AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Summer 2000, No. 8
FERTILIZE FOR QUALITY ALFALFA
Alfalfa varieties are now available for the Southeast that produce very well under different livestock grazing patterns such as continuous or rotational grazing. They can also be harvested for hay in the conventional manner. The following fertility and harvest management practices have proven effective for quality forage and long-term stand survival of dual purpose alfalfa varieties.
Stand establishment will benefit from a highly fertile soil. A firm, highly fertile seedbed helps to insure excellent seedling establishment. Lime and build-up fertilizer work best when incorporated into the topsoil prior to seeding. Targets include a pH level of 6.5 to 7.0 and phosphorus and potassium soil test levels in the high range. Other nutrient needs for the first year, such as sulfur, boron, magnesium and/or other micronutrients, can also be applied preplant. Well rooted plants lead to good stand health and longevity. Phosphorus promotes seedling root growth. Potassium and molybdenum do the same for nodule development. Cutting the first crop for hay at early bloom helps establish a healthy root system. Allowing animals to graze alfalfa plants no shorter than seven to eight inches anytime during the season helps maintain root reserves for improved regrowth.
Coordinate maintenance fertilization with spring grazing pressure and plant growth. Spring grazing should begin when plants are about six inches tall. Animal numbers can then be adjusted as plant growth rate changes during the season. This young alfalfa provides an excellent forage throughout the season with a protein level of 22 to 23 percent, digestibility of about 62 percent, and very high levels of nutrients such as potassium and phosphorus. Grazing animals recycle some nutrients, but in a non-uniform pattern. Manure droppings kill a few plants, feed a few and contain nutrients positionally unavailable to many. Thus, plants between manure piles can become nutrient starved and have maintenance fertilizer needs similar to those from harvested hay fields.
Alfalfa has a big appetite, especially for potassium. For each ton of quality alfalfa hay removed from the field, about 15 pounds of phosphate and 60 pounds of potash are removed and need to be returned in the maintenance fertilizer.
Boron and sulfur are key to quality forage. Rates, in general, range from 2 to 3 pounds of boron and about 30 pounds of sulfur per acre per year. Both sulfur and potassium interact with nitrogen for optimum protein production. Boron encourages new tissue development in both roots and shoots.
Time maintenance fertilizer applications with plant growth need. Consider splitting the phosphorus, potassium, boron, and sulfur requirements into late spring and early fall applications. Broadcast after the first harvest for hay or first month of grazing to allow the plants to benefit from nutrients released during winter. The second application is timed following the next to last hay harvest in the fall or about a month prior to the first expected early winter freeze. This not only promotes increased fall production and forage quality but increases plant root reserves needed for greater tolerance to winter temperature stress and for faster spring regrowth rate.
Hay it or graze it for top alfalfa yield and quality. A summary of 58 location years of university testing across the country showed that alfagraze yielded 5.77 tons per acre while hay-type alfalfa yielded 5.65 tons per acre. Other studies revealed dual purpose alfalfa to have greater grazing survival, a higher average percent leafiness (63.6 vs 61.5 percent) and improved winterhardiness over hay-type varieties.
For more information, contact Dr. Noble R. Usherwood, Southeast Director, PPI, 233 Kenilworth Circle, Stone Mountain, GA 30083. Phone: (404) 294-0137. E-mail: email@example.com.
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