Status of Sulfur in Pennsylvania Corn Production.

Historically sulfur (S) has not been a fertility concern in Pennsylvania crop production because of significant S deposition in acid rain.  A statewide survey of S in crops conducted in 2001 found no evidence of S deficiency.  However, there has been a dramatic reduction in S deposition, resulting in a declining trend in soil test S levels, and increasing reports of suspected S deficiency in crops in PA.  In 2014 and 2015 a new survey of corn S status was conducted.  Extension educators across the state collected plant tissue and soil samples from 78 representative corn fields.  Management data was also collected for each field sampled.  Median Mehlich 3 soil test S was 18 ppm S, which is very similar to the median S (15 ppm S) for all farmer soil samples submitted to the Ag Analytical Services Lab at Penn State.  Median corn earleaf S from the survey was 0.18%.  In the survey, 75% of the samples were below the optimum range of 0.2 – 0.5% used in PA.  There was a very weak relationship between earleaf S and Mehlich 3 soil test S (r²= 0.12).  Approximately one-half of the sites sampled had a history of frequent manure and/or S fertilizer application application.  There was a slight trend toward higher earleaf and soil S levels where there was a history of manure or S application.  Starting in 2015, S response experiments were conducted at 7 on-farm locations across the state.  There was a significant yield response to S (p=0.1) at 4 of 7 locations.  Average yield response to S was 13 bu/A.  Soil test and plant S were variable, but roughly followed the trend in yield response.  Survey and S response experiments are continuing in 2016.