Farm Talk

March 6, 2013

K-State: time to think about fertilizing pastures

by Keith Martin

Parsons, Kansas — Much of the nitrogen (N) applied to tall fescue and smooth bromegrass hay meadows and pastures may have already been applied in our area. However, there is still time to make a fertilizer application if needed before the cool season grasses come out of winter dormancy. Determining whether to apply fertilizer and if so, how much depends on many factors. These would include: whether the field is hayed or grazed; how much, if any N was applied in the fall; the price of fertilizer,  the value of hay or forage produced; and the growing conditions since last fall.


Normal N fertilization rates for established fescue and bromegrass hay fields are 50 to 100 pounds actual N per acre, or about 30 pounds of N per ton of expected yield. A recent summary of fescue and bromegrass N response data shows that across nearly 100 experiments, the average yields for unfertilized plots was 1.35 tons of hay per acre, while maximum yields averaged 3.15 tons of hay with 140 pounds of N.

Doing some simple cost-and-return calculations, using a long-term average value of $60 per ton as the value of the hay produced and $0.50 per pound of N, the normal rates of N mentioned above (90 to 120 lbs/acre) are appropriate to maximize profit in most years. It will be important to watch N costs, however, as they continue to be volatile.

The other issue is hay price and supply. With the drought, prices for grass hay have been considerably above the long-term average of $60 per ton. With the reduced hay supplies on many farms and current lack of soil moisture in many parts of the state, there is a good chance hay prices may continue to remain high in 2013. If that is the case, applying N rates at the upper end of the 90 to 120 pound range should be most profitable.

One issue these calculations don’t consider is hay quality. There is potential for harvesting hay with a higher protein level as long as the hay is harvested in the boot stage.  Of course that advantage is diminished or goes away if grass is allowed to mature when grazed or harvested for hay. In that case extra fertilizer just results in more low quality hay. Hay harvested in the boot stage has the potential to meet all of the protein and energy needs of beef cows in all stages of production. A forage test available through our office provide will provide insight into the true value of the hay you produce or purchase.


Under normal conditions, tall fescue and smooth bromegrass pastures that are grazed in both spring and fall should receive about 100 pounds total N per acre, with 60 percent applied in the winter or early spring and 40 percent in late August or early September, along with any needed P and K. So producers should plan on applying 60 to 70 lbs N per acre in winter or early spring.

To get a good response from nitrogen applications, phosphorous and or potassium must be applied if needed. Best results from phosphorus and potash applications occur when they are applied prior to the forage coming out of summer dormancy along with a small amount of nitrogen.  Early fall applied Phosphorus will help the grass develop a good root system for the winter, and develop buds for new tillers the next spring. P and K applied in winter or early spring won’t provide the same benefits. If no phosphorus or potassium was applied last fall, it can be applied along with the early spring application of nitrogen.

Other considerations

One additional nutrient producers should consider watching for tall fescue and smooth bromegrass pastures or hayfields is sulfur (S). The only way to determine if sulfur along with phosphorous, potassium or lime are needed is through soil testing. Contact your local extension office for the procedures needed to submit a soil sample for analysis. An ideal time to sample is 30 days prior to fertilizer application. Samples for a P and K soil test should be taken to a 6-inch depth. A profile N test to a depth of 24 inches should be used to evaluate S needs.

For information about this and other livestock and forage topics contact the K-State Research & Extension, Wildcat District office at 620-784-5337 or email me at £

   N Rate                  Hay Yield                    Hay Yield Increase

(lbs N/acre)   (tons dry matter/acre)    From 20 lbs. N (tons

                                                                        dry matter/acre)

                      0                        1.35                             -------

                     20                        1.80                             0.45

                     40                        2.20                             0.40

                     60                        2.52                             0.32

                     80                        2.78                             0.26

                    100                       2.97                             0.19

                    120                       3.10                             0.13

                    140                       3.15                            0.05

                    160                       3.14                           -0.01

(Source Dr. Dave Mengel, KSU Extension Soil Fertility Specialist)