[Objective]The extraction efficiency of soluble nitrogen in common moun-tain red soil under different conditions was analyzed to provide experimental refer-ences for the extraction of soil soluble nitrogen.[Method]The fresh soil and air-dried soil,which were the common mountain red soil under evergreen broad-leaved forest vegetation,were used as the experimental materials.The 2 mol/L KCl and 0.5 mol/L K2SO4 were used as the extractants to extract the soil soluble nitrogen with the extractant-to-soil volume ratio at 4:1,6:1 and 10:1,respectively,to examine the extrac-tion efficiency of soluble nitrogen in the experimental soil with different extraction conditions.[Result]Compared with K2SO4,the NH4+-N extracted by KCl was better in quantity and stability;while only at high extractant-to-soil volume ratio could K2SO4 fully extract the soil NH4+-N.The 2 extractants showed small difference in extracting NO3--N,but at low extractant-to-soil volume ratio,the stability of NO3--N extracted by KCl was higher than that extracted by K2SO4.The properties of NO2--N extracted by the 2 extractants were very similar.As for soil SON extraction,there was small dif-ference between the 2 extractants.However,the SON extracted by KCl was fewer in quantity than that by K2SO4,but had higher stability,and the extracted SON amount of the 2 extractants showed significant correlation.The extractant-to-soil ratio had little effect on MBN extraction using K2SO4,but the effect was significant when using KCl to extract MBN.The difference between the extraction efficiency of KCl and K^SO4 in extracting fresh soils was greater than that in extracting air-dried soil;therefore,the extractants should be carefully selected in soluble nitrogen extraction from fresh soil.[Conclusion]The results lay the experimental foundation for improving the extraction efficiency of soil soluble nitrogen and increasing the comparability of measurement results.
Shidong CHENHongliang MARen GAOCongwei YANFangfang LIShuxiang LI
