Harvest is around the corner and soon slow-motion videos of shakers working in orchards will flood your social feed. These awe-inspiring shots sometimes come with a price - Barking (when the bark tears away from the tree). The main reason for it is that trees are too "wet" carrying excess moisture in their trunks which makes them susceptible to damage during shaking.
A window of opportunity
The solution and common practice many growers in the Valley are using is to dry out their trees before shaking them.
But exactly how much time and how much stress should growers apply without affecting the tree's future health and productivity? When is the optimal time to cut irrigation and push the trees into negative growth and how much time should they stay thirsty?
This is where millions of plant pulses that we collect each day together with field feedback from our growers - came in handy.
By cross-checking direct data from the blocks (trees' trunk size and water demand, actual water delivery, and block's stress history) with information supplied by our customers (Actual barking rates in their fields) we have identified an irrigation practice that can significantly reduce this unwanted phenomenon.
We found out that avoiding positive growth 3 days before shaking significantly reduces shaker damage and helps in optimizing this stage. Cutting irrigation, inducing stress (red plant status), and stopping trees' growth 3 days before shaking can lead to "zero barking" and better rate of nut removal.
Supporting Evidence
This practice is also supported by a research conducted by a UC Davis team led by Prof. Ken Shackel who has used our dendrometers to measure day-to-day trunk growth.
"A reduction in trunk growth before shaking may decrease the susceptibility of the trees to shaker injury", wrote the researchers, "Nine trees were given excess irrigation before harvest. They maintained trunk growth, and 8/9 were damaged by the shaker. Only 3 trees in the standard (control) treatment were damaged". (Lysimeter –Whole Tree ET Response to Mild and Moderate Water Stress, Shackel et. al 2019)
Back on the growth track
After shaking, it is super important to get the trees back on the positive growth track to maintain their health and future productivity. Again, this is where seeing the trees' real-time response to irrigation allows our customers a quick response, supplying water according to the trees' water demand.