June 2018 Articles

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Potassium Important for Bermudagrass Stand Persistence

Potassium Important for Bermudagrass Stand Persistence — Bermudagrass is an important summer perennial for both grazing and hay production, and has been a part of southern agriculture for at least the last century. Its characteristics include high yielding potential, drought resistance, and a degree of soil acidity tolerance. We rely heavily on our bermudagrass pastures and hay meadows during the summer in most parts of Louisiana. However, hybrid bermudagrass fields that were once highly productive have gradually declined in many areas. Annual forage yield reductions have been attributed to weed competition, stand loss as a result of diseases or winter-kill, and/or a continued neglect of sound fertilization practices. This is often times referred to as “Bermudagrass Decline”. To achieve good yields and good quality, the forage producer needs to pay close attention to the plant nutrient requirements, forage maturity, and nutrient removal. Table 1 shows nutrient uptake at three yield levels of bermudagrass. Research conducted at the Hill Farm Research Experiment Station has shown that for every 2.0 tons/A of hay yield goal per cutting, the following nutrients must be provided….from soil and/or fertilizer
A livestock producer should be aware that, when forage growth is removed as hay, virtually all nutrients in the above-ground portions of the plants are removed. Potassium (K2O or “K”) is needed by plants in relatively large amounts. This nutrient should be present in adequate amounts at all times. It has been shown to be important in reducing the susceptibility of bermudagrass to leafspot diseases, as well as winterkill, and for enhancing root growth and development. A deficiency in K will result in poor stress tolerance, reduced winter hardiness, decreased disease resistance, and reduced rhizome and stolon production. To determine if K deficiency is causing the problem, a soil analysis will be imperative. Because of its durability, bermudagrass has long been a favorite pasture forage and hayfield grass in the southern United States. It thrives under warm, humid conditions, has relatively few pests, withstands heavy grazing pressure and tolerates weather extremes often experienced in our region. While bermudagrass is commonly considered a hardy forage, it cannot tolerate low soil fertility over long periods of time. To cut costs, many cattlemen often apply ample amounts of nitrogen but fail to maintain proper soil pH and adequate soil levels of potassium. Applying adequate amounts of potassium to bermudagrass hayfields is of utmost importance because of large amounts removed with each harvest. Economic competitiveness and a desire for improved environmental stewardship demand that we do everything possible to maximize the efficient use of applied nutrients, regardless of source (fertilizer or manure). One way to accomplish these goals is to provide balanced plant nutrition. Research at the Hill Farm Research Station has shown that 400 lb of N/A/year produced the maximum economic yield of Coastal bermudagrass hay. At this same N rate, the uptake and N-use efficiency were maximized with 400 lb of K2O/A. Annual applications of at least 400 lb of K2O/A were required to rejuvenate thinning bermudagrass stands. The results of decades of research at the Hill Farm Research Station indicate that 100 lb/N, 30 lb/P, 120 lb/K, and 25 lb/S applied per acre per cutting of hay appears optimal for bermudagrass hay. An ideal N-P2O5 -K2O - S ratio in fertilizers for bermudagrass would be 4:1:4:1. For any crop production system to function at optimal efficiency, a complete and balanced fertility program is essential. Now is a good time to make sure your forage crops are not going into the summer months short of needed nutrients. — Jason E. Holmes, LSU AgCenter