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Central Illinois | This information is from an Iowa State University study from 2007 and 2008:
Studies were conducted in 2007 and 2008 at forty-five sites to determine corn response to S rate of application. The sites were selected to represent major soils and cropping systems, and were chosen to represent a range in potential S response. Most sites were on producer fields.
Corn grain yield was increased (statistically significant) with S fertilizer application at 17 of the 20 sites in 2007 and 11 of the 25 sites in 2008 (Figs. 1 and 2) and leaf S concentration was increased at 16 sites each year (data not shown). Across all sites, the average yield increase was 13 bu/acre. When grouped by soil texture for responsive sites, the yield increase was 15 bu/acre for the fine-textured soils (loam, silt loam, silty clay loam, and clay loam) and 28 bu/acre for the coarse-textured soils (fine sandy loam, loamy fine sand, and sandy loam). Grain yields increased with S application at 21 of 34 (62%) fine-textured soil sites and 7 of 11 (64%) coarse-textured soil sites. These are frequent and large yield increases to S fertilization.
While nutrient use efficiency is important and interesting, for producers the important question is what is the economic optimum application rate? When analyzed for the responsive sites, the maximum response rate for the 21 fine-textured soil sites was 17 lb S/acre, with an economic optimum rate at 16 lb S/acre (Fig. 3). For the 7 coarse-textured soil sites, the maximum response rate was 25 lb S/acre, with an economic optimum rate at 23 lb S/acre (Fig. 3). The economic optimum S rate is near the maximum response because the fertilizer cost (rate times price) is low compared to the yield return (yield increase times corn price).
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Ammonium Sulfate question
