| Selenium(Se)is an important trace element in the ecological environment,and closely related with public health.Rice(Oryza sativa L.)is the major food staples in the world,and also identified as the most important source of Se intake for human being.In the present study,254 pairs of soil and rice samples were collected from 3 counties of Guangxi province,including Binyang,Shanglin and Nandan,to investigate the soil factors affecting Se accumulation in rice.Moreover,pot experiments were carried out to study the effects of phosphorus(P)and sulfur(S)fertilizations on Se uptake and accumulation in rice.The main results were summarized as follows:1.A statistically significant positive correlation was found between rice grain Se content and soil total Se content,soil water soluble selenite content,soil exchangeable selenite content(p<0.01),and soil available Se content(p<0.05).Thus,contents of soil total Se content,soil available Se,soil water soluble and exchangeable selenite could be used as an index to assess soil Se supply capacity in these investigated areas.2.Soil organic carbon,soil available phosphorus,soil available sulfur and soil available potassium contents had significant negative effects on Se concentration in rice grain.Soil chemiscal factors such as organic carbon content,available P,available S,available K,influence Se uptake in rice plant in these rice producing investigated areas.The inhibitive efficiency on rice absorption of Se in descending order:soil available P>organic carbon>soil available K>soil available S in soil.3.The influence of soil physical and chemical properties on soil Se availability was complex.A significant positive correlation was found between available Se content and Soil pH and organic carbon content.However,soil available sulfur,soil available P,soil available Ca and soil available Mg were the main factors to decrease available Se extracted from soil.4.Single or combined application of P and S fertilizers could significantly reduce Se concentration in rice grain.P and S applications had no significant effects on soil available Se content which indicated that P and S applications could not immobilize of Se in the soil.5.Reasonable application levels of P and S could increase rice grain yield and amount of Se accumulation in rice grain and leaves,and increase the proportion of grain Se in the total accumulation of Se in plant.Under the experimental conditions,104.22 mg/kg soil P2O5,60.795mg/kg soil S(PS4)and 120 mg/kg soil P2O5,70 mg/kg soil S(PS7)two combinations were recommended for Se-enriched production.6,Sulfur fertilization significantly reduced the Se content in rice treated with zero-valent Se.While S fertilization had no significant effect on the Se concentration in rice treated with selenite.Under same S application conditions,there was no significant difference on Se concentration in rice leaves between and zero-valent Se and selenite treatments.However,the Se concentration in rice grain treated by selenite application was significantly higher than that of zero valent selenium treatment.Sulfur application had no effect on Se adsorption in rice leaves treated by zero-valent Se and selenite,but influenced their transport efficiency of Se from leaf to grain.7,The effects of S and different Se fonns applications on rice grain yield depended on soil available S content.When soil effective S content at the low level(<67mg/kg),the grain yield of rice treated with foliar application of zero-valent Se was significantly higher than that of foliar application of selenite;When soil available sulfur content at the medium level(90-100mg/kg),the grain yield of rice treated with foliar selenite was significantly higher than that of spraying zero valent Se;when the soil effective sulfur content at a high level(>100mg/kg),no significant difference in grain yield of rice was found between foliar application of zero valent Se and selenite. |
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