As the weather turns cooler, cool-season grass pastures enter their most productive period of the year. For optimum production, producers need to apply sufficient fertilizer to these grasses at the right time of year, says Dale Leikam, Kansas State University (KSU) Extension nutrient management specialist.

"Nitrogen (N), phosphorus (P), potassium (K) and sulfur are the nutrients which most commonly limit cool-season grass production in Kansas," he says.

If cool-season grass pastures have not been sampled yet for soil-test analysis, the KSU agronomist says, it should be done at once. "Cool-season grasses may need more than just N. Balanced fertility is essential to optimum yield and high quality hay. For example, adding N won't produce optimum yields if the soil P or K levels are low," Leikam says.

While the November-February time frame is optimum for most fertilizer applications to many cool-season grass pastures, Leikam says there are situations where it might be best to split applications between an August-September application and a November-February application. The conditions in which a split application might be preferred include:

  • If the cool-season grass is to be grazed/harvested in both the fall and spring;
  • If the cool-season grass stand has been subjected to drought or overgrazing stress;
  • If the field is to be used for seed production.
Don't apply nitrogen fertilizers to frozen soils, since there's a real potential of N washing off the field in runoff, Leikam adds.

"Over the years, large amounts of P and K are removed from cool-season grass pastures, and P and K soil-test values are often low. Cool-season grasses are relatively responsive to applied P and K if soil tests are low," the scientist explains.

If the N, P and K needs of the crop are completely satisfied, sulfur would be the most likely nutrient to limit cool-season grass production. A rate of 10-15 lbs. of sulfur is the suggested rate of application, he says.

Finally, soil pH is sometimes a consideration for cool-season grass pastures, Leikam adds. "Both forage production and stand longevity are reduced when the soil pH is less than 5.5. At higher soil pH levels, however, cool-season grass responses to lime have been inconsistent in KSU tests. If lime is to be applied, surface-apply no more than 2,000 lbs. effective calcium carbonate (ECC) per acre at one time, Leikam says.

More info on smooth bromegrass management is available at: www.oznet.ksu.edu/library/crpsl2/c402.pdf.
-- KSU news release