Crops
by Dr. Paul Tracy

Nitrogen can make hay
Prices bring scrutiny on fertilizing forage, but the practice can still pay

Nitrogen management of tall fescue hay and pasture fields has been a hot topic this year. Most of the discussion has been wrapped around fertilizer prices. Other issues such as feed/hay value, weed control, herd management, and legume establishment are completely intertwined and cannot be ignored.

For years, MFA’s agronomy program has promoted a systems approach to fescue-based forage management. This has included balanced fertility, pasture renovation, proper animal rotation, field prioritization and intra-pasture species diversification. That approach works best under longterm operational planning. My experience is that we rarely benefit from short-term responses to nonagronomically driven issues.

Tall fescue grows most rapidly in the spring, followed by the fall, with some growth occurring during the summer. To match this growth, most nitrogen fertilizer is traditionally applied in the late winter or early spring. This is especially important when spring haying is planned. Recently, there has been an appreciable shift in some or most of the total annual nitrogen being applied to tall fescue pastures in August. This stimulates fall growth, which is critical for winter stockpiling. By shifting to August we also avoid spring overproduction in fields that cannot be effi- ciently utilized or harvested during March through May.

Late-spring tall fescue nitrogen application has received much less attention. This timing often provides the most return per nitrogen dollar invested. It may provide enough growth for a second hay cutting and will certainly increase forage available going into the summer months, a time when cool season grass production usually decreases. May nitrogen is especially relevant this year, since many tall fescue fields did not receive adequate crop nutrient inputs from February through April.

For hay fields, when weather permits, tall fescue should always be harvested in May. If you plan to summer graze hay fields or attempt a second cutting, plan to add approximately 40 pounds of nitrogen per expected ton of forage produced. This application should be done immediately following hay harvest. The exception would be if legumes make up at least a third of your potential summer biomass.

In pasture situations, make sure any grass receiving May nitrogen is well grazed or clipped before application. If you have multiple paddocks, intensify nitrogen applications onto the fields to be utilized over the next 8 weeks and leave less pressured paddocks unfertilized until August.

This year there has been a huge push toward “replacing” fescue nitrogen fertilizer with clover/ legume seedings. Flexibility and responding to your personal needs and production environment should determine whether legume management or nitrogen inputs offer the best option. I have always been a strong proponent of aggressive legume management within our fescue fields. However, you cannot simply throw a few pounds of clover seed onto fescue fields and expect miracles.

This spring, we have heard many reports that legumes provide the equivalent of 150 to 200 pounds of nitrogen fertilizer per acre. There have also been many statements that legumes actively feed nitrogen directly to tall fescue. This information is often misinterpreted. In many cases, by following its logic, growers actually lower forage production and reduce net forage-based income. Legumes can only offset nitrogen inputs if field conditions are optimal for legume growth. Under many field environments, legume management means higher expenses compared to using nitrogen to stimulate tall fescue production.

Most fields that have not historically produced good legumes are that way for a reason. Many forage legumes require a higher soil pH and higher levels of soiltest phosphorus and potassium compared to tall fescue. At suboptimum pH levels, the rhizobium bacteria responsible for nitrogen fixation are not active; therefore, the legumes themselves become nitrogen starved. It should be noted that tall fescue, like forage legumes, performs best at optimum soil nutrient values. Maintaining good soil test levels should be the goal of all forage producers regardless of species grown.

Another misconception with forage legumes is that they actively share high amounts of nitrogen with their grass neighbors. Generally, grasses can only receive a minor amount of their nitrogen from neighboring legumes. This value is especially low during the legume establishment year or when soil/environmental conditions are poor for legume growth.

If you can establish and maintain legumes, the primary benefit arises from the legume itself providing forage nitrogen protein. Legumes can very rarely compete with grasses in terms of total biomass produced. Therefore, the trade-off is often “free” nitrogen in exchange for lower total forage yield. That trade-off can be positive or negative, depending upon environmental and field conditions present.

The bottom line is to manage tall fescue nitrogen based upon field specific environmental and production needs. In many cases, if you are short on hay or summer pasture this year, investing in May nitrogen will provide excellent economic returns.

Dr. Paul Tracy is director of agronomy for MFA Incorporated

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