No. 1 Article 10/March 26, 2010

Do I Need to Apply Sulfur to My Corn Crop?

This question is what got me interested in doing sulfur (S) research for corn, and we started a study in 2009. While some locations showed no response to sulfur applied to corn, others did. The responsive locations showed yield increases ranging from a few bushels to more than 50 per acre compared to the untreated check.

Sulfur is a very important nutrient for corn production. Historically, routine application has not been recommended for corn 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. Strict pollution standards have cleaned the air of gaseous sulfur compounds, with less sulfur atmospheric deposition the result. In general, many agronomic inputs, including fertilizers, insecticides, and fungicides, are "cleaner," containing less incidental sulfur. Also, fewer livestock operations across the state means less application of manure as fertilizer, which further reduces the amount of sulfur being applied.

At the same time that less incidental sulfur is being applied or deposited, there is greater removal of sulfur by increasing crop yields. All of these factors, and the fact that we saw some response during last year's sulfur trials, would indicate that we should continue investigating sulfur fertilization for corn in Illinois.

The fact that some fields responded to the application of sulfur and others did not in our 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 importantly, what regions or conditions are most likely to experience deficiencies.

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

Soil conditions. We are interested in light-colored soils (less than 2% organic matter, coarse texture, or both) and soils with an eroded phase. However, we would like to characterize sulfur response across Illinois, so we will also consider other more "traditional" soils. Fields that have received manure or sulfur applications within the last five years will not be considered.

Equipment. Volunteers will follow a simple design applying 0 and 30 lb S/acre as a broadcast application in a uniform portion of the field. A minimum of three replications or as many as 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 georeference or clearly mark each strip 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, and if possible that it be wider than the harvest strip. However, 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 treatments randomly assigned within each replication for an eight-replication study.

Sulfur sources and application timing. Sulfur sources will be limited to ammonium sulfate (NH4)2SO4 (21-0-0-24); MicroEssentials sulfur (ME S) MES15 (13-33-0-15); and elemental sulfur (0-0-0-90). (However, I would use elemental sulfur only as a last resort because often it does not become all available in the year of application.) If the sulfur source contains other accompanying nutrients, the corresponding rates of those nutrients will need to be applied to other treatment strips to avoid a differential response to nutrients other than sulfur. If you use ammonium sulfate you will need to apply 26 lb N/acre to the other strips; if you use ME S15 you will need to apply 145 lb DAP (18-46-0)/acre. (More details are provided below.)

The preferred application time is spring, but if the only time available is fall, we can accommodate that. What is most important to us is to include as many locations as possible throughout the state.

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 must be willing for the researcher to visit the strips several times during the growing season.

Apply treatments. Instructions for the three sulfur sources follow.

For strips with 30 lb S/acre, apply 125 lb ammonium sulfate/acre. For the strip with 0 lb S/acre, apply 26 lb N/acre. This application is to balance the N applied along with the S in the sulfur strip. Those 26 lb of N/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 per acre.

For the strips with 30 lb S/acre, apply 200 lb MES15/acre. For the strip with 0 lb S/acre, apply 145 lb DAP (18-46-0)/acre. This application is to balance the N and P applied along with the S in the sulfur strip.

For the strip with 30 lb S/acre, apply 33 lb elemental S/acre. For the strip with 0 lb S/acre, there is no need to apply any product because the S source is not accompanied by any other nutrient.

Additional N, P, or K or any other input. 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.

If you are interested in participating--even if you are unsure whether your field or equipment fits the conditions for the 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).--Fabián G. Fernández

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