June in the San Joaquin Valley marks the final few weeks before hull split in our early varieties. Opening up almonds, we can see that the nuts have turned opaque white and there is no residual clear gel. It’s a great time to analyze size and see the rewards of tightly managing irrigations to improve nut development.
Looking back, we’ve had a relatively moderate season but it is picking up and so are the trees. With the persistent winds and the more recent increase in temperatures and day length, we’ve had to step up irrigations to meet crop requirements.
For the next three to five weeks, growers will be working carefully to manage irrigations and maintain available water throughout the root profile. By optimizing available water, we can maintain our crop weight, quality and overall tree health going into hull split.
A big concern for growers right now is losing their deeper moisture within the trees. To maintain available water down to 36”, we have had to step up the length of irrigations and even tightened up the frequency.
Fields that received 24 hours weekly have doubled in demand within the last 45 days and are now at 36 to 48 hour sets one to two times per week.
With aggressive root pull throughout the 36” root zone, a 24-hour irrigation just isn’t cutting it. In the below example, we can see where 36 and even 48-hour irrigations have been needed to drive water down to 36”.
On May 24, my recommendation to run 24 hours in this field did nothing more than to drive the 18”sensor down.
By June 1, we made it a point to run this field for no less than 48 hours. This irrigation was able to push water down to 36” without leaching past the root zone. In our schedule, we have another 48-hour irrigation planned for June 8 to drive water down to 36” and maintain the tension in the lower part of the comfort zone as a proactive measure to have deeper moisture before hull split.
As the demand of water in each field increases we have also seen some soils begin to reject water. In the above example, we were able to effectively run a 48-hour irrigation without runoff but in other fields we are handicapped by the current soil chemistry and structure causing infiltration issues.
Water infiltration has slowly decreased in almost every field but some are in dire need of surfactants to improve water penetration. Soil chemistry is a huge factor right now because the gypsum that was applied in winter has been depleted and salts are beginning to accumulate. With hydrophobic soils, we have seen water running off to the end rows without percolating as much as 12″ (see photo of an orchard with infiltration issues at right).
To combat this growers have added water surfactants to improve infiltration. Gypsum injection has greatly improved infiltration issues in fields most growers would have written off for the season. By staying on top of these fields, we have been able reduce standing water in these orchards and improved percolation down to the deeper soil horizons.
By optimizing available water, we can maintain our crop weight, quality and overall tree health going into hull split. By maintaining optimal tension levels in June we can transition healthy trees into our deficit irrigation regiment to finish out our crop.
This ease in transition will help improving crop uniformity during harvest as well as reduce tree damage from broken limbs prior to harvest. For more questions on summer irrigations, please contact your local irrigation management advisor.
About the Author
Irrigation Management Advisor Travis Goldman was born and raised in Watsonville and currently provides irrigation scheduling services to growers in California’s Central Valley. He graduated from UC Davis and has worked throughout California as a service technician, grower support specialist and irrigation management advisor to learn and understand every aspect of Hortau’s irrigation management platform.