Research on irrigation of agronomic crops in the Mid-Atlantic region has been limited until recent years. Delmarva farmers have been experimenting with fungigation for over 2 decades with few, if any, replicated studies. Adkins, Whaley & Sylvester explored fungigation of corn at the UD Warrington Farm in 2018 to evaluate the accuracy of the chemigation system and provide initial data for setting up more advanced tests. This work was continued by Koehler and Adkins from 2019- 2021, where it was shown that fungicides applied through irrigation reduced disease severity of grey leaf spot in corn, with variable yield effects. To date, there have been no replicated trials assessing efficacy of fungicides for foliar diseases of soybean when applied through irrigation.

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.

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 Neo applied at R3 via fungigation
3. Miravis Neo applied at R5 via fungigation
4. Miravis Neo applied at R1 and R3 via fungigation
5. Miravis Neo applied at R3 and R5 via fungigation
6. Miravis Neo applied at R1 + R3 + R5 via fungigation
7. Miravis Neo applied at R3 via ground rig
8. Miravis Neo applied at R5 via ground rig
9. Miravis Neo applied at R1 and R3 via ground rig
10. Miravis Neo applied at R3 and R5 via ground rig
11. Miravis Neo 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, Delaware Ag Week, and/or other winter soybean meetings.

Update:
Soybeans were planted at the Warrington Irrigation Farm on 6/1/23. Plots were divided into 90'x90' blocks to receive one of the following treatments:

1. No Fungicide
2. Miravis Neo applied at R3 via fungigation
3. Miravis Neo applied at R5 via fungigation
4. Miravis Neo applied at R1 and R3 via fungigation
5. Miravis Neo applied at R3 and R5 via fungigation
6. Miravis Neo applied at R1 + R3 + R5 via fungigation
7. Miravis Neo applied at R3 via ground rig
8. Miravis Neo applied at R5 via ground rig
9. Miravis Neo applied at R1 and R3 via ground rig
10. Miravis Neo applied at R3 and R5 via ground rig
11. Miravis Neo applied at R1 + R3 + R5 via ground rig

R1 applications for fungigation and ground rig were made 7/28/23. R3 applications are scheduled for early August and R5 will be initiated once the growth stage is research. After R5 application, plants will be rated for any foliar disease. We will also be using drone imagery to capture any differences in canopy visible from aerial view. Plots will be harvested to compare yields across treatments.

Update:

View uploaded report

The relatively flat topography and sandy soils of the Mid-Atlantic are ideal candidates for the center pivot type irrigation that is employed on over 85% of the irrigated acreage. Irrigation research has historically been conducted in the semi-arid Southwest US, but research from other areas of the U.S. often has 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, can be addressed.

The application of fungicides through irrigation has not been widely investigated in the Mid-Atlantic, but could provide farmers with the option for an additional application method. From 2019-2021, initial research on efficacy for management of foliar diseases in corn were conducted at the UD Warrington Irrigation Farm. This work has generated interest from growers to determine if fungicides applied via irrigation may also be viable in soybean production.