Sulfur Fertilizer Effects on Dry Matter Production and Nutrient Uptake of Juvenile Corn.

The importance of adequate sulfur (S) for corn (Zea mays L.) production has been recognized for many years, and recently, positive yield responses to S fertilizer have been documented. The responses, however, have not been consistent. The objective for this study was to determine the response of juvenile corn to S applied as a granular S-enhanced mono-ammonium phosphate material [MAPS (13-33-0-15S)], granular ammonium sulfate [AMS (21-0-0-24S)], and liquid ammonium thiosulfate [ATS (12-0-0-26S)]. Soils were collected from eroded hillslopes in central Iowa (Clarion loam; fine-loamy, mixed, mesic Typic Haplaquolls), northeastern Iowa (Fayette silt loam; fine-silty, mixed, superactive, mesic Typic Hapludalfs), and southeastern Iowa (Muscatine silt loam; fine-silty, mixed, superactive, mesic Aquic Hapludolls). Fertilizer materials were applied at 0, 22, 34, and 45 kg S ha^-1. Pre-germinated corn (Pioneer 36N71) seedlings were planted in pots containing three kg of treated soil and placed in a controlled-climate chamber. After 21 days, pots were harvested, and total dry matter production (shoots and roots) and nutrient (S, N, P, K) uptake from each treatment were measured. Application of 34 kg S ha^-1 as MAPS significantly (P≤0.05) increased mean shoot dry weight. A similar but non-significant trend was found for AMS and ATS. Mean root dry weight was not affected by S rate or source. Whole-plant S concentrations were generally higher than the control for all S sources. For these juvenile plants, the agronomic efficiency of S (DM yield per unit applied) was greatest for AMS. Because surface soil on hill slopes often is eroded, common fertilizer materials contain less S as an impurity, and atmospheric deposition of S has decreased in the upper Midwest, the results of this study suggest that early season growth of corn in many areas of Iowa may benefit from S fertilizer application.