particular method calculates optimal gallons per acre for a specific block configuration. That value can be used in the previous calibration method starting at step 4.

Step 1. Measure

a. Tree height

b. Tree width

Step 2. Decide tree shape

Step 3. Calculate target sprayer output (GPA) using the given formula.

Step 4. Complete calibration starting with #4 in the sprayer calibration section.