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Topics : Soil Fertility for Forage Crops : Maintenance


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Boron and Forages

Alfalfa has a high boron requirement and grasses have a low boron requirement. Other legumes are somewhere in between in their boron requirement. Alfalfa will remove about 0.05 pounds of boron per ton of hay equivalent. A soil test recommendation for boron greater than 1 ppm is considered adequate for alfalfa and greater than 0.5 is considered adequate for the other forage crops. The sufficiency level for plant analysis for boron in the top one-third of the alfalfa plant, sampled between bud and one-tenth bloom stage is 30 ppm (Table 5). This can be compared to the sufficiency level for clover which is 20 ppm boron in the tissue and the grasses which require 5 to 10 ppm in the tissue. The common symptom of boron deficiency in alfalfa is "alfalfa yellows," or stunted yellow alfalfa plants. This is usually associated with drought conditions. A routine recommendation in Pennsylvania is 2 pounds of boron applied when alfalfa is topdressed with fertilizer. If a serious boron deficiency is suspected, based on soil tests or plant analysis, the rate may be increased up to 4 pounds of boron per acre. Because corn is somewhat sensitive to boron toxicity, do not apply excessive boron on fields that will be rotated to corn