3 In-Season Foliar Strategies to Boost Corn and Soybean Yields

After planting: how to protect crop productivity with foliar spray products

By: Dave Dyson, Locus AG Lead Agronomist

With planting wrapped up across the Midwest and South, growers are shifting focus to what comes next. From extreme heat to saturated soils, we’re once again being challenged by whatever Mother Nature throws our way. This year’s erratic weather across the corn and soybean belt has left crops at varying growth stages, making in-season management more complex. While seed treatments, inoculants and at-plant soil amendments lay the groundwork, the real difference-maker is how crops are supported throughout the rest of the season. Farmers need a product that’s proven to work across multiple growth stages and consistently boosts yields.

As corn and soybean crops start to stretch their legs, one of the most effective tools to combat an unpredictable growing season is a well-timed foliar program. Foliar spray applications can provide targeted nutrients and stress-fighting compounds right when plants need them most—especially when root uptake is limited by poor soil conditions.

In this blog, we’ll layout the three most critical stages where a foliar application can dramatically improve performance—and introduce a premium foliar-applied program designed to enhance photosynthesis, increase plant vigor and boost yields under stress.

Stage 1: Use a Foliar Application to Build Early Vigor (V3–V6 in Corn)

Strengthen the foundation before yield is determined

The early vegetative phase is when corn begins “building the factory” that will later fill the ear. During this critical stage, the crop is rapidly developing its root system, expanding leaf area and building energy reserves—making it especially vulnerable to stress. What many forget is that key yield components are already being set by V6, particularly the number of kernel rows around the cob.

Start by Determining the Correct Corn V Stage

The corn plant experiences multiple stress periods during its first six weeks after emergence. You might ask: How do I know when these stress periods will happen? The answer lies in understanding the biology of the corn plant.

Once emerged, corn typically gains one leaf stage per week. However, internode expansion may vary depending on growing conditions, so corn development should never be judged by height alone. Instead, always count the leaf collars to determine the V stage (see figure 1). This is especially important, as by V6, the plant has already determined the maximum number of kernel rows—making this a decisive moment for yield potential.

Figure 1: This picture shows the different collars or V stages of the corn.

That’s why this stage is an ideal time to apply a foliar-applied product containing fermentation-derived biosurfactants, known as sophorolipids, metabolites and organic acids. These compounds work together to support photosynthesis, improve plant vigor and ultimately, increase yield.

The result? Stronger roots, faster early growth and more energy for long-term yield development. 

READ MORE: OPTIMIZING CORN GROWTH STAGES

Stage 2: Enhance Reproductive Development with a Foliar Application (V10–VT in Corn / R3 in Soybeans)

Support crops through the most yield-critical window

We cannot let up on the gas pedal during the mid-season. As corn approaches V10, it enters a crucial reproductive development phase where the length of the ear is determined. By VT, the plant is preparing for pollination—a period when stress can severely reduce kernel number and size.

Figure 2: This picture shows a soybean plant at the R3 stage. Count down from the top of the plant 4 nodes and the forming pod should be ¼ inch long.

Soybeans, on the other hand, hit their reproductive tipping point at R3 (see figure 2), when they decide whether to keep or abort developing pods. If stressed, the plant will self-limit its yield potential.

In both cases, a targeted foliar application can provide the boost needed to get through this important stage.

Stage 3: Support Late-Season Seed Development with a Foliar Application (R4–R6 in Corn / R3–R5 in Soybeans)

Maximize grain fill and final yield potential

The final decisive window is often overlooked: late-season stress during seed fill. From R4 through R6 in corn, and R3 to R5 in soybeans, these crops allocate resources to developing and finishing grain. Stress during these stages can cause kernel abortion in corn and pod loss or reduced seed size in soybeans—directly impacting yield.

