Smooth brome requires annual fertilization for optimum production. Fall is an ideal time to plan for fertilizing cool-season improved pasture perennial grasses, such as smooth brome. Particular attention must be paid to nitrogen, phosphorus, and pH. Information on fall soil testing of hayfields and pastures is discussed this week in a separate article by Alicia Boor, Agriculture Agent in the Cottonwood District, Great Bend office.
In this article I will address fertilization of smooth brome grass pasture and hayfields. Balanced fertility is essential. For example, adding nitrogen will not produce optimum yields if phosphorus is low. Soils low in phosphorus can limit plant and root growth. Fertilizer should be applied by broadcasting in the fall or before spring growth begins. This article discusses how nitrogen source, and application timing can affect forage quality and yield.
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 into ammonia gas, which is lost to the atmosphere (ammonia volatilization). This can occur fairly rapidly in the spring 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 (during cooler temperatures), volatilization losses should be minimal.
Application Timing -if brome is fall-grazed, 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 indicated by a soil test plus 20-30 pounds of nitrogen per acre. When applying any fertilizer, grazing can resume following the fertilizer prills/ pellets have dissolved to reduce livestock concerns. Before the soil freezes in November or December, apply the remaining nitrogen recommended for haying or grazing. Split or late fall applications generally initiate earlier green-up in the spring. To minimize loss, do not apply fertilizer to frozen soil.
Spring applications should be made as soon as the soil thaws and are acceptable for spring-only grazing or haying. 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, and P) - fertilizer rate recommendations ideally should be based on soil test values and yield goals for established stands of smooth bromegrass. When bromegrass is to be utilized for hay production, excessive N may cause lodging and reduce the amount of harvestable hay.
The Cottonwood Extension District has soil sampling hand probes that can be checked out with no charge from our offices in Hays and Great Bend. Before coming to get one it is best to call and make sure we have one available.
Stacy Campbell is a Crop Production Extension agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Extension. You can contact him by e-mail at scampbel@ksu.edu or by calling 785-628-9430.