As crops push into peak growth stages, the window for in-season nutrient applications is open. Taking a proactive, data-informed approach to nutrient decisions during the season can increase yield, reduce environmental risk and increase economic resilience.
“We often focus so much on what goes down pre-plant that we forget the crop’s biggest appetite hits mid-season,” said Steve Carlson, director of proprietary products for CHS. “It’s like giving your crop breakfast and expecting it to power through the day without lunch or dinner.”
Timing and Testing
Natalina Sents Bausch
Corn nutrient demands surge around V10, making the period leading up to and during rapid vegetative growth ideal for supplementing with in-season nutrients. For soybeans and wheat, reproductive stages mark the point of highest demand. The key is to be proactive rather than reactive, Carlson said.
“You don’t want to wait until you see yellow leaves or stunted growth,” Carlson said. “By the time visual symptoms appear, it may already be too late to correct.”
Pairing soil tests with multi-year, on-farm trial data can help growers make more informed nutrient decisions, said Stephanie Zelinko, an agronomist for AgroLiquid. She uses a “win rate” approach to quantify the likelihood of both yield response and economic return from specific in-season applications.
“A win rate tells you the chance that a given nutrient application will provide a yield bump and whether that yield pays for the fertilizer,” Zelinko explained. For example, AgroLiquid’s foliar soybean applications have a 90% yield win rate and about a 72% economic win rate under current market conditions.
“That means 7 out of 10 times, the yield gain not only pays for the fertilizer but leaves extra profit,” Zelinko said. Below 70%, Zelinko advises growers to reevaluate the economics of an in-season application factoring in soil tests, local prices, and crop conditions to make sure the application makes financial sense.
Micronutrient Impact
While nitrogen, phosphorus, and potassium dominate many fertility conversations, Carlson urged farmers not to overlook the other 15 essential plant nutrients.
“Zinc and boron are the two most deficient micronutrients in U.S. ag soils,” he said. “And they’re two of the most responsive, especially when applied in-season.”
Carlson pointed to copper’s role in small grains, supporting stem strength and disease resistance, and boron’s effect on early root development and later pollination success in soybeans and corn.
Zelinko added that even when a soil test shows adequate levels of key nutrients like potassium, in-season foliar applications can still enhance uptake and performance during reproductive stages. “Soybeans thrive on potassium, and they’ll respond to that foliar supplement even in well-fertilized fields,” she said.
Tools for Precision and Profit
Zelinko and Carlson agree that today’s technology makes it easier than ever to document and analyze nutrient trial results. Yield monitors can isolate the effect of specific applications, and spreadsheet-based tools allow growers to plug in their local crop and fertilizer prices to calculate their own win rates.
Tissue testing can also play a role, especially when used consistently over time and in conjunction with soil test data. “It’s like a snapshot of the plant’s health,” Zelinko says. “But you can’t rely on a single test. Use it as part of the bigger picture.”
Building a Flexible Plan
Input costs remain high, and with crop prices fluctuating, both Zelinko and Carlson advocate for flexible fertility plans that leave room for adjustment based on in-season crop conditions.
“Don’t commit every dollar upfront,” Zelinko advised. “If the weather holds and the crop looks strong, you can layer in nutrients later. But if it turns dry or you get hit with insect pressure, you’re not over-invested.”
When budgets are tight, Carlson recommended narrowing in on the nutrients with the highest potential return — zinc and boron for most crops — and ensuring macronutrients are supported by the right micros for full uptake. “If you’re cutting back on macros, your micros matter more,” he said.
Targeted Nutrition for Better Returns and Fewer Losses
Timing fertilizer applications to crop demand doesn’t just help your budget, it can help reduce runoff and nutrient loss, too.
“The longer nutrients sit in the soil before a crop uses them, the more risk there is for volatilization, leaching, or runoff,” Carlson said. “Applying closer to when the plant needs it reduces that risk and boosts efficiency.”
Zelinko notes that applying nutrients using the 4R framework (right rate, right source, right time, and right place) can help improve efficiency and reduce environmental risk. “We’ve been focused on high-efficiency products for a long time,” she said. “And the more targeted your applications, the better your ROI and environmental impact.”
Active and Flexible Strategies
Both agronomists agree that the biggest mistake farmers make with in-season fertility is assuming early applications are enough.
“There’s a lot happening in that plant after the V5, V6 growth stages, especially as it shifts into reproductive growth,” Carlson said. “Don’t miss the opportunity to feed it when it matters most.”
“Your soil test is your starting point,” Zelinko said. “But you’ve got to tie it to real world economics and your own farm’s data. In-season applications give you that flexibility to feed the crop, protect your investment, and ultimately maximize returns.”