Plant availability of boron doped on iron and manganese oxides and its effect on soil acidosis

The objective of this study was to test the availability of the boron from doped oxides to rape (Brassica napus L.), and the effect of the boron doped oxides on soil acidosis. The soil was treated with goethite, manganite and their boron-containing oxides including iron oxide with adsorbed boron (i.e. ad-B-goethite), iron oxide with occluded boron (i.e. oc-B-goethite), manganese oxide with adsorbed boron (i.e. ad-B-manganite) and manganese oxide with occluded boron (i.e. oc-B-manganite). It was found that the boron content of the soil treated with boron-containing oxides was higher than those in ordinary oxide treatments and in control. Rape seedlings grown on the soil treated with boron-containing oxides took up more boron than seedlings grown on ordinary oxide treatments and the control. There was a significant relationship between boron content in oxides, soil boron content and boron total uptake of the rape. The boron-containing oxides appeared to increase the plant available boron of the soil and therefore promoted boron uptake by the rape. This demonstrated that boron desorbed from oxides used in this study can be an important source of boron for plants in acidic soils. The two kinds of boron-containing oxides were found to be more effective in addressing soil acidosis by increasing soil pH and decreasing soil exchangeable acid than the oxide which was not doped boron. This was especially so for boron-containing manganite. The introduction of the oxides also enhanced soil available nutrient content and promoted rape seedling uptake of nutrients, and therefore promoted the rape growth. Regression analysis of nutrient content of the soil and rape seedling dry weight showed there was a significant positive correlation between the Ca and Mg content of the soil and rape seedling dry weight. Multiple regression results showed only Ca content in the soil significantly influenced rape seedling dry weight. It is surmised that the boron containing oxides provided a pre-condition for the absorption of nutrients, i.e., an environment for plants to better utilize Ca and other elements during seedling growth and therefore promoted rape seedling dry weight.