AlmondWise: Manage Crop Development with Tissue Sampling

As almond bloom comes to a close, leaves begin to push, indicating that another season is underway.  At this point what’s done is done for bloom in terms of weather and pollination, so now we’re tasked with managing crop development as best we can. Sampling should be our first consideration as soon as leaves reach their full size.

This is done to guide our fertility plan for the season. For example, if a tissue sample reveals a nutrient deficiency, we can add a foliar nutritional to an upcoming fungicide application. This is the best way to apply critical in-season nutrients. Soil conditions may be such that nutrients aren’t available to the plant. Foliar application is a highly efficient way to deliver key nutrients, particularly those with limited mobility that are only needed in small amounts.. Tissue testing is also the closest indication of the plant’s nutrient status, and can be a way to determine the nutrient levels needed in the soil and whether any adjustments need to be made there.  

During the post-petal fall period as almond leaves are emerging, the fruit is rapidly undergoing development. Water and nutrient status should be as close to optimum as possible since this is where size and weight of the nuts are determined. A few key nutrients for the almond crop are worth mentioning: 

• Nitrogen is likely the most yield-limiting nutrient, and after yield estimates for the current season are considered, a seasonal plan should be adjusted based on the tree status to avoid over- or under-application.
• Potassium is another important nutrient in almonds and can typically fall short of the crop’s needs if a sufficient pool isn’t maintained in the soil. At around thirty days after bloom, there is an increased rate of uptake by the tree, with the highest rate of uptake being 100 days after bloom. It’s a good idea to go over the field history with a crop advisor of choice to determine the best plan of attack for maintaining this nutrient, including the clay content of the soil and any past soil and tissue reports and application records. Similar to nitrogen, leaf sampling can guide in-season applications. 
• Boron and zinc are both critical micronutrients for the almond crop. Boron is steadily taken up by the plant as the season progresses; however, most is removed with the export of the almond hulls. Applications are often needed, especially when the almond fruit are inactive after hull-split, making post-harvest applications ideal for helping the tree store this nutrient for next season.
• Finally, zinc is likely the most commonly applied micronutrient in many crops, and almonds are no exception. Though zinc is used in small quantities, it is needed throughout the crop development cycle for numerous physiological processes. What makes zinc challenging to manage is its lack of mobility in both the soil and the plant. This requires both soil and foliar applications as needed according to leaf sample reports.

Other nutrients may be needed as well, but we should let tissue sampling be our guide to efficiently and affordably apply what is needed. Proper sampling and record keeping can be the difference between simply fertilizing and managing overall fertility, and with good integrated pest management, offer the best chances at sustainable yields.