Maize response to sulfur fertilizer in three Iowa soils

Authors: Kovar, John

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2020
Publication Date: 1/11/2021
Citation: Kovar, J.L. 2021. Maize response to sulfur fertilizer in three Iowa soils. Communications in Soil Science and Plant Analysis. 52(8):905-915. https://doi.org/10.1080/00103624.2020.1869773.
DOI: https://doi.org/10.1080/00103624.2020.1869773

Interpretive Summary: Sulfur (S) is an essential plant nutrient that must be available to corn roots in order to achieve optimum growth of the plant. Our understanding of the effects of S fertilizer sources and amounts to apply to soils in Iowa is limited. With a controlled climate study, we evaluated the performance of three S fertilizers as S sources for corn grown in three diverse Iowa soils. We found that plant-available S generally increased when more S fertilizer was applied to the three soils, but the type of S fertilizer did not matter. The type of soil and the amount of S fertilizer had the greatest effect on growth of the young corn plants, as well as amount of S captured by the plant roots. Fertilizer S increased corn growth when ammonium sulfate fertilizer was applied to Clarion loam soil and when S fertilizer from any of the three sources was applied to Muscatine silt loam soil. Sulfur fertilizer had no effect on corn growth in Fayette silt loam soil. For several reasons including erosion of high-fertility hill slope soils, fewer S impurities in fertilizers, and decreased atmospheric deposition of S throughout the upper Midwest, our results suggest that S may become a more widespread limiting nutrient for corn production. The results of this research will benefit both commercial growers and the fertilizer industry by providing nutrient management guidelines that maximize crop utilization and yields.

Technical Abstract: The importance of adequate sulfur (S) for maize (Zea mays L.) production has been recognized for many years, and recently, positive yield responses to S fertilizer have been documented in Iowa. The responses, however, have not been consistent. The objective for this study was to determine the response of juvenile maize to S applied as granular ammonium sulfate (AMS; 21-0-0-24S), liquid ammonium thiosulfate (ATS; 12-0-0-26S), and granular S-enhanced mono-ammonium phosphate (MAPS; 13-33-0-15S). Soils were collected from eroded hillslopes in central Iowa (Clarion loam; Typic Haplaquolls), northeastern Iowa (Fayette silt loam; Typic Hapludalfs), and southeastern Iowa (Muscatine silt loam; Aquic Hapludolls). Fertilizer materials were applied at 0, 22, 34, and 45 kg S ha-1. Pre-germinated maize (Pioneer 36N71) seedlings were planted in pots 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. Plant-available S generally increased with increasing S application rate in the three soils, but S source had no effect. Soil type and S fertilizer rate had the greatest effect on maize growth, as well as S nutrition of the plants. Fertilizer S application increased maize shoot DM when AMS was applied to the Clarion loam and when S fertilizer from any source was applied to the Muscatine silt loam. Sulfur fertilizer application had no effect on maize DM accumulation in Fayette silt loam. Shoot DM ranged from 3.06 g plant-1 (with 22 kg S ha-1 as AMS in Fayette silt loam) to 6.2 g plant-1 (with 45 kg S ha-1 as AMS in Clarion loam). Mean root DM within each soil type 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 the Muscatine soil, and was not related to S source or application rate. The results of this study suggest that early season growth of maize in many areas of Iowa may benefit from S fertilizer application, but the response may be site-specific.