Objective 1. Quantify soybean foliar disease severity in response to fungicide treatments applied through irrigation.

Objective 2. Compare efficacy of soybean foliar disease management in ground rig versus irrigation applied fungicides.
All of the work in this study will be conducted at the University of Delaware’s Warrington Irrigation Research Farm in Harbeson, DE. A soybean variety will be selected and planted late April- early May at 140,000 seeds per acre. Using a combination of soil electro-conductivity mapping, aerial imagery, soil borings and historical yield maps, the field will be divided into 5 tiers (replications) of varying soil type (Tier 1 = 20% wettest/heaviest soil – Tier 5 = 20% driest/lightest soil). Within each soil type tier, the research field will be divided into 11 randomized treatments and 5 replications for a total of 55 individual 90’ x 90’ plots. Fertilizer will be applied based on the University of Delaware recommendations for irrigated soybean production. Weather data will be collected by a Delaware Environmental Observing System weather station located on the irrigation research farm.

Each plot will receive one of the following fungicide treatments via chemigation/fungigation or ground rig application and will be replicated five times:
1. No Fungicide
2. Miravis Top applied at R3 via fungigation
3. Miravis Top applied at R5 via fungigation
4. Miravis Top applied at R1 and R3 via fungigation
5. Miravis Top applied at R3 and R5 via fungigation
6. Miravis Top applied at R1 + R3 + R5 via fungigation
7. Miravis Top applied at R3 via ground rig
8. Miravis Top applied at R5 via ground rig
9. Miravis Top applied at R1 and R3 via ground rig
10. Miravis Top applied at R3 and R5 via ground rig
11. Miravis Top applied at R1 + R3 + R5 via ground rig

For foliar pathogens that are present, disease severity ratings will be collected throughout the season at various growth stages. We anticipate that foliar disease pressure may be low, but that differences in Septoria brown spot could be present. Although not historically associated with yield loss, recent trials in DE and further south have shown yield loss when Septoria brown spot moves up the canopy earlier in the growing season. Plots will be harvested with a plot combine to determine yield, moisture, and test weight differences. Disease ratings and yield data will be analyzed to determine treatment differences among fungigation and ground rig application methods and timings. Fungicide cost as well as application frequency will be analyzed for economic implications of each treatment. Data from this trial will be used to measure disease severity and yield response to assess potential of applying fungicides through irrigation for soybean diseases in the Mid-Atlantic.

Objective 3. Disseminate research results to Mid-Atlantic irrigated farmers.
Findings from this project will be shared through the University of Delaware’s Weekly Crop Update which reaches over 700 growers, consultants, and stakeholders and provides a platform to discuss disease concerns and other production issues. Data will also be shared through training events and extension presentations such as Mid Atlantic Crop School, and the 2023 Delaware Ag Week.

Update:

View uploaded report

Center pivot irrigation is widely used across the Mid-Atlantic. Irrigation research has historically been conducted in the semi-arid Southwest US, with limited adaptability to Maryland and Delaware due to climate and soil differences. In recent years there has been an effort to optimize irrigation practices specifically for the Mid-Atlantic. As improvements are made in irrigation timing and nutrient management, new questions, such as the addition of fungicides to irrigation, have been raised. The application of fungicides through irrigation has not been widely investigated in the Mid-Atlantic, but could provide an additional application method to farmers. Project objectives included: 1) Quantify soybean foliar disease severity in response to fungicide treatments applied through irrigation. 2) Compare efficacy of soybean foliar disease management in ground rig versus irrigation applied fungicides. 3) Disseminate research results to Mid-Atlantic irrigated farmers. In 2022, disease pressure was limited with insufficient disease levels to take severity ratings. Ground rig applications had higher NDRE values indicating higher chlorophyll content in plants receiving fungicide application by this method. Although there were visual differences in NDRE, no effect on yield was observed. Further replications of this experiment will be conducted in 2023 to gain additional data comparing fungicide application by ground rig versus fungigation at various timings in soybean. The goal of this project is to assess the efficacy of fungicides applied via fungigation in comparison to ground rig applications at multiple application timings to inform application method recommendations for soybean farmers.