Agronomy Talk

Field News

Sulfur Nutrition and Deficiency

Published on Monday, June 12, 2017

We experienced quite the planting season this year with heavy rainfall events occurring in much of our marketing area, resulting in significant replant of corn and soybean acres. Though the decision-making process and additional work seemed difficult at times, your efforts were not lost. Most replant stands that I have evaluated are looking very good and progressing nicely toward the genetic and yield potential of each hybrid and variety. With that said, I wanted to share with you some observations I have made in respect to the sulfur (S) nutrition in many of the fields I have observed.

This year appears to be an early-season S deficiency year. Sulfur is a critical micronutrient for crop production because of its primary role in plant and grain protein formation. Sulfur must be mineralized (chemical and biological oxidation of organic and elemental forms S0 to the SO4-2 form) in order to become available for plant uptake. The rate of S mineralization can be significantly impacted by the soil moisture content, and the root-zone oxygen concentration and quantity of SO4-2   sulfur in the root zone can also be influenced by downward water movement (or leaching) during significant rainfall events.   

The heavy rainfall we’ve experienced throughout much of the state during planting season resulted in waterlogged soils with very low oxygen concentration and leaching in coarser-textured soils.    Initial symptoms observed this year were interveinal-chlorosis (alternating green and yellow stripes) in new leaves unfurling from the whorl. As S deficiency has progressed, corn and soybean plants have become stunted and are experiencing an overall lime-green to yellow appearance, especially at the top of the crop canopy.

Crop S nutrition is best obtained by applying S as part of your overall soil fertility program and by adopting management practices that encourage conservation and buildup of topsoil and organic matter.  Often, S is applied in the 90 percent S elemental form (the yellow product) when phosphorus (P) and potassium (K) are applied. This practice can help build overall S levels in the soil and increase the potential amount of S that can be oxidized into SO4-2   sulfur and made plant available. However, this process takes time and is mediated by specific microbes in the soil. Because of the time required to convert the applied elemental S to the plant-available form, I recommend applying the “yellow” elemental S fertilizer in fall applications, not spring. I often recommend spring applications of 100 lb. of ammonium sulfate (21-0-0-24) ahead of corn and soybean planting, especially in high-yielding environments.   Ammonium sulfate is a fantastic product that contains both readily plant-available nitrogen (NH41) and sulfur (SO4-2). Applications of ammonium sulfate ahead of corn and soybean planting can benefit crops by:

  1. Providing a nicely balanced N:S starter in the shallow root zone for plants between emergence and the V5 growth stage.
  2. Accelerating the corn root growth to anhydrous ammonia application zones so that corn plants can begin to maximize root interception and uptake of N more quickly. This leads to more rapid crop development and progression toward pollination. This is important in Missouri as we are often trying to grow corn before the soil moisture is depleted and air temperatures increases significantly.
  3. Providing a small amount of N and S to young soybean plants during a time when soil conditions may not allow for normal development and function of nitrogen-fixing nodules.
  4. Helping improve the N to S supply ratio for plant and grain protein formation.

This year, we have an interesting Practical Farm Research (PFR)® Partners study in the Carrolton, Missouri River bottom where Casner Farms and Beck’s are evaluating to see if corn will respond to pre-plant, strip-till applied ammonium sulfate. Early observations show that this practice is resulting in significant visual differences in corn already. We are headed out there today (Monday, July 12) to apply the sidedress N component of the study. We will keep you posted on the visual and yield observations as this study progresses.

Remember, it’s more challenging to remediate S deficiency in fields than to simply provide enough S to begin with. But even when you do things right, conditions can move S below the root zone and reduce S mineralization and oxidation rates.

In S-deficient fields right now, I recommend to:

  1. Reassess how much S was applied ahead of this year’s crop and whether it was in the elemental S0 form or SO4-2  (yellow 90 percent form or ammonium sulfate form).
  2. Assess the organic matter content and status of your field.
  3. Hold off if you have good organic matter soils (2.5 percent or greater) and had applied ammonium-sulfate. The S deficiency in your fields is likely temporary and will self-correct with aeration and increased root growth and exploration of the soil volume.
  4. Apply more S if you have lower organic-matter soils (less than 2.5 percent) and/or applied elemental sulfur or no sulfur. In this instance, I would recommend an application of an ammonium-sulfate based foliar product like one to two qt. of Versa MAX™ AC or 16 to 24 oz. of PercPlus™ as soon as possible or in your next post-emergent herbicide application pass.  Both of these products should be added to the tank water first and mixed well before adding any herbicide or insecticide products. 


If you have any questions, please contact myself or your local Beck’s representative.









Practical Farm Research (PFR)® is a registered trademark of Beck’s Superior Hybrids, Inc. Versa Max™ AC is a trademark of Midtech R&D, Inc. PercPlus™ is a trademark of DeltAg Formulations.

Comments (1)Number of views (18619)

Author: David Hughes

Categories: Agronomy, Missouri, Field News


David Hughes

David Hughes

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1 comments on article "Field News"

Lincoln Hughes

8/1/2017 10:23 PM

We plant all Monsanto products. We really like drought guard hybrids what does becks have that will compete or beat.. Been playing with 15 inch corn you playing with any of that. And I your corn book it doesn't list flex on ear

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