Field studies were conducted over a three-year period at a total of 82 site-years to evaluate the sulfur (S) status of representative Illinois soils. In addition, greenhouse studies were conducted using soils from two of the three years of field experiments. The sites selected were either low in organic matter, sandy in texture and/or in areas 

where apparent S deficiency had been reported. At each location, gypsum was applied at a rate to supply 50 lb S/ac prior to the final tillage operation before planting. Whole plant samples were collected at the sixth-leaf stage of growth and ear leaf samples were collected at silking for S analysis. Soil was collected from each location in the second and third year of the study for use in the greenhouse study. Corn yield was measured in both the field and  greenhouse  studies.

Significant yield response to applied S was observed at five of the 81 locations studied - with an average increase of ll.2 bu/ac. For the 76 nonresponding sites, where there were no significant responses, yields on the S treated plots were an average of 0.5 bu/ac greater than the control treatments indicating that S had little influence on grain yield at these sites. In the greenhouse, plants responded to the application of S during the second crop ping period on 60% of the soils evaluated.

Under field conditions, plants grown on the untreated plots had adequate S concentration in the plant tissue at all but two locations. However, in the greenhouse, the concentration of S in plants grown on the untreated soil was below the critical level on 41% and 91% of the soils at first and second harvest, respectively.

Sulfur in precipitation collected during the growing season ranged from 3.6 to 18.9 lb S/ac. The S soil test reliably predicted S deficiency at four of the five respond­ing locations. However, it did not reliably predict those sites which did not respond to S as 14 of the nonresponding sites had levels below those normally considered to be deficient.

The differential response to S observed between the field and greenhouse studies implies that the soils have low ability to supply S and/or that the atmospheric contribution of S in the field is a major contributor to the S nutrition of field grown plants. If the latter is correct, then continued reduction in atmospheric S supply combined with higher crop yields will likely result in more frequent occurrences of S deficiency in field crops grown on Illinois soils.