Project Details:

Sulfur Synergies in Soybean Management (Year 2)

Parent Project: Sulfur Synergies in Soybean Management
Checkoff Organization:Indiana Soybean Alliance
Categories:Crop management systems, Soybean utilization, Environmental stress
Organization Project Code:
Project Year:2019
Lead Principal Investigator:Shaun Casteel (Purdue University)
Co-Principal Investigators:
Keywords: crop management

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

Sulfur (S) deposition from the atmosphere has been on the decline over the last few decades due to the improvements in air quality, especially due to the Clean Air Act amendment in 1990. Approximately 10 to 18 lb of S/acre was deposited from the atmosphere to the soils of Indiana in 2001; whereas, only 4 to 8 lb of S/acre were deposited in 2015. Sulfur is a macro-nutrient that is needed in large quantities for all crops including soybean. In fact, S is needed as a co-factor for
proper nodulation and fixation by Bradyrhizobium japonicum for soybean. Soybean takes up 0.35 lb of S per bushel, so 50 to 75-bu soybeans would need 17.5 to 26 lb S/ac. A little over half of this S is removed in the grain (largely in amino acids of the protein), thus 9 to 13.5 lb S/ac is removed from the field in the grain (50 to 75 bu). Organic matter in the soil can help make up the difference in crop need and deposition from the atmosphere, but evidence is mounting that more S is needed in some fields for soybean.

Our research aims to determine the best options (e.g., fertilizer sources to be broadcast applied prior to planting/emergence, foliar sprays during the growing season) to manage S for soybean and determine opportunities for synergies in management to optimize yield and quality (i.e., protein). First year results of this project has documented 10+ bu responses to ammonium sulfate (AMS, 21-0-0-24S), MES10 (12-40-0-10S), and pelletized Gypsum (21% Ca, 17% S)
followed by ~6 bu responses to the other sulfur sources at LaCrosse in 2018. At the same location, optimal foliar S application rate was ~4 lb S/ac regardless of growth stage applied (V4 or R3) with over 8 bu yield improvement. Synergies in management seem to align more with combined applications of AMS prior to emergence and foliar protection at R4 than seed-applied inoculant and AMS application prior to emergence at Wanatah and West Lafayette in 2018.

These studies should be conducted in 2019 to confirm repeatability and fine-tune recommendations.

Project Objectives

We have documented substantial yield responses of soybean to sulfur (S) applications over the last few years (6 to 13 bu/ac). Our research aims to find synergies in soybean management to optimize S applications (where needed) for yield and quality responses.

Our objectives are to:
1. Determine management practices to alleviate S deficiency of soybean in the most responsive and cost-effective manner,
2. Characterize the physiological changes that have improved soybean grain yield and quality in response to S applications (e.g., nodule production, fixation, leaf production, branching, pod development and retention, seeds)

Project Deliverables

Preliminary results from the 2016 and 2017 seasons have already been shared across Indiana. The results from 2018 will continued to be presented at Extension winter workshops, meetings, and conferences of producers, Extension educators, and crop professionals across Indiana.

Conclusions from the experiments in 2018 and 2019 will be shared with Extension audiences in presentations, newsletter articles, and Web sites. We will also share these findings at the American Society of Agronomy meetings.

Progress of Work

Final Project Results

Benefit to Soybean Farmers

We aim to determine the most effective method of correcting S deficiencies of soybean both agronomically and economically. Additionally, we will start to tease out the field situations where is S is warranted. Our preliminary studies have indicated the protein concentration is also improved with our S applications. Thus, we could also provide an underpinning for management strategies to maintain yield and improve quality.

Performance Metrics

Project Years