Wednesday, November 15, 2006

Sulfur and Nitrogen Starter Fertilizer for Corn in Northern Climates.

B.E. Daley, R.J. Gehl, K.D. Thelen, and D.D. Warncke. Michigan State Univ, 566 Pssb, East Lansing, MI 48824

A combination of cool, wet weather in early spring and planting in reduced-tillage or no-till fields reduces the amount of sulfur and nitrogen that is released in the soil by decomposition and mineralization of organic matter, particularly in northern regions of the U.S.  Recent changes to sulfur emission regulations have decreased the amounts of sulfur that is deposited to the soil through atmospheric channels.  Field studies were conducted in 2005 at six corn (Zea mays L.) sites in Michigan to evaluate the effects of sulfur starter fertilizer on nutrient uptake, plant growth, and grain yield.  Four sites were on-farm strip trials with treatments of ammonium sulfate (21-0-0-24S) band-applied at planting at rates of 0, 5.6, 11.2, and 22.4 kg S ha-1.  Two other sites on university research farms included additional starter fertilizer treatments of 28 kg N ha-1, 28 kg N ha-1 + 28 kg P2O5 ha-1,  28 kg N ha-1 + 28 kg P2O5 ha-1 + 11.2 kg S ha-1, and 11.2 kg S ha-1 as gypsum (16% S).  Grain yield responded positively to the 22.4 kg S ha-1 application at two of the six sites in the study, with an average of 16.4 Mg ha-1 increase in grain yield over the control (0 kg S ha-1).  One site showed a negative response (yield) to the 22.4 kg S ha-1 treatment, likely due to salt toxicity stemming from fertilizer being placed directly below the seed.  No yield differences were observed among any of the other starter treatments at any of the locations.  Responses observed in plant tissue S content and grain yield at the strip trial sites may be attributed to nitrogen rather than sulfur.  When sulfur was applied as gypsum, there was no yield difference compared with the control plots.