Almond nutrient management expert Patrick Brown spoke at The Almond Conference 2019 about the importance of properly timing one's nitrogen applications, reminding growers that it does no good to load up the soil with nutrients until the trees are ready for uptake.
(March 6, 2020) – Nitrogen invigorates almond trees and is necessary for fruit growth and development. But how can growers to know how much nitrogen to apply, when it should be applied and how best to apply it?
Answers to those questions will be the focus of a two-part “In the Orchard” series on nitrogen management, and in this article – part one – we’ll discuss basic information all growers should know about nitrogen management.
Remember the 4 R’s
Experts say that efficient nitrogen management can be best expressed by talking about “the four R’s:”
- Right rate: Match supply with tree demand from all inputs (fertilizer, organic nitrogen, water and soil)
- Right time: Application must coincide with tree demand and root uptake
- Right place: Application must be delivered to active roots, not below the root zone
- Right source: Maximize uptake and tree response and minimize waste
“The four R’s are specific to every orchard, every year,” said Sebastian Saa, senior manager of Agricultural Research for the Almond Board. “No two orchards are identical.”
Some experts also mention a fifth “R” – right monitoring. Leaf analysis, sap analysis, trunk measurements, carbohydrate analysis and soil nutrient status all are ways growers can best understand the needs of their trees and manage nitrogen more efficiently.
“Monitoring is the key to managing,” Steve Petrie, director of Agronomic Services for Yara North America, told attendees of The Almond Conference (TAC) 2019 in December.
Recent research funded by ABC suggests that conducting leaf sampling earlier in the season can lead to more actionable results. Experts say growers can begin to estimate their crop’s nitrogen demand as early as January, based on a five-year average of previous yields and fruit set.
In addition, ABC’s California Almond Sustainability Program (CASP) includes a Nitrogen Budgeting Calculator that allows growers to input data specific to their orchard and receive a total nitrogen fertilizer recommendation, along with recommended application amounts that are calculated by the stage of crop growth. The calculator, along with ABC’s Nitrogen Budgeting Tool, also provides growers with the proper paperwork they need to submit nitrogen budgets to their local Irrigated Lands Regulatory Program coalition.
Timing is key
Until the trees are ready for uptake, it does no good to load up the soil with nutrients, according to UC Davis’ Patrick Brown, who is an expert on almond nutrient management. Brown said that trees must have at least 70% of their leaves before fertilizing is effective.
“The ideal time to fertilize is from 70% leaf-out through early July,” Brown said at TAC 2019.
Multiple applications are necessary to properly nourish a tree, too. About a third of the nitrogen needed throughout the growing season should be applied between 70% leaf-out and spur leaf expansion, Brown explained. Another 24% of total nitrogen should be applied between spur leaf expansion and kernel fill, and then 22% between kernel fill and shell hardening.
Smaller applications can also be made during harvest.
“You can fertilize during hullsplit, but if you do it’s not recommended that you apply a lot,” said Brown.
Brown said a standard annual application rate for nitrogen is 68 pounds per 1,000 pounds in yield, but that “more isn’t better.”
“If you’ve overfertilized, you should eliminate the post-harvest application,” he said.
Growers may view the slides presented at the TAC 2019 session on nutrient management by clicking this link: Research Update: Nutrient Management.
Next week: Steps growers can take to efficiently manage nitrogen.
