Non Technical Summary
Abiotic and biotic stressors can reduce corn and soybean plant population density. Earlier corn and soybean planting dates are more common now (aiming at higher yields), often resulting in lower plant populations. Depending on plant population and calendar date, farmers may choose to replant fields. Replanting costs time and money and should only be done if clearly needed. Farmers are anticipated to face replant decisions more frequently as they plant earlier, and the climate continues to change. Replant recommendations are outdated and do not reflect current production practices, crop genetics, or environmental conditions. The long-term goal of this project is to achieve more sustainable corn and soybean production systems with research-based replant guidelines. We will identify soybean and corn replant thresholds based on plant population and planting date (Objective 1), develop an Excel-based decision support tool to compare the profitability of replanting scenarios (Objective 2), and use novel Extension programming with biweekly outcomes for disseminating results to stakeholders (Objective 3). Our applied research observations will be documented and delivered to farmers in real-time through bi-weekly video updates, not at project completion. The outcomes of this project will directly advance the Program Area Priority of Plant Health and Production of Plant Products, ensuring continued production gains by identifying replant thresholds. If farmers unnecessarily replant, they may experience negative outcomes of yield loss and reduced profitability. This will help farmers make informed decisions during the growing season for immediate impact.

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
205	2410	3100	50%
205	2499	3100	50%

Knowledge Area
205 - Plant Management Systems;

Subject Of Investigation
2410 - Cross-commodity research--multiple crops; 2499 - Plant research, general;

Field Of Science
3100 - Management;

Goals / Objectives
Long-term goal:This integrated research and Extension project aims to achieve more sustainable corn and soybean production systems in the Midwest US by reducing soil disturbance and improving the use of resources and labor through informed, research-based replant guidelines.Objectives:1) Identify soybean and corn replant thresholds based on plant population and planting date,2) Develop an Excel-based decision support tool to compare replant scenarios based on current market prices and costs, and3) Create videos and newsletters to update stakeholders in real time and archive digital curriculum on a virtual learning management system for continued use by stakeholders.

Project Methods
Objective 1. Identify soybean and corn replant thresholds based on plant population and planting date. A field experiment will be conducted on corn and soybean during the 2025and 2026growing seasons at three locations in Ohio: the Northwest Agricultural Research Station in Wood County, the Wooster Campus in Wayne County, and the Western Agricultural Research Station in Clark County. This plan will result in a total of six site-year combinations on each crop. A separate field will be used for the corn and soybean experiments, but treatments and experimental design will be similar. The experiment will be a split-plot randomized complete design with four replications of each treatment. The main plot factor will be the planting date, and the subplot factor will be the seeding rate.A high-yielding, commercially available corn hybrid and soybean variety will be used for both years of the study. Cultivars will be selected using site-specific information from the Ohio Crop Performance Trials. Corn and soybeans will be planted in small plots (roughly 10 ft wide by 30 ft long). All planting dates of corn and soybean will be maintained according to state guidelines, which reflect farmer practices within the state. For each planting date, the corn and soybean population will be quantified by taking a stand count at the V2-V3 growth stage and physiological maturity. For corn and soybean, crop staging and canopy cover will be assessed weekly using the smartphone App, Canopeo. At the flowering stage of both crops, canopy characterization measurements (three ft length of row for soybean and five plants for corn) will be conducted to assess the impact of seeding rate and planting date, which would help explain productivity differences; these will include plant height in both crops, branch number for soybean, and leaf number for corn. Information on days from planting to flowering will be recorded for both crops, accounting for any length of days "compression" potentially experienced by later planted crops. At physiological maturity, soybean plants will be collected from a 3 ft length of row and plant height and branch number will be recorded along with soybean yield components (number of pods per plant, number of seeds per pod, and seed weight). At physiological maturity for corn, plant height and yield components will be estimated from a representative sample of five plants per plot (number of ears, kernel rows per ear, kernels per row, and kernel weight). At harvest, soybean and corn grain moisture, yield, and test weight will be measured using small plot research combines. Before statistical analysis, grain yield will be adjusted to 13% moisture content for soybean and 15.5% for corn. Plots will be harvested earlier or later depending on planting dates to minimize harvest losses.Field data will be analyzed using the PROC GLIMMX in SAS 9.4 to determine the planting date and seeding rate effect on the measured variables. We will also test for the year and location effect, as the replant threshold may vary depending on the growing environment. For both corn and soybean, we will generate a yield-based table for corn and soybean replant decisions.Objective 2. Develop an Excel-based decision support tool to compare replant scenarios with current market prices and costs. An Excel-based decision support tool will be developed using the field results of years 1 and 2 to compare replant scenarios with current market prices and costs. For the tool, we will estimate the partial return of corn and soybean based on various planting dates and plant population scenarios using field-based research. The gross return of each planting date and plant population scenario will be calculated by multiplying grain yield by crop price. Crop prices will be obtained from the USDA National Agricultural Statistics Service. Production costs and field operation costs for corn and soybean will be obtained from the Enterprise Budgets and Custom Rate Survey from Ohio State University. Profitability will be determined by subtracting costs from gross return.The tool will also include a place for farmers to add their own prices and costs from their farming operation.Prior to releasing the tool, we will work with stakeholders to validate our tools to ensure it is user-friendly and intuitive.Objective 3. Create videos and newsletters to update stakeholders in real time and archive digital curriculum on a virtual learning management system for continued use by stakeholders.We will publish a newsletter article and video bi-weekly throughout the growing season (April through September). The newsletter and video content will be related to field research and include real-time observations and recommendations. Videos will feature special guests, Extension state specialists, county Extension educators, farmers, and graduate students. Newsletter articles will be published through the Ohio State University Extension AgCrop's Team C.O.R.N. newsletter (corn.osu.edu), and videos will be hosted on the AgCrops Team YouTube channel (https://www.youtube.com/@OSUAgronomicCrops). We will use a variety of formats for the videos, including footage from the field, interviews, and greenscreen technology. Video footage will be captured with a cell phone, stationary tripod, and an external microphone system for higher content quality. Videos will be edited using Adobe Premiere Pro software.Evaluation Approach.During the project's third year, we will collate videos into 30-minute segments to create a curriculum for farmers and Certified Crop Advisers (CCAs). Our curriculum will aim to have five learning concepts embedded 1) definition of learning objectives, 2) listing of the prerequisite knowledge necessary, 3) three different styles of presenting learning content, 4) permitting the learner to control the pace and direction of the lesson, and 5) provisions for testing and feedback.The curriculum will be web-based to deliver quality distance education. We will use the learning management system Scarlet Canvas to develop the learning modules (http://canvaslms.com). The College of Food, Agricultural, and Environmental Sciences at Ohio State University has a license for Canvas that can be used to develop and manage web-based learning modules free and open to the public. Each 30-minute video segment will have an 8-10-question quiz based on the video content. CCAs may take the quiz for the opportunity to earn continuing education units (CEUs), which are required to maintain their certification. After the course, participants will be asked to fill out a survey instrument to document changes in knowledge and to gather stakeholder input on the effectiveness of the curriculum.