Response of Irrigated Corn to Sulfur Fertilization in the Atlantic Coastal Plain

Accurate prediction of yield response by corn ( Zea Mays L.) to S fertilization on the coarse‐textured soils of the Atlantic Coastal Plain requires information on availability and persistence of subsoil SO 4 ‐S, potentially mineralizable soil S, and S added in irrigation and precipitation. A 3‐yr study was conducted with irrigated corn on four soils possessing characteristics commonly associated with S deficiency. A factorial combination of S application rate (0, 33, 67, 101 kg ha −1 ) and method (single broadcast at planting, split) was used. Grain yield, and S concentrations and N/S ratios of early whole plants (EWP) and ear leaves (EL) were determined. Extractable SO 4 ‐S (0–100 cm) levels and inputs of S from irrigation and precipitation were measured in each year; mineralizable S in Ap horizons of all soils was determined by two incubation methods (leached and nonleached). Although application of S generally increased plant S concentrations, significant yield increases occurred in only three of the 12 site‐year combinations. Critical values for S and N/S, based on combined data from responsive sites, were 2.1 and 1.6 g S kg −1 and 18.7 and 20.3, for EWP and EL, respectively. Lack of yield response was attributed to subsoil SO 4 ‐S, (average, 0–100 cm = 170 kg S ha −1 , mineralizable S (average = 80 kg ha −1 , leached method) and S contained in irrigation or precipitation (annual average = 7.5 kg ha −1 ). Yield increases obtained at the most responsive site may have been caused by increased immobilization of S, due to no‐tillage management, the presence of a physical barrier to root penetration at 40 to 60 cm, or subsoil Al. Successful prediction of corn response to S fertilization in Coastal Plain soils will require a comprehensive program that combines subsoil sampling and selective plant analysis, concentrated on sites identified as potentially responsive based on soil properties.