Applying foliar products during this final window provides crops with the hormonal and metabolic support needed to finish strong. Certain foliar products can enhance nutrient flow and plant energy during grain fill, which improves:

• Seed size and weight
• Final test weight
• Yield consistency across the field

How to Choose the Best Foliar-Applied Product

Elevate in-season performance with a proven foliar solution

Applying at the right stage is critical—but choosing the right foliar product is just as important.

With so many foliar products on the market, it can be hard to separate high-performing options from “me too” or commodity inputs. Not all foliar products are created equal, and very few are backed by real in-season yield data. When selecting a foliar input, growers should look for products that are scientifically proven to deliver mid-season benefits under real field conditions—not just lab claims.

That’s why many growers are turning to Bombigro^®, a new premium foliar-applied product developed by Locus Agriculture (Locus AG). Unlike conventional inputs, Bombigro is developed through a proprietary fermentation process. It contains a unique combination of sophorolipids, citric acid and yeast metabolites that are rapidly absorbed through the leaf surface, delivering fast-acting support during critical growth stages. It’s an ideal addition to any program—helping growers overcome external stress factors, improve crop vigor and unlock greater yield potential.

Farmers See Proven Yield Increases with Bombigro^®

Growers using Bombigro alone have reported impressive increases in corn and soybean yields:

• +10 bu/A in corn
• +3.4 bu/A in soybeans

And, when used as part of a treatment program with Locus AG’s soil-applied biologicals, data confirms the performance is even stronger:

• +14.1 bu/A in corn
• +7.5 bu/A in soybeans

Using Bombigro as a foliar product is a powerful tool for overcoming the stress and unpredictability of mid-season conditions—one that’s easy to apply and fits into standard spray programs.

DOWNLOAD: BOMBIGRO FOLIAR PRODUCT SHEET

How to Apply Bombigro through Foliar Application

One of the reasons growers are making the switch to Bombigro is its ease of use and flexibility across both crops and application methods. Whether you’re using a ground rig, drone or airplane, Bombigro is designed to fit seamlessly into your existing foliar program—with no complicated mixing or special equipment needed. It performs exceptionally well under low-volume conditions. Bombigro is also on Corteva’s list of compatible products for tank mix with Enlist and Enlist Duo.

Corn Foliar Application Timing and Benefits

In corn, Bombigro can be applied at two key stages for maximum benefit:

• Early vegetative stage (Before V9): Apply 1 gallon per acre to enhance early vigor, boost root development, and support the formation of kernel rows around the ear. This timing lays the foundation for stronger, more resilient plants heading into reproductive development.
• Reproductive stage (After VT): Apply 1 gallon per acre to support ear length development and reduce stress during the critical pollination window. This stage is ideal for pairing Bombigro with a fungicide application, making it easy to integrate into existing aerial or ground passes.

Soybean Application Timing and Benefits

For soybeans, the optimal timing for Bombigro is the R3 stage, when the plant begins forming pods:

Apply 1 gallon per acre when a ¼-inch pod is visible at the 4th node from the top of the plant. This timing is critical for helping the plant retain pods and develop more uniform, higher-quality seeds—especially under weather stress and poor soil conditions.

Drone or Aerial Applications

Bombigro foliar prouct being applied with a drone on corn at the V8 growth stage outside of Mexico, IN.

For drone or aerial applications, Bombigro can be used undiluted or mixed at a 1:1 ratio with water.

Whether you’re running a high-volume sprayer or precision drone application, Bombigro mixes easily and holds up in the tank—making it a simple yet powerful tool for improving crop productivity and yield across the season.

Don’t Let Up After Planting

Planting may be done, but success is far from guaranteed. The post-emergence and reproductive phases of the season are full of opportunity—but only if you manage them proactively.

With erratic weather, saturated soils and mounting crop stress, foliar nutrition has never been more important. A well-timed foliar program anchored by Bombigro can help you overcome challenges and turn a marginal crop to an exceptional one.

Contact your local Locus AG rep today to learn how Bombigro fits into your mid- and late-season corn or soybean strategy.