BORON EXTRACTED WITH MANNITOL FROM IGNITED SOILS AND ITS RELATIONSHIPWITH THE DEVELOPMENT OF BORON DEFICIENCY OF PINUS-RADIATA GROWN IN POTS AND IN THE FIELD

A method is described in which boron is extracted from ignited soils w ith 0.05M mannitol and 0.01M calcium chloride. This method extracts si milar amounts of boron to the commonly used hot-water soluble method. Both methods are equally well related to the development of boron defi ciency and with boron taken up by Pinus radiata D. Don seedlings grown in pot trials but the mannitol method is better suited to routine ana lyses. Increased mannitol-extractable boron in surface soils was relat ed to increased growth and less boron deficiency symptom development b y P. radiata grown on yellow podzolic but not on yellow and red earth soils. In the yellow podzolic soils there was little extractable boron below the Al horizon. In contrast the distribution of boron in the pr ofile of earth soils was more uniform and thus the analysis of surface soils did not reflect the total amount of available boron.