Effect Of Phosphate Application On Soil Selenium Fractions And Selenium Uptake,translocation In Wheat

[Object] Selenium is an important trace element for humans and animals.It is an effective method to increase the crops Se content by improving the soil available Se content.This study include the collect experiment and pot experiment.Analysis of the factors affecting the availability of selenium in soil,study the effect of coapplication of either selenite or selenate with phosphorus and application different of phosphorus types on Se bioavailability of soil.The objective is to explore the effect of phosphate application on soil Selenium fractions and Selenium uptake,translocation in wheat to provide a basis for improve the selenium utilization in the soil.[Method] Pot experiment:(1)Coapplication of either selenite or selenate with phosphorus: The experiment consisted of a 3×2×3 factorial design with three P application amounts(0,1,and 2 g/kg as NH4H2PO4),two types of Se fertilizer(sodium selenite and sodium selenate),and three Se application amounts(0,1,and 2 mg/kg).There were eighteen treatments in total.Each treatment was replicated five times.(2)Different of phosphorus types: Four types of phosphorus fertilizer(Ammonium dihydrogen phosphate,Diammonium hydrogen phosphate,urea phosphate,ammonium polyphosphate),two P application rate(0 and 1 g/kg).[Result](1)The results showed that the total selenium content ranged from 0.142 mg/kg to 1.153 mg/kg-1.The available selenium content of soil ranged from 17.47 ug/kg to 84.09 ug/kg.The wheat grain selenium content ranged from 0.004 mg/kg to 0.055 mg/kg.there was no correlation between total selenium content in soil and wheat grain selenium content,But soil availability selenium and wheat grain Selenium content have significant correlation.Soil availability selenium and soil pH and soil available phosphorus have significant correlation.(2)In the selenite treatment,Soluble Se and exchangeable Se decreased significantly as P application increased within the same selenite treatment.The Fe oxide-bound Se and organic matter-bound Se decreased as P application increased in the 0 mg/kg selenite treatment.In contrast,Fe oxide-bound Se and organic matter-bound Se increased as P application increased in the 1 and 2 mg/kg selenite treatments,1 g/kg P had no significant effect on Se utilization.However,2 g/kg P significantly reduced Se utilization by 50.7% in the 1.0 mg/kg selenite treatment and by 55.6% in the 2.0 mg/kg selenite treatment.P fertilizer reduced Se concentrations in each wheat organ.The largest decreases were in the high selenite treatment,where low P(1 g/kg)and high P(2 g/kg)reduced Se concentrations in roots,stems,leaves,and spikes by33.3%,34.5%,51.6%,34.3% and 71.3%,72.1%,80.6%,73.8%,respectively,compared with 0 g/kg P.(3)In the selenite treatment,the soluble Se,exchangeable Se,Fe oxide-bound Se and organic matter-bound Se fractions decreased as P application increased within the same Se treatment.In the 1.0 mg/kg selenate treatments,P application increased Se utilization by 96-128% compared with the no P treatment.In the 2.0 mg/kg selenate treatments,P application increased Se utilization by 78-123% Selenium concentrations in each wheat organ increased as P application rates increased.The largest increases were in the low selenate treatment,where high P increased Se concentrations in roots,stems,leaves,and spikes by 23.0%,17.0%,64.6% and 62.1%,respectively,compared with 0 g/kg P.(4)In the two kinds of soil that selenium content is 0.308 mg/kg and 1.153 mg/kg condition,Application NH4H2PO4(Ammonium dihydrogen phosphate)treatment decreased exchangeable Se concentrations 8.7%,18.1% respectively,Fe oxide-bound Se concentrations 12.3%,20.7%,respectively,Organic matter-bound Se concentrations 23.4%,22.0%,respectively compared with 0 g/kg P.Application(NH4)2HPO4(Diammonium hydrogen phosphate)treatment decreased exchangeable Se concentrations 17.3%,22.8% respectively,Fe oxide-bound Se concentrations 11.1%,18.5%,respectively,Organic matter-bound Se concentrations 18.5%,21.8%,respectively compared with 0 g/kg P.Application CO(NH2)2·H3PO4(urea phosphate)and(NH4PO3)n(ammonium polyphosphate)treatment have no significant impact on soil Se fractions.(5)When soil selenium content is 1.153 mg/kg,Application NH4H2PO4(Ammonium dihydrogen phosphate)and(NH4)2HPO4(Diammonium hydrogen phosphate)treatments increase the wheat of root Se content79%,81% respectively,stem Se content86.6%,81% respectively,leaf Se content 68.6%,81.8% respectively,spike Se content123.5%,176.5% respectively compared with 0 g/kg P.When soil selenium content is 0.308 mg/kg,Application NH4H2PO4(Ammonium dihydrogen phosphate)and(NH4)2HPO4(Diammonium hydrogen phosphate)treatments increase the wheat of root Se content 53.3%,66.7% respectively,stem Se content 85.7%,157.1% respectively,leaf Se content 30.4%,53.6% respectively,spike Se content138.9%,222.2% respectively compared with 0 g/kg P.Application CO(NH2)2·H3PO4(urea phosphate)and(NH4PO3)n(ammonium polyphosphate)treatment have no significant impact on Se content of wheat.organ.` [Conclusion] In the selenite treatments,P fertilizer significantly reduced Fe oxide-bound Se concentrations and Organic matter-bound Se concentrations causing declines in selenite bioavailability.In the selenite treatment,P activation of Fe oxide-bound Se and organic matter-bound Se causing increase in selenate bioavailability in P-fertilized.Application NH4H2PO4(Ammonium dihydrogen phosphate)and(NH4)2HPO4(Diammonium hydrogen phosphate)can reduce Se adsorption on the soil surface and increase Se bioavailability.