Iron Deficiency Chlorosis (IDC) is one of the most yield damaging maladies of soybean in western Minnesota. Farmers valiantly battle IDC with a wide range of strategies to reduce losses. Crop rotations, variety selection, seeding rates, rows spacing, iron chelates, tillage, drainage, and even cover crops or companion crops are utilized today. However, each of these strategies comes at some cost. Today’s most tolerant IDC varieties come with some yield penalty relative to varieties sold elsewhere. Increased seeding rates significantly reduce IDC, but soybean seed has become increasingly expensive. Iron chelates have been a game changer for soybean producers in the most heavily affected areas but are quite costly at effective rates.
This study is designed to examine three of the most often used management strategies for IDC from a systems approach: variety selection, seeding rate, and iron chelates. We will examine tradeoffs in cost and yield response to these strategies across a wide range of IDC levels. Coupled with an economic analysis, this work will allow us to provide producers with more refined recommendations for managing IDC to support them in their efforts to achieve the greatest economic return on every farm. In addition, we are working with Bayer Crop Science to develop complementary research projects with Bayer Technology Development and Climate to extend this research to additional locations and at field scale.
This collaboration will also allow us to extend dissemination of research findings through the entire Bayer network in addition to University and MS&PC’s networks.

Iron Deficiency Chlorosis causes significant yield losses for Minnesota soybean producers across much of western Minnesota. While farmers can reduce risk of major losses and can minimize field-level yield declines, management strategies for IDC come at significant expense to the producer. In addition, there are clear trade-offs between managing soybean with varieties, iron chelates, and populations. We know increased rates of iron chelates increases soybean yields under IDC, yet we know little about rates required to support higher-yielding, but less IDC tolerant varieties. Some very high-yielding varieties are known to produce high field-level yields, even though they may suffer significantly in IDC areas. Yet, most producers tend to take the justifiable conservative approach by planting the most IDC-tolerant variety, utilizing moderate rates of iron chelates, and increasing seeding rates. But what is the best strategy - economically?

The objectives of this work are to 1) determine what combination of genetic tolerance, rate of iron chelates, and soybean population produces the greatest yields based on IDC intensity, 2) identify the optimum economic return of these management strategies across ranges of IDC, and 3) collaborate with Bayer to leverage this research investment into a large and synergistic project involving strip trials and field-level evaluation of these management strategies, and to utilize Bayer’s network to disseminate research findings more broadly.

Goal 1: Examine tradeoffs and interactive effects between varieties, populations, and iron chelate rates across a range of IDC levels.
Objective 1: Examine each of the three factors individually across a range of IDC levels.
Objective 2: Examine all two- and three-way interactions between these factors.
Objective 3: Examine interactions to define relative effects of each factor on yield.

Goal 2: Develop an economic model informing producers about ROI for each management strategy individually and collectively, to maximize economic returns across fields and farms.
Objective 1: Utilize yield response data against a range of grain prices and input costs to define optimum combinations of these three factors for IDC management - farm-wide.

Goal 3: Collaborate with Bayer to leverage investments into research and outreach activities supported here.
Objective 1: Coordinate with Bayer Technology Development team to develop identical treatments across platforms for data sharing. Bayer will put out multiple on-farm trials in the Benson area with medium-scale precision planting equipment.
Objective 2: Coordinate with Climate to develop identical treatments that can be placed on-farm with farmer cooperators broadly across Minnesota.
Objective 3: Coordinate throughout the season to capture weekly drone imagery, ground-based measurements, and yield data from small plots, strip plots, and field-scale research studies.

This proposal covers the deployment of six small-plot research studies on three cooperating famers’ fields. To vary the intensity of IDC, small-plot studies will be located in a ‘hot-spot’ on each producer field as well as in an area of each field that is representative of the majority of the acres in that field or less chlorotic. We have developed an efficient protocol whereby we are able to increase the intensity of IDC symptoms through the application of supplemental N. Therefore, in addition to the primary treatments, each study will be blocked with and without supplemental N application.
In total, we will therefore replicate this study across 12 unique IDC environments (3 fields, 2 areas within each field, and 2 levels of IDC intensity within each study area). With four replications, we are planning for 768 individual plots.

• 2 Variety treatments
o Moderately tolerant
o Highly tolerant

• 2 Populations
o 125,000
o 175,000

• 4 Iron Chelate (SoyGreen) rates
o 0
o 2 lbs
o 3 lbs
o 4 lbs

• 2 IDC levels
o With N
o Without N

• 2 Locations within fields
• 3 Producers

Three cooperating producers will be selected to represent district IDC environments so that unique soil and climate factors are examined annually to allow a broad inference of research findings. The six field studies will be planted in production soybean fields by the Naeve project. A split-block design will be utilized, where N rate will be a main block and varieties and populations will be randomized within the first split, iron chelate rate.
After emergence, plots will be evaluated weekly for IDC systems through visual scoring, ground based NDVI as well as though high-resolution drone imagery. These data will be utilized to evaluate each treatment for timing and intensity of IDC symptomology relative to yield.
Upon completion of field activities, a complete economic analysis will be conducted. Yield data will be examined relative to a range of grain prices and appropriate input costs. Economists will be consulted on the more appropriate analyses based on the recorded data.

