This research will evaluate various biologicals that are marketed to soybean to enhance availability, supply, and/or uptake of nutrient (e.g., N, P, S); thereby, reducing nutrient inputs. These enhancements in nutrient management imply an environmental benefit as well as yield and profit. Other biologicals claim to promote soybean growth and development, which, would impact nutrient acquisition and yield.

To this end, we will determine the best biological options based on category and application method. Biologicals include bacteria, fungi, enzymes, amino acids, marine extracts and more. Several examples include non-rhizobial bacteria that fix atmospheric N, bacteria that solubilize P from soil minerals, phosphatase enzyme that release P bound to organic matter, and marine extracts that stimulate other microbes and roots for nutrient uptake and water stress. The first study, Nutrient Influencing Biologicals, will evaluate representative products within these categories and apply them in the recommended methods (i.e., seed treatment, in-furrow, broadcasted to soil, foliar application). Farmers will provide direction in the selection of these biologicals through a winter survey. The final 16 treatments will be evaluated on three soil types prairie (West Lafayette), loam (Wanatah), and sand (Wanatah). These soil types will provide a cross section of nutrient supplying capacity, organic matter, water holding capacity, and yield potential. The second study, Non-Rhizobial N Supplier x Fertility, will be focused evaluation of the interaction of fertility (i.e., N and S) and the potential supply of N from non-rhizobial sources. This research also aligns well with ISA Discovery Goal of “Profits by Prescription.”

Our research aims to develop management systems to improve nutrient use, yield, and quality. Our objectives are to:
1. Determine the best biologicals and methods of application to improve nutrient use (i.e., nitrogen, sulfur), yield, and quality
2. Determine management and/or field conditions that impact soybean response to biologicals that have nutrient availability/efficiency claims
3. Improve nitrogen supply and explore synergies within newer fertility management (i.e., non-rhizobial N suppliers and S fertility) to improve yield and quality.

A natural outcome of these objectives will be the selection of biologicals and application methods to be evaluated at field-scale and with collaborators to build the database for responsiveness and recommendations. The details of leaf nutrition and yield will be the avenue to determine treatment effects as well as direct further exploration and explanation. All trials will be subjected to statistical analyses to provide conclusions of the set of trials and direction for best recommended practices.

Farmer survey of biological interest will set the stage for representing and selecting biologicals that are of interests to Indiana. Leaf nutrition will provide a snapshot of the nutrient responsiveness of soybean to the various biologicals. Multiple leaf samples and the interaction of nitrogen and sulfur will provide contrasting fertility to determine biologicals impact on soybean nutrition. The representation of varying soil types and field conditions will enable us to determine the situations when plant nutrition and soybean yield can be improved with various biologicals within several categories. We will also continue to observe the studies later in the season (e.g., digital imagery) to determine if leaf retention is an underlying source of yield improvements with greater supply of N.

The overall deliverables will be determining soybean yield responsive treatments followed by understanding why treatment did or did not provide a response from the soybeans. These recommendations will be conveyed through written and vocal Extension avenues.

The results from 2023 trials will be presented at Extension winter workshops, meetings, and conferences of producers, Extension educators, and crop professionals across Indiana and the country. We will also share these findings with our newsletter, podcasts, and at the American Society of Agronomy meetings. Other communication partners include Hoosier Ag Today with our Purdue Crop Chat where we can track the number of impressions when this content is shared. Collaborations with other Extension soybean agronomists from the Science for Success team also aligns with wider communication as well as impact.

The short-term benefits to farmers are to determine the opportunities to improve nutrient management from better use efficiency to providing another source of nutrition that may be cost effective. Fertilizer inputs are the highest variable cost in soybean production at 31% followed by seed at 23% and pesticides at 20% (Langemeier et al., 2022). Long-term benefits are to provide multiple approaches for managing fertility for optimal yields and profitability under various soil types and conditions while also decreasing nutrient applications. The latter has direct impact on profitability as well as environmental sustainability.

Lasting Impact - We have collaborated with soybean agronomists across the country to develop a common set of biological seed treatments in 2022 as a preliminary evaluation (e.g., Science for Success). Our expansive evaluation (this project) and targeted N supplying biological (this proposal) will allow us to select a few of the treatments (methods and/or biological category or product) that could be implemented in field-scale trials across Indiana in the following years. We could similarly develop a national protocol to continue to build the database for biological responsiveness.