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Sponsored: Foliar Timing and Temperature

Over the past year, agronomists have fielded as many questions about foliar fertilizers. The presumption is that some of this attention is because foliar applications were a component in the recipes used by recent national yield contest winners.

Another possible explanation is that with tight margins, farmers are looking for ways to cut costs while maintaining yields. Foliar fertilizers can be a useful tool if used in the right way with the right expectations.

Here are two things you should consider before applying:

  1. What are soil test levels? If soil tests show less than optimal macronutrient (N, P, K, S and Ca) levels, I recommend you start there and focus on improving your soil fertility.
  2. What is your limiting nutrient? Use soil and/or tissue testing to identify which nutrient(s) are scarce.

If you meet these two criteria you are on your way but there is one more important piece to the puzzle. When it comes to foliar applications, timing is everything. In 2016, Beck’s Practical Farm Research (PFR)® began conducting trials with the goal of determining the optimal time of day and/or temperature to apply a foliar fertilizer. Initial results show early morning applications are more beneficial than those made during the day. Testing from 2016 shows a 4.2 Bu./A. average advantage to making an application early in the morning versus the afternoon. When comparing how offensive and defensive hybrids respond to these timings we found early morning applications resulted in a 6.0 Bu./A. increase when applied to an offensive hybrid and a 2.4 Bu./A increase when applied to a defensive hybrid. Data from 2017 showed similar trends and is shown below. Click here to see additional research and data from Beck's PFR Program. 

5.8-Foliar Time and Temp

So, why is that? We know that before a foliar fertilizer can be utilized, it must enter the plant. The leaf does have porous openings called stomata. However, they aren’t always open and they are more plentiful on the underside of the leaf than on the top.

Furthermore, before fertilizers even reach the stomata, they must penetrate a thin waxy covering on the leaf surface called the cuticle. Stomatal movement is primarily influenced by light, temperature, and humidity, so we will continue to investigate what environmental conditions are most favorable for applying a foliar fertilizer.

In the meantime, if making a foliar nutrition application I recommend the following:

  1. Closely monitor moisture. If your crop is short on moisture, it will strive to preserve moisture by thickening the leaf cuticle and limiting how wide and how long stomata are open. This, in turn, impedes a foliar nutrient getting inside the plant.
  2. Make applications early in the morning or when conditions are warm (but not hot) and moist. This is when leaf tissue is most permeable.

Contact your trusted advisor if you have questions about applying foliar fertilizers or other ways you can improve profitability on your farm.


Beck’s PFR  is the largest source of unbiased, cutting-edge agronomic information in the industry. More than 500 studies were conducted in 2017, comparing over 150 products across multiple locations to learn how different management practices and new technologies perform in field environments. In evaluating agronomic practices and input products, not comparing seed products, Beck’s PFR aims to help farmers maximize their input dollars and increase their bottom line. To view more PFR studies click here  .


Practical Farm Research (PFR)® is a registered trademark of Beck’s Superior Hybrids Inc.  

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