Soil boron fractions and their relationship to soil properties

An understanding of soil nutrient pools and their relationship to soil prop erties and to soil test values should underpin soil tests, but few studies of this type have been conducted for soil B. Boron was fractionated by sequ ential extraction in 13 soils collected from north (47 degreesN) to south ( 20 degreesN) in eastern China. The nonspecifically adsorbed B (NSA-B) and s pecifically adsorbed B (SPA-B) comprised <1% of total B. By contrast, B occ luded in Mn oxyhydroxide (MOH-B), in amorphous Fe and Al oxides (AMO-B) and in crystalline Fe and Al oxides (CRO-B) comprised from 0.01 to 7.6% of tot al B. The content of the NSA-B fraction significantly decreased with increa sing mean annual rainfall of the site and increased with increasing soil pH and exchangeable Ca. The MOH-B fraction was positively correlated with soi l pH and cation-exchange capacity (CEC), and negatively with rainfall and t emperature. The AMO-B fraction was significantly related to amorphous Fe2O3 and rainfall. The CRO-B fraction was positively correlated with pH and exc hangeable Ca, but not with crystalline Fe2O3. The SPA-B fraction was not co rrelated with any soil properties or climate factors. These results emphasi ze that the forms of B in Chinese soils were distinctly different from thos e in soils of southeast USA and Greece.