• Plant Nutrition
  • Aug 23, 2021

Enhance Fall Fertility With Micronutrients

WinField United grower examines soil while planning fall fertility program.
Fall nutrient applications are one of the very first steps you’ll take in managing next year’s crop. You’re likely planning to apply phosphorus, potassium and maybe even sulfur, but what about the micronutrients critical to plant performance? There are many instances where fall-applied micronutrients can benefit not only the coming year’s crop, but your operational efficiency as well.   

The Role of Fall-Applied Micronutrients

Micronutrients are often applied via foliar applications in-season, but they also have an important role to play in soil-applied fall nutrient mixes. Post-harvest applications help provide a baseline of key micronutrients for the crop coming in the spring.
You may be thinking, “But don’t micronutrients get tied up in the soil when soil-applied ahead of time?” Since most micronutrients exist as positive cations and soil is negatively charged, that can be true for a portion of the application but there’s still benefit in establishing a baseline in the fall. If your soil is substantially deficient in certain micronutrients, foliar applications in-season may not be enough to fix the problem.
By providing a supply of micronutrients from the start, you’ll help protect your crop from deficiency stress before it becomes a detrimental issue. Having a baseline of micronutrients in the soil may allow your crop roots to take advantage of nutrient uptake through mass flow, diffusion and root interception. This baseline application can be partnered with an in-season tissue sample to help you catch and fix an issue more quickly with more minimal yield losses. In addition, by making these applications in the fall, you can streamline your passes by simply adding it to your planned application. Oftentimes, it’s even found that fields with a history of deficiency no longer experience fundamental in-season micronutrient deficiency, thus reducing potential foliar application needs.

How to Determine Micronutrient Needs

When evaluating micronutrient levels in-season, it’s always best to take a tissue sample and follow the report’s recommendations. However, the situation is different once the crop is gone. Sometimes, a post-harvest soil sample will tell part of the story, but it doesn’t provide all the information needed. It’s only a snapshot of what’s available at that particular time and, at the time of a fall soil sample, the crop isn’t growing, so it doesn’t really matter what’s available.
What I typically recommend when evaluating micronutrient needs in the fall is to look at your soil and tissue sample trends from the past few years. For example, let’s say you’re always seeing zinc deficiencies, and you’re currently using a foliar zinc application in-season, but it never seems to be enough. That’s likely a sign your fields could benefit from the head start of a fall application.
I also recommend comparing yields to removal rates. Evaluate soil and tissue test history and then determine how much of your fields’ nutrients are being removed. If levels are low in the soil plus you had some great yields, it’s especially important to replace those lost nutrients. Remember, foliar applications only mend a small fraction of what the removal rate is. Be sure to check nutrient removal rates based on yield level as well.

Help Optimize Micronutrient Availability With Lignosulfonates

To help prevent micronutrient tie-up in situations like fall applications, we created a line of fertilizers containing lignosulfonate (LS) compounds derived from plant material that help protect micronutrients from being tied up in the soil. For example, many growers have found success mixing Zinc 10% LS into their dry phosphorus and potassium blends. Explore the full WinField United LS line: Adding micronutrients to your fall fertility pass is a great way to step up your nutrient game this fall. Work with your local WinField United retailer to determine the best strategy and products for your operation.
All photos are either the property of WinField United or used with permission.

© 2021 WinField United. Important: Before use always read and follow label instructions. Crop performance is dependent on several factors many of which are beyond the control of WinField United, including without limitation, soil type, pest pressures, agronomic practices and weather conditions. Growers are encouraged to consider data from multiple locations, over multiple years and to be mindful of how such agronomic conditions could impact results. WinField is a trademark of WinField United. All other trademarks are the property of their respective owners.

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