Cool-season forages require annual fertilization for optimum production. Fall is a good time to plan on fertilizing cool-season improved pasture or hayfields of perennial grasses such as smooth brome. Particular attention must be paid to nitrogen, phosphorus, potassium, and pH. Ideally a soil sample should be taken before-hand to know how much of each nutrient you need. If you need information on how to take correct soil samples for brome grass contact your local Extension Office. We have soil probes you can check out to do it as well.
Balanced fertility is essential. For example, adding nitrogen will not produce optimum yields if phosphorus is low. Soils low in phosphate limit plant and root growth. Fertilizer should be applied by broadcasting in the fall or before spring growth begins.
• Nitrogen Source - nitrogen management is critical for optimum smooth brome production. Several nitrogen sources are available — liquid nitrogen solutions, urea, ammonium nitrate, and anhydrous ammonia. Anhydrous ammonia is not extensively used on permanent pastures because application is difficult. Nitrogen source research generally has shown little difference among sources under most conditions. When urea fertilizers — including liquid nitrogen — are applied to moist soils covered with grass residue, an enzyme called urease can break down the urea to ammonia, which is lost to the air. This can occur fairly rapidly when moist conditions are followed by warm temperatures, and rapid drying occurs without rain to move the urea into the soil. If urea is applied from November through February, volatilization loss should be minimal.
• Application Timing - when brome is grazed or hayed in the fall, the yearly nitrogen application should be split. If adequate soil moisture is available for good growth in late August and early September, apply all phosphorus and potassium indicated by a soil test plus half of the nitrogen recommended per acre. Then before the soil freezes in November or December, apply the remainder of the nitrogen recommended for haying or grazing. Split or late fall applications generally initiate earlier green-up in the spring.
If soil moisture is limited, apply all nitrogen, phosphorus, and potassium before the soil freezes in November or December. To minimize loss, do not apply fertilizer to frozen soil.
Spring applications should be made as soon as the soil thaws are acceptable for spring-only grazing or haying. Timely application can be delayed because of wet soils. An application needs to be applied in the fall or early spring to allow sufficient time for fertilizer incorporation to benefit forage production.
Fertilizer Rates (N, P, and K). Due to space limitations for this article, Fertilizer rate recommendations for N, P, and K for established stands of smooth brome grass can be accessed by going to https://eupdate.agronomy.ksu.edu and looking at the Oct. 10th issue of the K-StateAgronomy eUpdate.
Stacy Campbell is an Agriculture and Natural Resources agent for Cottonwood Extension District. Email him at scampbel@ksu.edu or call the Hays office, 785-628-9430.
