The availability of soil boron fractions to olive trees and barley and their relationships to soil properties

Soil boron occurring in various forms was correlated with boron contents in the leaves of olive trees in 51 and in barley leaves in 20 soils. The amounts of boron: in soil solution (CwsB), non specifically adsorbed (NsaB), specifically adsorbed (SaB), occluded in Mn oxides (MnoB), occluded in amorphous Fe-Al oxyhydroxides (FeoB), were correlated with soil properties such as: organic matter content, pH, free aluminum and iron oxyhydroxides (Ald, Fed), amorphous aluminum and iron oxyhydroxides (Alo, Feo). The later correlation studies were conducted on a total number of 153 soil samples inclusive of the soils used for the plant uptake investigations.The results show that the boron contents in the leaves of olive trees were significantly correlated with FeoB, CwsB, SaB and MnoB but with CwsB, NsaB, SaB and FeoB in barley leaves. The respective correlation coefficients suggest that available forms of soil boron vary with plant species.The hot water soluble boron was significantly correlated with all the fractions of boron studied except MnoB, confirming its value as a measure of available soil boron. However, the non significant (a=0.05) correlation with MnoB, which show significant correlation with the contents in the leaves of olive trees and barley, suggest that this procedure does not extract significant amounts of available B held in Mn oxyhydroxides.The highest amount of CwsB originated from the Cws B and to a lesser degree from the SaB and NsaB. The correlation among the boron held in the forms studied and the selected soil properties were either no significant or significant with the highest correlation found between FeoB and pH and Feo.