Corn Yield Response to SuperCal SO4
Location: Northern/NE Iowa
Date: 2006 - 2008
Treatments: Initial: 40 lbs S/acre (SuperCal SO4 @ 235 lbs/A)
Follow-up: 10, 20, 40 lbs S/acre (SuperCal SO4 @ 60, 117, 235 lbs/A)
Initial Trial (Sawyer et al., 2011)
Trials were initiated in 2006 (Sawyer et al., 2011) to evaluate yield response in corn, where five out of six sites showed a yield increase that averaged 38 bu/A from SuperCal SO4 applied at 235 lbs/A. Sites were chosen based on visibly sulfur deficient corn and applications were top-dressed. Corn plants showed a quick response with rainfall after SuperCal SO4 application.
Follow-Up Trials (Sawyer et al., 2011)
Due to the response from the initial trials, 45 trial sites in north-central to northeast Iowa were established in 2007 and 2008 to determine corn response to S rate. These sites were selected to represent major soils, cropping systems, and a range in potential S response. SuperCal SO4 was surface applied without incorporation after planting at 60, 117, and 235 lbs/A. Yield was increased with SuperCal SO4 applications at 17 of 20 sites in 2007 and 11 of 25 sites in 2008. Across all sites, yield increase averaged 13 bu/A. When analyzed by responsive sites, the maximum SuperCal SO4 response rate for fine-textured soils was 100 lbs/A, while coarse-textured soils showed maximum yield with 150 lbs/A.
One very interesting result from this study was showing that SO4-S soil testing does not always determine if a yield response will result from S application. Concentrations above 10 ppm are generally considered sufficient, but some of the sites in this trial showed yield response even when the soil test for SO4-S was above 10 ppm. These results highlight the complex influence of many factors (environment, soil, and crops) that result in sulfur availability over a growing season. Visual observation of sulfur deficiency can lead to correct determination of S response.
Overall, this research indicates a need for a paradigm shift in S fertilization, which has historically been an overlooked nutrient in corn. Make the smart choice for your corn and apply SuperCal SO4 to meet your crop’s sulfur needs!