The Effect Of Boron-Containing Goethite On Nutrient Properties And Acidified Factors Of Red Soil And Its Response In Rape (Brassica Napus L.)

Boron is one of the essential trace elements for plant growth. The interaction between boron and iron oxides in soils will impact on soil micro-environment and plant growth, which also was an important factor affecting soil chemical behavior and plant nutrition of boron. In present study, the reaction of boron and goethite was simulated using gel co-precipitation method. Goethite and two types of boron-containing goethite were synthesized in laboratory:goethite which had boron either adsorbed (ad-B-goethite) or occluded (oc-B-goethite). Original goethite and boron-containing goethite were added to red soil using soil culture method. Through setting the different treatment, we observed the effect of boron-containing goethite on the growth of seedling and harvest time of rape and apparent biomass; studied the effect of boron-containing goethite on acidified ion of soil and other soil properties; studied the release characteristics and bioavailability of boron of boron-containing goethite in soil using the test of isotope. The main findings were as follows:1. The content of HWSB and total boron of oc-B-goethite were higher than that of ad-B-goethite. The proportion of available boron and total boron of that was lower than ad-B-goethite. The release and uptake for plant of boron in ad-B-goethite was easier than that in oc-B-goethite. The increase of BET of different types of oxides was in order of: oc-B-goethite>goethite>ad-B-goethite. The bands of Fe-OH-Fe in-plane bending and parts of the adsorption peak were weak compared with the original goethite. Ad-B-goethite maintained the structure of goethite, and the structure of oc-B-goethite was changed.2. Boron-containing goethite increased the dry accumulation of shoot and root of rape at different growth stages. The growth situation of rape of boron-containing goethite was better than that of boron treatment and goethite treatment. Boron-containing goethite increased the first effective number of branch and the harvesting coefficient of rape. Plant height and the first effective branch height decreased in boron-containing goethite treatment compared with other treatments. Different types of oxides at different growth stages of rape had different effect on the rape growth.3. Boron-containing goethite increased the content of HWSB and boron supply capacity of soil, which could continue to meet the needs of rape for boron at the whole growth period. The increase of HWSB content promoted the uptake of boron for rape. The content of HWSB of soil and boron content of rape are closely related with dry matter accumulation, which indicated that it was an important reason for the increase of boron uptake and rape biomass to increase the HWSB content. 4. Boron-containing goethite increased soil pH and decreased soil exchangeable acid content. Soil pH in harvest time was higher than that in rape seedling. Different types of oxides were in order of:oc-B-goethite>ad-B-goethite>goethite. Boron-containing goethite impact the exchangeable H+ more obvious than the exchangeable Al3+. The increase of soil pH and the decrease of exchangeable acid were closely related to rape biomass, indicating that the increase of soil pH and the decrease of soil exchangeable acid was another important reason for the better growth of rape.5. Boron-containing goethite decreased the content of soil active Al and Mn, and the result in rape seedling was more significant than that in harvest time. The decrease of soil active Al content in rape seedling and active Mn content in harvest time reduced the uptake of Al and Mn for rape. Soil active Al content in rape seedling was significantly positive correlated with Al content of rape and active Mn content in harvest time was significantly positive correlated with Mn content of rape. Boron-containing goethite changed the status of different forms of manganese in the soil and the content of non-active manganese for plants increased, which reduced the uptake of manganese for plant and improved the growth of plant.6. Although the increase of HWSB could not reduce the content of soil active Al and Mn, the uptake of boron for plant was favorable to inhibiting the effect of Al and Mn toxicity on rape growth. There was no correlation between the content of soil Al or Mn and HWSB content, but Al and Mn content in rape was significantly negative correlated with boron content in rape. Boron-containing goethite could decrease the content of active Al and Mn in soils, reduce the supply capacity of soil Al and Mn, especially could improve the availability of soil boron through the increase of provision of boron nutrition to inhibit the toxicity of Al and Mn, which promoted plant growth. The stepwise regression analyses indicated that the increase of soil pH and the decrease of soil exchangeable H+ and active Mn content provided a better soil micro-environment for rape seedling growth; soil pH and active Al in harvest time of rape had a more important effect on the soil acid environment.7. Boron-containing goethite impacted different forms of phosphorus content, especially for Org-P. The content of soil Al-P,Fe-P,Org-P was highly related to phosphorus uptake and dry matter accumulation of rape. The effect of different forms of phosphorus on phosphorus uptake of different parts of rape and dry matter accumulation were different. The decrease of phosphorus content of stem and the increase of soil Org-P were the important reason of height of rape decreased in boron-containing goethite treatment.8. Boron-containing goethite mainly existed in crystalline state in soils. Ad-B-goethite was favorable to active in rape seedling and oc-B-goethite was favorable to active in harvest time. The increase of Feo and Fed content of soil in rape seedling impacted Al-P and EXC-Mn content of soil. The increase of Fed content in harvest time impacted Al-P and Org-P content. The increase of Feo content benefited O-Fe-P release increasing the available of occluded phosphorus, while impacted the content of OM-Mn and RO-Mn. The activation of boron-containing goethite impacted the phosphorus and manganese forms, which would not impact the boron desorption. Uptake and utilization of Fe for rape also did not appear adversely affected.9. Boron-containing goethite could increase the content of different forms organic matter; high labile organic matter was significantly correlation with HWSB, and affected the uptake of boron for rape. The effect of soil different forms organic matter on different forms phosphorus mainly was the effect of high and low labile organic matter on Al-P and Org-P. Low and middle labile organic matter was main component for the effect of soil different forms Mn.10. Boron-containing goethite improved the available Ca and Mg content; the uptake of Cu and Zn of rape root increased and the uptake of Cu and Zn of rape shoot decreased. Stepwise regression analysis showed better soil environment for boron supply and lower active Al and Mn content was favorable to rape root growth, while decrease of Ca and Al content and increase of Mg uptake was favorable to rape shoot growth.11. Condition with plants or no plants, the amount of 10B release in boron-containing goethite treatment continued to increase; oc-B-goethite had a higher 10B release amount than ad-B-goethite. The treatments for plants was favorite to increasing the release of 10B of boron-containing goethite. Rape shoot and root biomass continued to increase, while the accumulation of 10B uptake for rape was in keep with the release of 10B of boron-containing goethite. Therefor, the release of 10B was favorable to uptake of 10B for rape. Fitting result of kinetic equations showed that in condition with no plants zero-rate equation and parabolic diffusion equation fitted the rules of 10B release in ad-B-goethite treatment better than other equations, while first order rate equation fitted the rules of 10B release in oc-B-goethite treatment better than other equations. in condition with plants, zero-order, first-order and parabolic diffusion equation fitted to describe the rules of 10B release of ad-B-goethite and oc-B-goethite in the soil. Among them, first-order equation fitting 10B release rules of oc-B-goethite was highest of all. The release rate of 10B in ad-B-goethite is faster in short term, while The release rate of 10B in oc-B-goethite is consistently higher in long term, which was correspond to the activation characteristics of boron of boron-containing goethite in soil.