July/August 2024
Non-bearing almonds: What do younger trees really need in terms of water and nitrogen?
Non-bearing almonds, those that haven’t yet reached a fourth growing season, need proper nutrient and water management for success. During this time, these young trees undergo a major period of root growth and develop their basic framework.
The non-bearing stages are critical to the future productivity of the crop.
Cameron Zuber recently presented a session entitled, “Non-Bearing Almonds Water and Nutrient Management Principles” as part of The Young Orchard Irrigation and Nutrient Management workshop presented by The University of California Division of Agriculture & Natural Resources.
Zuber is a farm advisor for University of California Cooperative Extension (UCCE), covering Merced and Madera counties, and has been working with almonds in the San Joaquin Valley for a while, so he has a lot of knowledge surrounding this topic.
“The primary key points are to understand how the water- use requirement may be different between younger and older orchards, and the same thing as it pertains to nutrient requirements,” Zuber said. “Working within a perennial system, where a lot of management strategies are designed for older trees, we need to know how to work within that and adapt it to younger orchards.”
The presentation touched on fractionally how much less water younger trees really need at different times of their lives, and the same with nitrogen.
“There will also be a few nuances of what you can do — or what I’ve seen others do — to try and successfully bear young almonds when you are trying to have what ultimately will be 20 years of a healthy orchard,” Zuber said. “How to calculate the water use, how to apply it where they need it, and the same thing for nutrients with a focus on nitrogen.”
For water, the main thing almond growers need to know is younger trees use much less water.
“We see a plateau point around four to five years for almonds, and there’s a gradual increase from one to four years, so it’s a matter of understanding that particular variable for each year,” Zuber said. “It’s also a matter of delivery. You have to consider the type of irrigation you’re using that most likely was designed for larger orchards, so are there things you can plan for to better apply the water where trees need it.”
But what you do will ultimately come down to what a grower is looking for — do they want to be pushing yields right away, or to develop a good structure so trees will be less stressful when they get bigger?
“They must weigh the pros and cons of each approach, working within whatever system they chose,” Zuber said.
With nutrients, generally there are two ways of thinking when you’re dealing with nitrogen. One is the nitrogen going towards the growing wood and leaf material as well as when you hit a bearing age, accounting for the nutrient requirements before that.
“While there’s a simple fraction to account for off of harvested material, you can make an assumption of what the nitrogen demand is, but at ages 1,2, 3 and 4, bearing or non-bearing, it’s slightly different,” Zuber said. “The extra considerations you need to take into account include how much nitrogen is in your water, how much in the soil and whether that effects the total amount you are actually applying.”
Growers must understand what form nitrogen is taking and how it is applied.
“If it’s fertigation or inline drip, you can’t necessarily assume high levels of efficiency,” Zuber said. “There are things that can help.”
With harvest soil, one thing Zuber runs into a lot when doing prep, sometimes the soil the trees are planted into can be very open, and he’s seen issues where many die. “For the most part, the soil considerations are on how horizontal the water may be moving in the soil,” he said. “With sandier soil, it’s just a straight column down; with heavier soil, you might be able to have some lateral movement which can expands the wetting area, which could be a good or bad thing depending on the situation.”
There are chemical compositions in the soil that could impact some micronutrients.
“The difficult challenge is to make sure you get the water you want without having to use a lot of water,” Zuber said. “With micro-sprinklers, the tendency is to move it closer to the tree. The problem is, that can create disease issues if the trunk itself is getting wet.”
Therefore, if growers aren’t adapting the irrigation to fit where the tree can reach water, they are dealing with the challenge of giving them enough water when they need it.
“If you try to adapt the system to get the water where they are when they’re smaller, it can create disease issues as they get larger, so there’s no silver bullet,” Zuber said. “The challenges are based on the management strategy. It’s just a matter of being aware of it and accounting for it when you can.”
Zuber’s rule of thumb for water and nutrients is to figure out how much is needed, apply it and then check and make sure it’s working.
“If it’s not, it can inform you to adapt to it as necessary,” he said. “To test, (it) doesn’t have to be that technical. If you’re not checking that the response is what you expect, you don’t know if there is a deficiency or not. The best test is whatever tool integrates into your system the best.”
