普通山地红壤可溶性氮不同条件下的提取效率比较

目的]针对目前土壤可溶性氮的提取方法在提取剂种类、水土比及土样保存状态(新鲜和风干)等方面的不同,分析普通山地红壤可溶性氮不同条件下的提取效率,以期为土壤可溶性氮提取提供试验依据。方法]利用常绿阔叶林植被下普通山地红壤,分别以其新鲜土和风干土为试验材料,探讨2 mol/L KCl和0.5 mol/L K2SO42种提取剂在水土比4∶1、6∶1和10∶1下提取土壤可溶性氮的差异,研究该类型土壤可溶性氮不同提取条件下的提取效率。结果]KCl比K2SO4更适合用于提取土壤NH4+-N,KCl提取的NH4+-N不仅量大且稳定性好,K2SO4则需在较大水土比下才能充分提取土壤NH4+-N;2种提取剂在NO3--N提取上的差异性很小,但低水土比下KCl提取NO3--N的稳定性高于K2SO4;两者提取的NO2--N性能非常接近;在土壤SON的提取中,2种提取剂的差异较小,KCl提取的SON量少于K2SO4,但稳定性高于K2SO4,二者的SON提取量具有极显著相关性;用K2SO4提取MBN时可以不考虑水土比的影响,但使用KCl则必须慎重选择水土比。提取新鲜样时KCl和K2SO4之间的差异大于提取风干样时的差异,所以在对新鲜样中可溶性氮提取时应更注重提取剂的选择。结论]该试验结果为提高土壤可溶性氮的提取效率,增加测定结果的可比性奠定了试验基础。

Extraction Efficiency of Soil Soluble Nitrogen under Different Conditions

Objective] The extraction efficiency of soluble nitrogen in common mountain red soil under different conditions was analyzed to provide experimental references 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 tow 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 extraction 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 two 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 two extractants were very similar.As for soil SON extraction,there was small difference between the two 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 two 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 K2SO4 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.