PLANT AND SOIL BORON AS INFLUENCED BY SOIL pH AND CALCIUM SOURCES ON PODZOL SOILS

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Abstract
Studies conducted on three podzol soils with original pH values of 5.0 to 5.4 showed that the sharpest decrease in boron concentration (from 117 to 388 down to 58 to 83 ppm) in barley (Hordeum vulgare L.) and pea (Pisum sativum L.) plant tissues occurred with addition of 2.5 g lime/kg soil. Such rates of lime resulted in soil pH values of 6.8 to 7.3. Additions of 5 g lime/kg soil resulted in soil pH values of 7.3 to 7.7 and further tissue B level decreases of lesser magnitude than the 2.5 g lime rate. A fourfold increase to 20 g lime did not result in further decreases in tissue B. At equivalent amounts of calcium, tissue B concentrations were much higher using CaSO4 rather than CaCO3. Plant tissue B was related to soil pH rather than to the amount of Ca. Chloride used as a source of Ca resulted in poor to no growth of crops. The greatest decreases in hot-water-soluble (hws) B occurred with 10 g lime/kg soil. Beyond this rate, no further decreases in hws B occurred. Liming induced B deficiency in peas. Tissue B levels of 8 ppm in peas were associated with B deficiency, and levels of greater than 61 ppm were associated with B toxicity symptoms on the foliage.
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