| Different forms of boron-containing goethite and manganite were synthesized artificially. Through introducing them to the acid yellow-brown soil, the plant availability of the boron contained in the oxides and the effect of the boron-containing oxides on soil proprieties were observed, and the main results were shown as follows:1. The synthesis method of goethite, manganite and their boron-containing oxides were described and the properties of the oxides including surface areas, SEM photos and boron content of the oxides were discussed. The results showed that the changes of the specific surface area exhibited the same trends, that is oxide with occluded boron> ordinary oxide> oxide with adsorbed boron. And scanning electron microscopy results showed that the particles of goethite with occluded boron (i.e. oc-B-goethite) were more fine than ordinary goethite and goethite with adsorbed boron (i.e. ad-B-goethite), which is related to the combination form of boron on oxides.The boron content of the boron-containing oxides were extracted by different methods, it was found that the boron content of the goethite and manganite was greatly different, the boron content of boron-containing goethite is much higher than that of boron-containing manganite. And the boron content between oxides with adsorbed boron and oxides with occlude boron was also different, the boron content of ad-B-goethite was much higher than that of oc-B-goethtie, but the difference between manganite with adsorbed boron (i.e. ad-B-manganite) and manganite with occluded boron (i.e. oc-B-manganite) was relatively smaller.2. The effect of different amounts of the oxides on soil boron content, soil acidity, boron content of rape and rape biomass were investigated. The results showed that with the increasing of the boron-containing goethtie added into the soil, the boron content of the soil and rape was also increased. And when the amount of the boron-containing goethtie reached to 5 or 10 g kg-1 soil, the boron content of the soil and rape showed a dramatic rise phenomenon. But with the increasing of ordinary goethite added into the soil, the boron content of the soil and rape was reduced. The boron-containing manganite also increased the boron content of the soil and rape with the amount increasing.With the addition of boron-containing oxides increasing, the biomasses of rape showed a growing trend. When the amount of the oxides reached 3 g kg-1 soil, the biomasses of the rape reached maximum.The improvement of the soil acidity by the boron-containing iron and manganese oxides showed a clear dose relationship. The boron-containing iron oxides presented a stable increase on improving soil acidity with the amount increasing of the boron-containing goethtie, but it appeared a turning point of 2 g kg-1 soil addition of boron-containing manganite.Based on the above phenomenon, we think when the additive quantity of the oxides was 2-3 g kg-1 soil; it will be the best dose for our further research.3. Through the addition the boron-containing iron and manganese oxides into the soil, the influence of the boron-containing oxides on soil boron fractionation and the uptake of boron by rape was observed in a pot experiment. The results showed that the addition of the boron-containing oxides into the soil increased different forms of boron content including water soluble boron, nonspecifically adsorbed boron, specifically adsorbed boron and boron occluded in Fe and Al oxides. And the effect of boron-containing goethite on increasing soil boron content was greater than that of boron-containing manganite. The introduction of the boron-containing oxides was also increased the boron content of the shoot and root of rape.The simple linear regression analysis between different forms of the soil boron content and boron content of rape was calculated, results showed that the content of water soluble boron, nonspecifically adsorbed boron, specifically adsorbed boron and the boron occluded in amorphous Fe and Al oxides in the soil was all significantly correlated with the boron content of the shoot and root of rape. However, stepwise regression showed that only the water soluble boron and boron occluded in amorphous Fe and Al oxides in the soil was significantly correlated with the boron content of rape, which indicated that not only hot water-soluble boron can be regarded as a suitable index of plant available boron, the boron occluded in amorphous Fe and Al oxides also can play an important role in promoting the boron uptake by plants.4. 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.5. Rhizobox experiment was conducted to investigate the impact of boron-containing oxides on rhizosphere soil proprieties. The exchangeable acid and exchangeable Ca and exchangeable Mg all showed a positive rhizosphere effect; whereas the soil pH and exchangeable K in the rhizosphere soil was lower than that in the bulk soil. The addition of boron-containing oxides also stimulated soil enzyme activities, of which the catalase and polyphenol oxidase activity in rhizosphere soil was greater than that in the bulk soil, but the invertase and acid phosphatase activity in rhizosphere was lower than that in bulk soi.Rape seedling root morphology were analyzed using a WinRHIZO 2.0 Scanner Instrument, it showed that the rape roots growning on the boron-containing oxides treatments were more developed by increasing the total root length, root area, root tips, root volume and root surface area.6. A pot experiment was conducted to investigate the impact of boron-containing oxides on rape physiological proprieties. Results showed that the boron-containing improved the physiological adaptability of rape. Compared with the control, they all raised the chlorophyll and soluble sugar content of the leaves, as well as the root activity of rape. Also the addition of boron-containing oxides reduced malondialdehyde and proline accumulation in the leaves of rape.7. The release mechanism of the boron from the boron-containing oxides was investigated by loading the oxides onto quartz sand. Sand culture experiment was undertaken to investigate the release of the boron from the oxides clearly. It was found that the iron oxide in the quartz sand surface is not uniformly distributed, it mainly concentrated on the rough surfaces and pores of the quartz sand. The element content of the iron oxides, quartz sand and iron oxide coated quartz sand was investigated through scanning electron microscopy/X-ray energy analysis. The results showed that only Fe, Si and O signals can be detected, B element was not detected. EDS quantitative analysis found that the Fe content in oc-B-goethtie coated quartz sand reached 29.51%, which significantly higher than ordinary goethite or ad-B-goethite coated quartz sand.8. Sand culture experiment was conducted to investigate the boron release of the boron from boron-containing oxide and its effect on the boron content of the nutrient solution and rape. It was found that the changes of boron concentration in solution and the changes of water soluble boron content of the oxide is very similar, they all showed a drastic changes at 0-2 days, which was not same is the boron content of the oxides was sharply declined and the boron concentration in the solution was increased. The change of the total boron content of the oxide was relatively eased, it just showed a decline at 6-8 days. The influence of the oxides on the boron content of rape showed a single peak curve pattern. The oxides influenced the nutrient solution pH greatly, the pH of the solution in the two oxides treatment was changed from 5.02 at the initial of the experiment to7.97 and 7.73 at the end of the experiment, respectively.In order to better understand the release of boron from the boron-containing oxides, the curve fitting was conducted and the corresponding parameter was estimated. It was found that the highest correlation between boron release content of the boron-containing oxides and the changes of time is the Elovich equation; the second is parabolic diffusion equation and power function equation. Whereas, the changes of the boron content of the solution was not the same with the boron release content of the boron-containing oxide, which may be due to the absorption of the boron by rape seedling. The influence of the boron-containing oxides on solution pH was similar with the boron release content of the boron-containing oxides. Moreover, the total boron release content and the water soluble release content were all significantly correlated with the increase of the solution pH, which indicated that it must has exist an inherent relationship between the boron release content of the oxides and the changes of the solution pH.
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