Alfalfa Requires Careful Nutrient Management For Maximum Benefit

FAYETTEVILLE, ARK.
   Alfalfa makes a quality forage or hay crop, but its growth habits require careful nutrient management, said Dirk Philipp, forage researcher for the University of Arkansas System Division of Agriculture.
   Alfalfa removes nutrients from the soil at a high rate and is sensitive to nutrient deficiencies, Philipp said. “It will quickly reduce yields and persistence if soil fertility is not kept at optimum levels,” he said.
   The issue is not nitrogen, Philipp said. Alfalfa is a legume that fixes the nitrogen it needs through a symbiotic relationship with bacteria in the soil.
   The key nutrients that require management are phosphorus, potassium and calcium, Philipp said. Inadequate phosphorus and potassium, in particular, can lead to plant deficiencies that will be costly to correct.
    emphasizes the importance of keeping current on soil tests. “Make a habit out of testing soil every one to two years,” he said. The Division of Agriculture offers free soil tests.
    “Springtime is crucial for keeping up with soil fertility demands in crops like alfalfa,” Philipp said. “Growth rates are high in spring and soil fertility is usually a low priority during winter.”
   Philipp recommended:
   Removal rates should be calculated when the forage or hay is removed. A ton of alfalfa dry matter removes about 50 pounds of actual potassium and about 6 pounds of actual phosphorus. A ton of dry alfalfa also removes about 30 pounds of calcium.
   Apply phosphorus and potassium immediately after the first cut. Split the application if the amount needed is really large.”
   Be smart in purchasing fertilizer; calculate the actual cost of the mineral per unit of fertilizer.
   Minimize passes across the field by purchasing fertilizer that replaces as many of the needed minerals as possible.
   Soil pH are also critical, Philipp said. Nutrients are most available to alfalfa when soil pH is between 5.5 and 7.5, he said. The availability of soil nutrients may be greatly reduced when pH is above or below that range.
   If soil tests call for lime, make applications in the fall because it takes six to eight months to change soil pH, Philipp said. If pH is very low, lime application can be made in the spring.
   “And keep up with soil test reports,” Philipp said. “This cannot be said enough.”
   Free Division of Agriculture soil tests can be arranged by contacting the local County Extension Office. ∆