Root physiology

We are investigating the impacts of pruning and irrigation practices on root growth dynamics in walnut.

Mini-rhizotron tube installation

Root growth is tracked throughout the season using a mini-rhizotron camera.

Clear acrylic tubes 55 inches in length were installed in the berm 2 feet from the tree. This is accomplished by driving a steel soil sampling tube into the berm using a slide hammer attachment. The sampling tube is held in a guide frame angled at 45 degrees. The acrylic tube is then installed leaving approximately 9 inches exposed above the soil.

This configuration allows for photos to be collected over a total depth of 3 feet.

Mini-rhizotron tubes

The camera is attached to the top of the tube through an indexing hole to avoid rotation during data collection. An incremented indexing handle is used so that the camera position for each photo is uniform from one data collection to the next.

Photos below display a sequence over time of the same root section.

Root excavation of unpruned Chandler walnut tree.

Root excavation of minimally pruned Chandler walnut tree.

Publications

Contador, Maria Loreto, Louise H. Comas, Samuel G. Metcalf, William L. Stewart, Ignacio Porris Gomez, Claudia Negron, Bruce D. Lampinen, 2015. Root growth dynamics linked to aboveground growth in walnuts Juglans regia L. Ann. Bot. 116: 49-60.