| Selenium(Se)is one of the 14 essential trace elements in human body.The decline in human function and negative effect on human health will be triggered because of Se lack.Se deficiency was found in many countries around the world,such as China.Fortunately,There were several Se-rich areas(Se content ?0.400 mg·kg-1)investigated in southern China,as Enshi in Hubei province,Fengcheng in Jiangxi province,Zhaoan and Datian in Fujian province.The Fujian Se-rich soil area is about 32,600 square kilometers.Some studies have shown that Se-rich soil does not necessarily produce Se-enriched crops.Only the available Se in soil could be absorbed by crops.Therefore,in order to produce the Se-enriched crops,it is very important to improve the effectiveness of soil Se.In this thesis,the Se-rich soils were collected for soil culture and pot experiment,to study the effects of pH change,humic acid,dry-wet alternation and exogenous Se on the availability of soil Se,the distribution of soil Se forms,and its absorption characteristics in crops,to provide a theoretical basis for the production of Se-enriched crops in Se-rich soil.The main results were as follows:(1)In different soil pH treatments,the contents of soil available Se were followed by pH9.0(81.8-87.0 ?g·kg-1),pH7.5(53.3?62.5 ?g·kg-1),pH6.0(43.5?5.1 ?g·kg-1)and pH4.5(36.5?46.2 ?g·kg-1)from high to low in the order.And the pH value showed a very significant positive correlation with soil available Se content in each sample time.The proportion of the bound to organic matter and sulfide Se was the highest,and followed by the bound to Fe-Mn oxides and the residual Se,the exchangeable and bound to carbonates Se,the water-soluble Se in all treatments.The soil pH value had significant positive correlations with the exchangeable and bound to carbonates Se,the water-soluble Se,and significant negative correlation with the bound to organic matter and sulfide Se,and no relationship was found with the bound to Fe-Mn oxides and residual Se.In the treats of pH 6.0 and 7.5,the biomass,root length and leaf area of Chinese cabbage were the highest,followed by the pH 9.0 and pH 4.5 in the order.The leaf Fv/Fm values reached a peak at pH 6.0 and 7.5,followed by pH9.0 and 4.5.At the same time,the Fv/Fm values of the new leaves were higher than those of the old leaves.The Se contents in plant roots were higher than those in the above-ground.The Se contents in all parts were increased with the increase of soil pH value.The Se contents in the fresh weight of edible part were ranged from 0.002 mg kg-1 to 0.013 mg kg-1.(2)In differentr dry-wet alternation pot treatments,the contents of soil available Se were followed by CK(keep soil moisture at 20%)(37.5?37.6?g kg-1),T3(heavy dry and wet alternately)(29.0?33.1?g·kg-1),T2(light dry and wet alternately)(24.9?26.8 ?g·kg-1),T1(keep the soil water layer 1-2 cm)(15.8?16.0 ?g·kg-1).The height,tiller and effective panicle numbers of rice plant were all followed by ck(flooding before the grouting period,light dry and wet alternately after the grouting period),t2(light dry and wet alternately),t3(heavy dry and wet alternately),ti(keep the soil water layer 1-2 cm),while the yield was showed by t2,ck,t3,ti in the order.The Se contents in different parts of rice were followed by root,stem,leaf,husk,rice.In the treatments,they were followed by t3(0.185?0.695 mg·kg-1),t2(0.181?0.573 mg·kg-1),ck(0.158?0.491 mg·kg-1),ti(0.132?0.411 mg·kg-1).There were significant positive correlations between soil available Se contents and Se contents in various parts of rice.(3)With the increases of the amounts of humic acid,the soil available Se contents were also increased.In the process of soil culture,the Se contents were followed by 20%OM(43.3-50.6 ?g·kg-1),10%OM(37.6?48.8 ?g· kg-1),5%OM(36.0?44.1 ?g·kg-1),CK(33.0?41.5 ?g·kg-1).The Se forms in all treats soils were showed that,the proportion of the bound to organic matter and sulfide Se and residual Se were the highest,followed by the bound to Fe-Mn oxides Se and the exchangeble and bound to carbonates Se,the lowest was the water-soluble Se.There were significant positive correlations between soil organic matter content and water-soluble Se,exchangeable and bound to carbonates Se,the bound to organic matter and sulfide Se,and negatively correlated with the bound to Fe-Mn oxides Se and residual Se.The gray correlation analysis of soil organic matter content as the parent sequence also showed that the correlation between water-soluble Se and organic matter was the highest,followed by the bound to organic matter and sulfide Se,again exchangeble and bound to carbonates Se,residual Se and the bound to Fe-Mn oxides Se.The Se contents of different parts of garlic were followed by root,stem and leaf.With the amounts of humic acid increased,the contents of Se in roots,stems and leaves of garlic were also increased.(4)While added Se in the soil,the contents of soil available Se also increased with the increase of soil pH value.The soil available Se contents in the whole cultures were in the order of SepH9.0,SepH7.5,SepH6.0 and SepH4.5.The Se contents in the same parts of Chinese cabbage were followed by SepH9.0,SepH7.5,SepH6.0 and SepH4.5.The contents of soil available Se were showed by SeCK(keep soil moisture at 20%),SeT3(heavy dry and wet alternately),SeT2(light dry and wet alternately),SeT1(keep the soil water layer at 1-2 cm)in the order.The contents of Se in different parts of rice were followed by root,stem,leaf,husk and unhusked rice.At the same time,the contents of Se in the same parts of rice were followed by Set3(heavy dry and wet alternately),Set2(light dry and wet alternately),Seck(flooding before the grouting period,light dry and wet alternately after the grouting period),Set1(keep the soil water layer at 1-2 cm).Throughout the whole culture process,the contents of soil available Se were followed by Se20%OM,SelO%OM,Se5%OM,SeCK.The contents of Se in different parts of garlic were followed by roots,stems,leaves.And the contents of Se in different parts of garlic were all followed by Se20%OM,Se10%OM,Se5%OM,SeCK.In addition,the contents of soil available Se that with exogenous Se were higher than that without adding exogenous Se,so as those in the absorption of crops. |
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