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Fluid Journal : Fluid Journal 1996-1998
1 Fluid Journal Fall 1996 Summary: Numerous experiments have shown that applications of NPK, plus secondary nutrients can significantly enhance yields and quality of bermudagrass on southern dairy pastures. Ag scientists have found that the warm, high rainfall climate of this geographic region of the United States is conducive to acid soils and low soil fertility. Thus the abundant opportunities to apply sound fertilization practices that produce efficient, profitable production. Perennial warm season forages are grown on 50 to 60 million acres of cropland in the South. There are approximately 15 million acres of Coastal bermudagrass, about 2 million acres in Texas alone. Hybrid bermudagrasses are high-yielding forages with acceptable quality, if managed properly, for both beef and dairy animals. Because dairy animals are especially sensitive to fluctuations in forage quality, an agronomically sound fertilization program is essential for bermudagrass production. The two most important factors affecting forage quality are fertility and age of the bermudagrass at harvest. Soil tests and a knowledge of crop nutrient requirements for targeted yield goals are two first steps in determining fertilizers needed for optimum bermudagrass production and highest profits. An important axiom to remember is "a fertile soil is not always productive, but a productive soil is always fertile." Figure 1 dramatically shows what a big appetite Coastal bermudagrass has for nitrogen (N) and potassium (K). Large applications of these nutrients are required if forage yield levels and quality are to be maintained. Adequate amounts of sulfur (5), calcium, magnesium (Mg) and micronutrients are also required to assure optimum forage yield and quality. We'll briefly review the more important inputs. Nitrogen Nitrogen stimulates plant growth and increases crude protein content of forage. With adequate moisture, bermudagrass will respond to high rates of nitrogen. Studies have shown that several applications of N prove more efficient than a single large application. The quantity of N and frequency of application will depend on how the crop is used---for grazing or hay---and how intensively it is managed. As bermudagrass management improves and yields increase, crop demands for and responses to nitrogen fertilization increase. Figure 2 shows that under good management, yield response of bermudagrass to 400 lbs/A or more of N per year is dramatic. Nitrogen also has a similar effect on forage quality and water-use efficiency as shown in Figure 3. Nitrogen applications have to be specific to crop need and growth stage in order to get the best use efficiency from the applied N. Phosphorus/potassium While nitrogen alone is effective in improving the yield and quality of bermudagrass, it is even more effective in combination with phosphorus and potassium. Phosphorus is essential for early vigorous root and shoot growth. It promotes early growth, especially when soils are cool. It helps resist winterkill and overcome drought stress. High forage P content improves forage quality and animal performance. It is vital to seedling establishment, crop by Drs. B.C. Darst, J.N. Pratt, H.D. Pennington, W.B. Gass Nutrient Demand High In Bermudagrass Studies show yield benefits of proper fertilization on southern dairy pastures. persistence and longevity. Potassium promotes N-use efficiency, root growth, cold and drought tolerance, stand longevity and density, protein formation, and forage digestibility. Sulfur Research in the South is showing greater need for sulfur. One study showed S applied with N increased yields of Coastal bermudagrass up to a ton per acre. Arkansas research has shown it improved N recovery as much as 72 percent, as well as palatability, digestibility, and intake. N Nutrient PO 25 KO 2SMg 10 50 90 130 170 210 250 290 Update - lbs/A Figure 1. A 6-ton yield of Coastal bermudagrass takes up large quantities of nutri- ents, especially N and K; PPI Plant Food Uptake (PFU) Folder for Southern Crops.
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