No. 23 Article 6/October 8, 2010

Do You Need Sulfur for Corn?

This question of whether sulfur is needed for corn piqued my interest, and I am conducting research to try to answer it. We started a study in 2009 to evaluate the response of corn to sulfur. While some locations showed no response, others did. The responsive locations showed yield increases ranging from a few bushels to more than 50 bushels per acre compared to the untreated check. I don't have much yield data from this year yet, but visually some trials were showing response to sulfur during the summer.

Sulfur is a very important nutrient for corn production. Historically, routine sulfur application for corn has not been recommended in Illinois because earlier research showed no response to sulfur and because soil supply, manure applications, and/or atmospheric deposition were sufficient to supply sulfur needs for this crop. However, soil sulfur levels or supply may have diminished over time as a result of several factors.

Strict air pollution standards have cleaned the air of gaseous sulfur compounds, resulting in less sulfur atmospheric deposition. In general, many agronomic inputs, including fertilizers, insecticides, and fungicides, are "cleaner," containing less incidental sulfur. Also, the reduction in livestock operations across the state is leading to application of less manure, further reducing the amount of sulfur applied or deposited on the soil.

At the same time that less incidental sulfur is being applied or deposited, increasing crop yields mean more sulfur is being removed. All of these factors, and the fact that we saw some response during last year's sulfur trials, would indicate a need to continue investigating sulfur fertilization for corn in Illinois.

The fact that some but not all fields responded to sulfur application in last year's trials is a clear indication that some locations or soil conditions may be more responsive than others. This study will produce valuable information regarding the frequency of sulfur deficiency that we can expect and, most important, which Illinois regions or conditions are most likely to experience deficiencies.

We need the help of volunteers to increase the usefulness of this project to Illinois farmers. I am looking for producers throughout Illinois who are willing to participate in on-farm research to measure corn response to sulfur fertilization. The better coverage of the state we can achieve, the greater will be our ability to predict where sulfur applications will most be needed.

Express your interest. If you are interested in participating (even if you are not sure whether your particular field or equipment would fit the conditions for this study), or if you have questions about how to find sulfur fertilizer or have the fertilizer applied, please contact me (fernande@illinois.edu; 217-333-4426; Department of Crop Sciences, N-315 Turner Hall MC-046, 1102 S. Goodwin Ave., Urbana, IL 61801).

Soil conditions. We want to characterize sulfur response across the state, so we will consider all soil types. However, we are especially interested in light-colored soils (less than 2% organic matter, coarse texture, or both) and soils with an eroded phase. The only fields we will not consider are those that have received manure or sulfur application in the last five years.

Logistics. Volunteers conducting these trials will follow a simple design, applying 0 and 30 lb of sulfur per acre as a broadcast application in a uniform portion of the field. From three replications to eight are needed for each field. Figure 1 shows a layout of the treatments randomly assigned within each replication for an eight-replication study. It will be important to geo-reference each strip or clearly mark it with different-colored flags or markers in the center. Strips can be anywhere from 8 to 16 rows wide by 300 to 1,000 feet long. What is important is that the size of the strip allow accurate application of the rate and accurate measurement of yield. Also, it is preferable that the strip be wider than the harvest strip, but if the combine is at least 12 to 16 rows wide, it is possible to harvest the strip without having border rows.


Figure 1. Layout of the treatments randomly assigned within each replication for an eight-replication study.

Sulfur sources. While there are a few sulfur sources we prefer, we can accommodate others. We would prefer the use of ammonium sulfate (NH4)2SO4 (21-0-0-24), MicroEssentials sulfur (ME S) ME S15 (13-33-0-15), or elemental sulfur (0-0-0-90). If your sulfur source contains other accompanying nutrients, you will need to apply the corresponding rates of those nutrients to other treatment strips to avoid a differential response. If you use ammonium sulfate, you would need to apply 26 lb N/acre to the other strips; if you use ME S15 you would need to apply 145 lb DAP (18-46-0)/acre. (For more details see the section on "Applying the treatments.")

Time of application. This fall soils are dry, and harvest for most people is moving forward in a timely fashion. Applying treatments this fall would definitely be an option. Our preferred application time is the spring (preplant), but we understand that fall might be the only choice available to some of you. If you prefer to use ammonium sulfate this fall, make sure to follow guidelines for fall nitrogen applications. Whether fall or spring works best for you to apply sulfur, what is most important for us is having as many locations as possible throughout the state to be able to characterize the potential for corn response to sulfur in Illinois.

Measurements for data collection. The only data volunteers will have to provide is the yield for each strip. This information can be collected by yield monitor or from a weigh wagon. Volunteers will not be required to take plant or soil samples, but they need to agree for the researcher to visit the strips two or three times during the growing season.

Applying the treatments. There are three sulfur sources to choose from:

For strips with 30 lb sulfur/acre: Apply 125 lb ammonium sulfate/acre.

For the strip with 0 lb sulfur/acre: Apply 26 lb nitrogen/acre. This application is made to balance the nitrogen that was applied along with the sulfur in the sulfur strip. Those 26 lb of nitrogen/acre can be applied as either 57 lb urea/acre, 94 lb UAN (28%)/acre (8.7 gal/acre), or 82 lb UAN (32%)/acre (7.4 gal/acre). Do not use anhydrous ammonia because it would be difficult to apply only 32 lb of product/acre.

For strips with 30 lb sulfur/acre: Apply 200 lb MES-15/acre.

For the strip with 0 lb sulfur/acre: Apply 145 lb DAP (18-46-0)/acre. This application is made to balance the nitrogen and phosphorus that was applied along with the sulfur in the sulfur strip.

I would use elemental sulfur only as a last resort, because often all of it does not become available in the year of application.

For the strip with 30 lb sulfur/acre: Apply 33 lb elemental S/acre.

For the strip with 0 lb sulfur/acre: There is no need to apply any product because the sulfur source is not accompanied by any other nutrient.

Additional N, P, K, or other inputs. If the field needs additional nutrients or other inputs (insecticide, herbicide, etc.) to optimize production, make sure those inputs are applied at the same rate across the entire study site.--Fabián G. Fernández

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