AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Summer 2002, No. 6
MAKE BALANCED BERMUDAGRASS FERTILITY A PRIORITY THIS SUMMER
Bermudagrass is an important warm season forage grass in the southern U.S. It has high yield potential, drought resistance, and tolerates relatively acidic soil conditions. It can be produced for grazing, hay, or a combination of both. Hybrid bermudagrass is generally more aggressive and productive than common bermudagrass.
Fertility is one of the most important factors affecting the yield, nutritive value, and stand longevity of bermudagrass. High yield hay production can result in the removal of large quantities of nutrients from soils. The results of inadequate fertility inputs include nutrient depleted soils, diminished yields, thin stands, and lost profits.
Bermudagrass takes up almost 50 pounds of nitrogen per ton of hay harvested. Proper nitrogen fertilization is associated with improved shoot and root growth, stress tolerance, resiliency, and protein content. Nitrogen levels in bermudagrass tissue should be maintained at 2.2 percent of the dry matter or higher to obtain optimum yields. Common hay meadow recommendations call for the application of 100 pounds nitrogen per acre at initial green-up in the spring, followed by similar rates after each harvest except the final one. Proper balance of nitrogen with phosphorus, potassium, and other nutrients is important in maximizing nitrogen use efficiency.
As much as 100 pounds of P2O5 per acre will be taken-up in the production of top bermudagrass yields. For each ton of hay produced, about 12 pounds of P2O5 are removed. In a rapidly growing, high-yielding crop, P2O5 uptake can equal 1.2 pounds per acre per day. Sufficient phosphorus fertility is commonly associated with increased root growth and branching, increased nitrogen use efficiency, and improved drought tolerance and recovery.
Approximately 50 pounds of K2O are required for every ton of bermudagrass produced. Uptake of potassium can be more than 4 pounds K2O per acre per day in a rapidly growing crop. Without proper fertilization, reserves of soil potassium can be rapidly reduced under intensive bermudagrass hay production. One east Texas study showed a 69 percent reduction in soil test potassium with a corresponding 37 percent reduction in yield after three years of hybrid bermudagrass hay production without potassium fertilization. Adequate potassium fertility is important in bermudagrass rhizome production, stand density, and longevity. In another east Texas study, rhizome production measured after three years of potassium applications was increased by about 14-fold over the zero potassium control. This, in turn, resulted in much greater stand density compared to the no potassium treatment. The maintenance of adequate potassium levels through the summer months up to the onset of dormancy is important in the manufacture of carbohydrates for root growth and carbohydrate storage. Potassium also improves water and nitrogen use efficiency and helps maintain good stand density. In addition, adequate potassium fertility is associated with increased disease resistance and improved winter hardiness.
The secondary nutrients should not be neglected in bermudagrass production. High yields may require more than 20 pounds of magnesium and 40 pounds of sulfur per acre. Micronutrient fertilization may also be necessary in intensive, high yielding production. Liming is important in acid soil environments. Sufficient lime should be applied to maintain soil pH at 5.6 or higher.
When planning bermudagrass fertility programs this summer,use soil tests and consider yield and nutrient removal levels.Also consider plant analysis where appropriate. Complete and balanced fertility ensures optimum bermudagrass yield, quality, stand longevity, and maximum profit.
For more information, contact Dr. W.M. (Mike) Stewart, Great Plains Director, PPI, P.O. Box 6827, Lubbock, TX 79493. Phone: (806) 795-3252. E-mail: firstname.lastname@example.org
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