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Boron Toxicity

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Plant and Soil 193: 181–198, 1997. c 1997 Kluwer Academic Publishers. Printed in the Netherlands.

181

Chapter 12

Boron toxicity
Ross O. Nable1 , Gary S. Ba˜ uelos2 and Jeffrey G. Paull3 n 1

CSIRO Land and Water, P.M.B., P.O. Aitkenvale, QLD 4814, Australia , 2 Water Management Research Laboratory, USDA-ARS, 2021 S. Peach Av., CA 93727, USA and 3 Department of Plant Science, Waite Campus, University of Adelaide, Glen Osmond, SA 5064, Australia

Abstract Whilst of lesser prevalence than B deficient soils, B-rich soils are important, causing B toxicity in the field and decreased crop yields in different regions of the world. The highest naturally occurring concentrations of soil B are in soils derived from marine evaporites and marine argillaceous sediment. In addition, various anthropogenic sources of excess B may increase soil B to levels toxic for plants. The most important source is irrigation water, but others include wastes from surface mining, fly ash, and industrial chemicals. Ameliorating high-B soils is extremely difficult. A commonly used method of reclaiming high B soils is to extensively leach with low B water. Though used successfully, leaching may not be a permanent solution and causes difficulties with the disposal of the leachates. Other amelioration methods include the use of soil amendments (e.g. lime, gypsum) and the planting of plant genotypes that are tolerant of high external B concentrations. Although there are various methods available to determine the levels of B in soils, soil analysis can provide little more than a general risk assessment for B toxicity. Similarly, diagnosing B toxicity in plants, either by visible symptoms or tissue analysis has limited applicability. Thus at present, neither soil nor plant analysis can be recommended to precisely predict the growth of plants on high soil B. Recent physiological and genetic studies have provided some understanding of genetic variation in the response of plants to high...