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Proper planning ensures optimization of post-harvest almond nutrition  

Harvest 2024 is approaching rapidly. As an advisor to growers, the period leading up to and following harvest is a critical time of the year. Fertility plans to finish the growing season need to be developed and shared with growers. This means developing a plan for providing the nutritional elements to crops that are essential to ensure a healthy, robust start to the 2025 growing season. Some key questions deserve significant consideration during this time:

1. How much over or under was the crop in relation to our nutrient budget?
2. What are my actual N, P, K, B and Zn needs?
3. When will harvest be completed and when can these be applied?
4. What combination of products and processes will ensure maximum crop uptake of these essential elements?

Taking time to think through these questions is essential to executing a successful program that will set the stage for next year. Every grower is different, and field-to-field variability ensures that running a “cookie cutter” program out to every grower is not the ideal way to address the nutritional status of your crops. There can also be a high degree of variability in expected nutrient demand between pre-season planning and yield-driven actuals. For example – the 2024 Objective Almond Estimate for yield is 13% higher than the 2023 estimate. If you are anticipating a yield increase over last year, are you adjusting your budget to account for a larger crop?

Every successful post-harvest crop nutrition plan is based on assumptions. The timing of harvest and the lag between the removal of the crop from the field and the processing of the crop creates a scenario where growers and advisors often have to operate on a yield value that is not exact. Understanding actual crop demand for nitrogen during this period is critical. If we assume a nitrogen use efficiency of 80% and a 2500/lb acre yield, actual nitrogen demand is approximately 5-10 lbs/acre between mid-August and mid-September. Common practices on post-harvest fertilizer usually see a much higher application rate, usually in the range of 20-40 lbs of nitrogen applied per acre. Excess nitrogen in the soil solution can actually reduce transpiration rate of the plant by increasing the osmotic potential of the soil water solution. In plain English, this means that plant water uptake can suffer as a result of applying too much nitrogen in one application. This is especially critical in crops like almonds where water demand far exceeds water applied in the period leading up to and directly following harvest. When trees have reduced transpirational capacity, this leads to a reduction of water uptake and the nutrients that you are applying with that irrigation water. Ensuring sufficient supply and uptake of critical mineral nutrients like nitrogen, phosphorus, potassium, calcium, zinc and boron is especially critical at this time of year.

Timing is also of critical importance. Typically, between mid-August and mid-September, we still have bud differentiation taking place and we have the capacity to influence optimal bud set. But as daylight hours get shorter and shorter from late September into October, transpirational activity of plants is ultimately reduced. This has a direct effect on uptake efficiency for the critical elements that need to be provided to your crop. Inadequate storage of carbohydrate and nutrient reserves post-harvest can be a significant limiting factor on yield potential the following season. We are best served if we can avoid that situation altogether.

How do we address this?

There are several key steps you can take to ensure the success of a post-harvest fertility application.

First – Match application rates with demand as closely as possible. Getting a jump on nutrient applications as soon as possible after harvest is critical. For growers with multiple varieties in the field where split-set irrigation is used, don’t hesitate to apply fertilizers to varieties that have already been harvested. Also, consider making several applications of fertilizer through the irrigation system if water availability is good. Try to have applications completed before the end of October to ensure maximum crop uptake and minimize drawing on stored nutrient reserves already in the plant.

Second – Utilize fertilizers that are readily available for immediate uptake. Focusing on ammoniacal and nitrate sources of nitrogen is key. Because of reduced biological activity in the soil due to dry conditions, assuming that urea will remain in the soil profile and convert to soluble nitrogen is a risky proposition. YaraLiva^® CAN-17™ and YaraLiva^® CN-9^® are ideal choices not just because of the nitrogen forms present, but because the nitrate nitrogen assists in the uptake of other key cations like potassium and zinc. Additionally, soluble calcium uptake helps crops withstand the drought stress that all almond orchards undergo during deficit irrigation. Post-harvest recovery is what is needed, and these products will help bring your crops back up to the condition they need to be in to ensure they go into the dormant season fully charged.

Third – Explore options for blending. While YaraLiva CAN-17 and CN-9 are not commonly blended with other products today, there are tank mix options in the market that allow you to combine other essential elements with the soluble calcium found in YaraLiva products. Utilizing a water-run post-harvest fertility program featuring YaraLiva products reduces or eliminates the need for a post-harvest foliar application. Saving your growers the hassle of taking out the sprayer and making a foliar application is an option that has a lot of appeal to growers who are finishing out the season.

Contact your local Yara representative to discuss how to address post-harvest nutrition.