Month: April 2026

Christopher LeMaster, Jr.
Livestock & Forage Agent
Cherokee, Spartanburg, & Union Counties

We don’t usually associate tall fescue with nitrate toxicity in the spring. However, the current D3 drought conditions have changed the equation. This is not only a “summer problem,” but cool-season grasses—such as tall fescue or winter annuals—can pose a risk under these specific conditions.

If you applied high levels of nitrogen this spring to catch a flush of growth that never came, the risk in your fescue fields is real. Without rain, the plant couldn’t convert that nitrogen into growth. It simply accumulated in the lower portion of the plant. Now that we are finally seeing some rain, that “stuck” nitrogen is being pulled into the plant at a rapid rate.

The Spike

It is a common misconception that the danger passes as soon as the grass turns green again. In reality, research shows that nitrate levels typically spike 2 to 3 days after a drought-ending rain. This is the most dangerous window for your livestock.

• The One-Week Rule: While the spike is most acute in the first 48 to 72 hours, we recommend waiting at least one week before grazing or harvesting. This allows the plant time to resume normal metabolism and begin “growing out” of that initial nitrate flush.
• Hay is “Locked In”: Nitrates do not dissipate in dry hay. Once your mower hits the field, you are locked in at that nitrate level forever.
• Silage/Fermentation: If you are putting up high-moisture forage or baleage, the fermentation process can reduce nitrate levels by 40% to 60%, but this should still be verified with a test.

Don’t Guess—Test

If you have fields with a high nitrogen history that are currently recovering from drought, I strongly recommend sampling the standing forage before you cut.

• Get a Representative Sample: Take “grab samples” from multiple areas of the field, specifically focusing on the lower portions of the plant where nitrates concentrate.
• Utilize the Lab: Bring your samples to your local Extension Office or send them directly to the Agricultural Service Laboratory. They can provide a precise analysis of nitrate-nitrogen levels.
• Check the Backlog: We may also consider testing outside of that initial one-week window. Once the plant has had time to work through the backlog of accumulated nitrogen, a follow-up sample can confirm if the forage has returned to an acceptable or safe range for harvest.

Next Steps

If your test results come back with an elevated nitrate level, we can work on a plan to safely manage that forage. Whether that means diluting the feed with other forages, adjusting your grazing strategy, or simply waiting a few more days for the plant to balance out, there are ways to keep your herd safe.

Have questions about how to pull a proper sample or interpret your lab results?
Reach out to your local livestock and forage agent today.

Spray or Delay?

Spring arrived ahead of schedule this year, catching many producers off guard with the advanced maturity of our common winter weeds. While most of these species are typically easy to control when targeted at the correct growth stage, the recent unseasonal warmth has given them a significant jump start. Now, many of us are looking at advanced weeds and wondering: should we spray now or delay?

The Current Challenge

However, even the best-laid plans are subject to the weather. The lack of rainfall of this past fall persisted through the winter and into the spring, complicating management decisions.

The Trade-Off: Chemical Power vs. Plant Maturity

It’s tempting to look at a field of mature henbit and mustard and want to reach for a heavy hitter. Many would agree that a strong residual herbicide—such as those containing aminopyralid (like GrazonNext® HL)—would work even on these mature plants.

While you are likely right about the efficacy, we must factor in the maturity of the forage stand. Most high-powered herbicides require the grass to have at least three leaves and a healthy root system before application. This particular stand was just barely above that maturity threshold, and it seemed risky given the current drought conditions and warmer temperatures.

The “Mow vs. Spray” Decision

Beyond plant maturity, there is the critical factor of residual restrictions. Herbicides containing aminopyralid carry a significant restriction: the hay cannot be sold off the farm for 18 months. For many hay growers, this necessitates a non-residual herbicide approach.

However, at this stage of maturity, a non-residual option like 2,4-D would not provide adequate control. By this point, much of the damage—the robbing of water, sunlight, and fertilizer—has already been done by these mature weeds. While it is always satisfying to spray and watch the weeds curl and die, the current drought makes it a real challenge; we need actively growing weeds for maximum herbicide uptake.

In this case, the decision was made to wait and mow the field at a high height. This strategy offers several benefits:

• Stimulating Growth: Set the mower high to encourage some regrowth and tillering while also avoiding the energy reserves and some canopy.
• Nutrient Cycling: It leaves the nutrients in the field to break down rather than removing them in a hay crop.
• Recovery Time: A traditional hay crop is often cut shorter and later in the season, which wouldn’t allow the plant to rebound as quickly before the summer months.

Looking Ahead: Planning for Next Season

The main goal of this situation was to prepare and protect the plant for its biggest hurdle yet: summer. The fescue needs maximum root development to survive the heat and lack of rain.

As we plan ahead for next season, it’s important to remember that many of these winter weeds can be successfully controlled much earlier. Targeting them in the fall, or even during late February and early March, allows for better control while the weeds are small and before they’ve had a chance to rob your forage of vital resources.

Moving forward, they are shifting to a more rigorous weed scouting program. By catching the summer weeds as they emerge, we can ensure they are controlled efficiently and cost-effectively.

As with anything, there is no one answer that fits for everybody. Spraying may still be the best option for your situation. Feel free to reach out, and let’s discuss a plan.

Christopher LeMaster
Area Livestock & Forages Agent
CLEMAST@CLEMSON.EDU