Corn Response to Sulfur Application in Coastal Plain Soils

Sulfur (S) fertilization is expected to increase corn (Zea mays L.) yields in coarse-textured, well-drained, and low organic matter Coastal Plain soils. This increase is expected because of the reduced quantities of S applied to agricultural lands in the form of by-products from fertilizers applied to satisfy other nutrient requirements, increased removal of S from soil with increased crop yields, and increased emphasis on reducing atmospheric pollutants (thus decreasing S additions from atmospheric sources). This study was conducted to determine if corn yields could be increased by S additions to Coastal Plain soils and to determine if extractable soil S or tissue analyses could be employed to predict this response. Ten S fertilization experiments were conducted over a wide range of soils during 1978,1979, and 1980. Results showed that increased corn yields can be expected with S application on soils that are moderately well to well-drained, low in organic matter, and belong to the fine loamy or coarser textured family of soils, and have acid monocalcium phosphate extractable soil SO₄-S concentrations ≤ 2.3 mg kg⁻¹ in the surface horizon. When extractable soil S present in the Ap horizon was related to actual yield increases (∆y max) with a refitted Mitscherlich equation, a significant relationship was evident and 62% of the observed variability in relative yield could be explained. Fertilizer applications ranging from 18 to 28 kg S ha⁻¹ were required to achieve 90% of maximum yield. The requirements appeared to be dependent on the method of application (broadcast preplant or split between broadcast and sidedress). When the relationship between total S and N:S ratio in the leaf below and opposite the ear leaf at silking and ∆y max was examined, 67 and 82% of the observed variation in ∆y max could be explained by a refitted Mitscherlich and a linear equation, respectively. From these equations it was estimated that the critical concentration for total S and N:S ratio would be 1.7 g kg⁻¹ and 16, respectively. These data indicate that extractable soil S or tissue analyses could be used to identify fields that might be S deficient.