| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 83 === The use of a boron-specific ion exchange resin Amberlite
IRA-743 for the extraction of available boron in soils was
investigated in this thesis. Five representative soils from the
major agricultural regions of Taiwan with four rates of boron
application, ie., 0, 0.5, 1, and 2 mg B kg-1, and incubated with
drying and wetting treatment, along with ten orchard soils were
used in this study. The results obtained were as follows:
.The resin had a very high affinity to boric acid or borate ion
in a wide range of solution pH, i.e., from pH 2 to pH 12. This
high affinity was not affected by the temperature, from 10 oC to
88 oC, and by the electrolytes or organic acids commonly occurred in soil solutions. The adsorption capacity of the resin calculated from Langmuir plot of adsorption isotherm was 0.85 mmole g-1 wetresin. 2.Boron adsorbed on the resin could be desorbed completely by continuous leaching the resin with a suitable aliquot of 1N solution. The resin capacity could be completely regenerated at least six times after in use in soil extraction by leaching with 1 N NH4OH solution. 3.The recovery of Boron added to soils , after seven cycles of drying and wetting treatment, were 45% to 70% and 60% to 85% by the resin method and hot water extraction method respectively. 4.The correlation between resin extractable boron and hot water soluble boron in a group of five soils with four rates of boron application was 0.937. The corresponding correlation between boron extracted by 0.05 M mannitol-0.01 M CaCl2 extractant was 0.977. 5.Boron concentration in citrus leaves was well correlated to the resin extractable soil boron and was poorly correlated to hot water soluble soil boron in this study. 6.The method, using twenty grams of soil shaken continuously with one gram of resin in 100 mL of water for 48 horus, was recommended as a routine procedure to assay soil available boron.
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