Corn Response to Nitrogen at Multiple Sulfur Rates

Abstract

Early planting into cooler soils, increased nutrient removal by higher yielding hybrids, and reduced atmospheric S depositions suggest reassessing S application strategies for corn ( Zea mays L.) in Michigan. In 2012 and 2013, field studies were initiated to evaluate corn response to S and N applications by measuring S and N plant concentrations, uptake, grain yield, and agronomic efficiency (AE). The study was arranged as a split‐plot randomized complete block with four replications. Main plots consisted of three S rates (0, 23, and 45 kg S ha −1 ) while subplots consisted of six N rates (0, 56, 112, 169, 225, and 281 kg N ha −1 ). Corn tissue V6 S concentrations were in the sufficiency range for optimal corn growth without S in 1 of 2 yr. Without N fertilizer, significant yield differences were observed among the 0, 23, and 45 kg S rates in 2012 (6.7, 7.7, and 9.5 Mg ha −1 , respectively) and 2013 (3.2, 5.7, and 3.5 Mg ha −1 , respectively). In 2013, significant yield increases to S applications occurred only at ≤56 kg N ha −1 . Data suggest fine‐textured soils with organic matter ≥ 28 g kg −1 and residual S ≥ 6–8 mg kg −1 are sufficient for maximum corn yield without S when N application rates exceed 56 kg N ha −1 . Choosing optimal corn N application rates may satisfy physiological S requirements under these field conditions indicating N/S ratio may not have been sufficient at N rates ≤ 56 kg N ha −1 .