Boost Forage Fertility

Planning Vital for Forage Fertility Management

Strategic planning by means of soil testing, following recommendations and having forage yield goals are vital in forage fertility management, according to A.J. Foster, southwest area agronomist for Kansas State University Extension in Garden City, Kansas. (DTN/The Progressive Farmer file photo)

OMAHA (DTN) -- Keep calm and have a plan. That's the advice a Kansas State University Extension agronomist has for producers trying to manage their forage fertility.

Forage fertility management should not be something you make up as you go. Strategic planning by means of soil testing, following recommendations and having forage yield goals are vital in forage fertility management, according to A.J. Foster, southwest area agronomist for Kansas State University Extension in Garden City, Kansas.

Soil testing is crucial for managing fertility in pastures and alfalfa fields, Foster said.

"If you're not soil testing, you're guessing," Foster said. "The only way you're going to know the amount of nutrients in your soil and the amount you need to apply is to have a soil test."

The danger of not soil testing is that farmers are either lacking the necessary nutrients needed for forage to grow, which could decrease yields, or they are applying too much, which is a waste of money.

Foster said for new ground just acquired or land that farmers don't have much previous information on, he recommends testing every two years for 10 years, then every four to five years after that.

"With the first 10-years span, you will have about five data points, then you will have two data points every 10 years after that," he said.

For soil tests for pastureland, farmers will mostly focus on soil organic matter and pH levels, as well as phosphorus and potassium. Nitrogen, however, is a little different.

"The amount of nitrogen you put on is often based on your yield goal, especially with a hay system," he said. "You want to fertilize based on the tonnage you desire or how many grazing days you desire for your cows on a pasture. However, in some areas, soil test nitrogen and organic matter are also important and often provide some nitrogen credit when determining the amount of nitrogen needed to achieve the yield goal."

Foster added that pasture systems have an advantage of needing less nitrogen because of the recycling of nutrients through the cows' manure and urine. The challenge is how those nutrients are distributed in that pasture.

"The nutrients follow the animals," he said. "If you have all your cows congregated in one spot, that's where the nutrients will be."

Foster recommended setting up pasture systems in such a way that nutrients are distributed more evenly, such as rotating the location of hay, additional feed, minerals, water or shade in the pasture.

"Try to get more movement; get the cows to walk around," he said. "Then you will get better distribution of manure across the field.


When filling out information for soil tests, Foster said it is vital to fill in a yield goal on the sheet.

"Your recommendations from the soil test will be tied to that yield goal," he said.

Foster said most sheets will have four yield goal slots per sample, so he recommends utilizing all four and listing four yield goals in order to compare recommendations.

But the yield goals have to be realistic. He said a good place to start for your yield goal if you don't already know your farm yield average is your county average. For the four yield goal slots, he recommends asking for recommendations for:

-- Slightly below the county average.

-- The county average.

-- Slightly above the county average.

-- Even higher than the county average.

Having different recommendations helps with planning, he said. For instance, if a producer's area is dry, you may want to go with the lower yield goal.


Foster said after doing a soil test and following the recommendations, it is important for producers to have a plan of how they are going to utilize the additional forage they will get from that fertilization, especially for pastures.

"If you don't have the animals to graze the pasture or have plans to cut it for hay, then you don't want to invest," he said. "We always say for forage: If you're going to fertilize, you have to be able to utilize."

He stressed that forage is perishable and loses quality while in storage.

"Forage is not going to retain its quality if you keep piling and piling it in storage," he said. "That bale of hay is going to degrade over time, so you want to make sure when you invest in fertilizer, you get a good return on your investment."

Foster said that farmers can call an Extension office or the Natural Resources Conservation Service to help estimate the amount of forage they have or will need, so they can determine how many days they can put their cattle on a pasture, how much feed is actually out there, and how many cattle they can put on a specific field.

Since cattle consume about 2%-3% of their bodyweight per day, and assuming they are about 70% efficient, a 1,000-pound cow will need about 30 pounds of forage per day. That can help producers estimate how much forage they will need.

Foster added that for each type of forage, both the NRCS and Extension offices have guide sheets that provide methods for estimating how many tons of forage are available in a field base on per inch of plant height and/or plant density.


Nitrogen application for cool-season grass for hay can be done in late winter or early spring to get a big benefit for the spring growth. Or it can be put on after the first cutting to promote further growth. Foster said with hay, farmers could even put on some nitrogen after each cutting to stimulate new growth for the next cutting.

For pasture, it depends on your need and ability to utilize the additional forage. Do not fertilize mixed grass/legume pasture with nitrogen.

Cool-season grasses like tall fescue will begin growing early in the spring, so Foster recommended putting fertilizer on in early spring to get good spring growth, but only if you have a need for the additional forage.

Farmers will want to put nitrogen on warm-season grasses that come on later in the spring, probably around April-May when it first starts warming up and the plants begin to grow. However, with warm-season grasses like Bermuda grass, farmers may also consider putting nitrogen on after each cutting. Foster said not to fertilize with nitrogen if conditions are not favorable (most often dry) for good response and if you don't have a plan for utilizing the additional forage.