UNIVERSITY of Illinois assistant professor of crop sciences Fabian Fernandez has noticed visible signs of boron deficiency in alfalfa. In Illinois, alfalfa is the crop most sensitive to boron deficiency. Corn and soybeans have very low boron requirements, and boron toxicity can be a problem for corn if large amounts of the nutrient were applied to an alfalfa stand in the year prior to planting the corn. Fernandez says boron deficiency in alfalfa is most common in sandy soils that are low in organic matter or in soils with a high pH. Often, boron deficiency appears during drought conditions because the lack of water reduces the capacity of organic matter to release the nutrient. "Boron does not translocate easily in theplant," explains Fernandez. Asa result, signs of the deficiency are yellow-reddish leaves in the top portion (new growth) of the alfalfa plant, while the older leaves remain green. For this reason, the deficiency is often referred to as "yellow top."
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