Earlier planting dates in cooler soils, increased nutrient removal by higher yielding cultivars, and reductions in atmospheric sulfur (S) deposition suggest that S application may require reassessment in Michigan for optimal corn (Zea mays L.) and soybean (Glycine max L.) growth. Field experiments were conducted on corn to examine the effect of a range of S rates with increasing nitrogen (N) rates on grain yield. The results indicated S availability may be sufficient when optimal N rates are applied promoting sufficient root growth to exploit the soil profile and acquire sufficient S quantities for optimal plant growth, however, yield responses to S may vary with environmental conditions (i.e., soil organic matter, soil texture, soil phosphorus (P) levels, and crop rotation). Residual soil S, mineralization of soil organic matter, S deposition from rainfall, and possible sub-soil S accumulation should all be considered for potential S contributions to determine when S application is justified. A soybean field trial investigated S placement at 25 lbs S/acre while evaluating the presence of a starter fertilizer (20 lbs N and 50 lbs P2O5/acre) in a 2 × 2 inch band. Although starter fertilizer had no significant effect on soybean grain yield or quality, in both study years soybean canopy density and greenness were greater with starter fertilizer application prior to V4. No significant effect on grain yield from S placement occurred in either study year suggesting sufficient S was cycling in the soil profile for optimal soybean growth to occur. Evaluating residual soil S and organic matter levels at the time of planting may be necessary to determine if S application is justified for optimal corn and soybean growth.
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