Boron deficiency and toxicity symptoms for several crops as related to tissue boron levels

Boron deficiency symptoms in snap beans (Phaseolus vulgaris L.) showed as general yellowing of tops with slow flowering and pod formation, while toxicity caused reduced growth and burned dark brown older leaves especially on the edges. In radish (Raphanus sativus L.)f B deficiency resulted in roots which were brown upon cutting and had thick periderm. Even at 4 ppm applied B, no visible B toxicity was noted in radish. The plant tissue B levels of less than 9 to 12 ppm were associated with B deficiency in radish and beans; and greater than 125 ppm with B toxicity in beans. In tomatoes (Lycopersicon esculentum, Mill) B deficiency resulted in reduced growth while B toxicity at 4 ppm applied B caused poor and slow germination. Boron deficiency and toxlcity in tomatoes were related to < 12 and > 172 ppm B, respectively, in tissue. No B deficiency was noted in corn (Zea mays L.) and timothy (Phleum pratense L.). The B toxicity in these two crops appeared as marginal burning and dark brown tips of older leaves and was related to greater than 98 and 176 ppm tissue B in corn and timothy, respectively.