Update:
All-in-all, we had very good luck this year with this field study, despite weather challenges.

Graduate student Maykon da Silva began his MS program in the Naeve lab in January, of 2021. He chose this study to lead through his degree program, thesis writing, defense, and publication. Maykon is an excellent student and will see this project through to its completion.

We were able to secure three unique and distinct research sites in Western MN. These on-farm sites were located near Danvers, Graceville, and Foxome. At each site, two studies were planted – one on a known IDC ‘hotspot’ and one planted within the same field without a history of significant IDC loss.

In addition, we are cooperating with Bayer Crop Science on this project. They put out similar studies on their research farms in WC MN in 2021. We expect to meet with them to discuss findings and share data later this winter.

A poster describing some preliminary results from this trial are attached here. This poster was presented at the recent international Agronomy meetings held in Salt Lake City, November 7-10, 2021.

Below are a few of the key activities carried out at these research sites.

5-8-2021 – Foxhome -- Planted
5/10/2021 – Graceville -- Planted
5/11/2021 – Danvers -- Planted
5/18/2021 – Three sites – urea applied
9/10/2021 – Danvers and Graceville – plant heights
9/28/2021 – Foxhome – plant heights
9/30/2021 – Foxhome – harvest
10/19/2021 – Danvers and Graceville -- harvest

Weekly from VE until R6
- Visual IDC ratings
- Ground based NDVI (by CropCircle)
- Drone based high resolution – multispectral imaging

Challenges:
One significant challenge involved harvest. Despite severe drought all year, two sites were struck by several significant multi-inch rainfall events in early October. This delayed harvest at both Danvers and Graceville. In addition, excess water at Graceville kept us from harvesting a handful of plots in one study area. No studies were lost, but harvest was delayed and a few plots were lost.

View uploaded report

Update:

View uploaded report

Managing Iron Deficiency Chlorosis with Agronomics and Economics
Maykon da Silva and Seth Naeve

Abstract
Iron Deficiency Chlorosis (IDC) is a major yield-limiting stress for soybean [Glycine max (L.) Merr.] grown on the calcareous soils of the U.S. upper Midwest. During the 2021 growing season, six on-farm research trials were established at three locations in Western Minnesota (Graceville, Foxhome, and Danvers) on two IDC-prone field areas (hotspot vs. non-hotspot) to evaluate the effectiveness of three of the most often used management strategies for IDC from a system’s approach: variety selection, seeding rates, and iron chelates. Three Fe-EDDHA rates (0, 2 and 4 lbs. Soygreen? acre-1) were applied in-furrow at the time of planting either a highly tolerant (AG13XF0) or a moderately tolerant (AG12XF1) variety at 125,000 and 175,000 plants acre-1. Nitrogen was supplied to create a range of IDC symptomology. Visual chlorosis scores (VCS), drone imagery, and ground based NDVI were assessed as methods for measuring the severity of symptoms. Our preliminary results suggest different management strategies to be recommended depending on the field location and the intensity of IDC symptoms. At Graceville non-hotspot, the application of Soygreen? increased soybean yield by 54 to 60% in the susceptible variety where IDC was amplified by N addition. At Graceville hotspot, regardless of variety, Soygreen? application increased yield by at least 35 bushels when N was applied. Where N was not applied and no Soygreen? was added, the highly tolerant variety yielded 72% more than the moderately tolerant one. At Foxhome non-hotspot, the yield of the moderately tolerant variety was decreased by 25% when N was added. At Foxhome hotspot, the highly tolerant variety produced 28% more than the moderately tolerant variety when IDC intensity was not increased by N application. At Danvers non-hotspot, there were no differences in grain yield between treatments. Differently, at Danvers hotspot, three main things were found. At higher seeding rate treatments, the application of 4 lbs. Soygreen? acre-1 significantly increased the yield of the moderately tolerant variety. Without Soygreen? applied, increasing the seeding rate of the highly tolerant variety from 125,000 to 175,000 plants acre-1 resulted in a yield increase of 36 bushels. At increased seeding rates and without Soygreen? application, the highly tolerant variety produced 52% more than the moderately tolerant one. Overall, variety selection, increased seeding rate, and in-furrow application of iron chelates were effective in controlling IDC and minimizing yield losses. Further research will evaluate the impact of these three management strategies individually and collectively on return on investment. Coupled with an economic analysis, this work will provide producers with more refined recommendations for managing IDC and will support them in their efforts to achieve the greatest economic return on every farm.