Nitrogen is typically the most limiting nutrient for grass growth, but more isn’t always better. This article will cover some considerations for managing nitrogen after first-cutting or post-grazing.
Most Ohio forage grasses on loamy soils see economic returns on up to around 150 lbs N/ acre / year. Returns improve when (a) N is split into ~3 applications, (b) each application is below 80 lbs/ acre, and (c) applications are made shortly before rainfall. Rates should also be decreased for fields with proportions of legumes (see Table 7.9 from the Ohio Agronomy Guide, below).
We’ve traditionally recommended the highest N rates (~80 lbs/ acre) be applied at green-up, followed by around 50 lbs/ acre after each cutting. This pattern helps provide nutrients at the times when cool-season grass growth is the fastest, maximizing forage production. But, that large amount of early-season growth is only an asset if we have a way to use it via grazing or storing, and in recent years our wet spring weather has made it harder for folks to turn out animals or make first cutting hay made on time. When you reduce or skip an early-season N application, timely application of N after the first cutting is increasingly important.
Urea, and most of our commonly available N sources, can volatilize in hot, dry weather. Applying N shortly before a rainfall event reduces volatilization, and the water in soil is necessary for plant roots to take up nitrogen. I think the significance of water is important to mention, since many older forage/ grazing management guidelines include the phrase “use nitrogen strategically to increase grass growth during certain seasons”—this only works when nitrogen availability is more limiting than water availability, and fertilizer cannot increase growth when dry weather is the main factor reducing plant growth!
Speaking of volatilization, lime can cause urea to volatilize more than it would otherwise. Never spread lime and urea at the same time, and check your recently limed fields before making urea application decisions. It takes 4-6 months for lime to react in the soil, and the unreacted lime sits on the soil surface in pastures and other no-till systems. If lime is visible on the soil surface of pastures that got limed this fall, response to N this summer will be limited and urea application may not be worth the investment. This is especially true in years like 2026 when N prices are high, and the fuel costs for applications are also high.
Need a simple place to start? Return on nitrogen will likely be highest on fields that did not get limed in the last 6-12 months and has <20% legumes. In those situations, consider applying around 50lbs of N per acre in the 1-2 weeks after cutting, when rain is in the forecast. Lower your N rate for fields with more legumes, and consider skipping an application on recently limed fields or in very dry conditions.
Other Resources:
Ohio Agronomy Guide: https://extensionpubs.osu.edu/ohio-agronomy-guide-16th-edition-pdf/
Nutrient Management of Forage Crops Intended for Hay: https://ohioline.osu.edu/factsheet/anr-0109