常规方法准确测定土壤有效钾素变化可能性的探讨  

A Discussion on the Possibility of Accurate Quantifying the Variation of Available K in the Soils by Common Methods

作　　者：王火焰[1] 朱树国[2] 周健民[1] 吴礼树[2] 杜昌文[1] 陈小琴[1] 

机构地区：[1]中国科学院南京土壤研究所土壤与农业可持续发展国家重点实验室,江苏南京210008 [2]华中农业大学资源与环境学院,湖北武汉430070

出　　处：《土壤通报》2006年第5期954-960,共7页Chinese Journal of Soil Science

基　　金：国家自然科学基金资助(NSFC40201027)

摘　　要：土壤中的有效钾状况通常用1mol L^-1中性醋酸铵提取的速效钾或1mol L^-1硝酸煮沸法提取的缓效钾量来表征。我国农田土壤中近些年来1mol L^-1中性醋酸铵提取的速效钾量呈普遍下降趋势。但土壤中的有效钾素的实际下降值，到目前为止还没有办法通过测土的方法进行准确评估。本文通过室内培养实验，人为改变土壤有效钾量，对常规土壤有效钾测定方法反应土壤有效钾素变化的效果进行了比较和评价。并对硝酸连续提取法准确测定土壤钾素变化的可能性进行了探讨。结果表明，几种提取方式中，以2mol L^-1冷硝酸超声波连续提取10次获得的外源钾变化的回收率最高，达75％～80％。其次是1mol L^-1硝酸100℃水浴法连续提取6次，测钾变化的累计回收率可达75％。如进一步增加提取次数，可能会有限地提高测钾变化的回收率，但随提取次数的增加，提取过程的可操作性和结果的稳定性将显著下降。因而用硝酸作为提取剂，即使是在高温、超声波等方式下，也很难准确测定强固钾能力土壤中有效钾的变化。能够准确测定土壤有效钾素变化的方法必须能将土壤中易发生变化的有效态钾全部提出，并尽量不提取土壤的原生矿物态钾，寻找这一方法将是未来土壤钾素测定工作中值得关注的问题。The availability of K in soil was traditionally measured via extraction with 1 mol L^-1 neutral NH4OAc or 1 mol L^-1 boiling HNO3. The value of NH4OAc - extracted K in most cropland of China had declined during recent decades according to many reports. While the real decrement of K in the soils can not be quantified accurately through the conventional soil testing methods so far. In this paper, the relationship between the amount of K added to soil and the change of tested soil K value was investigated through a laboratory incubation experiment, and the possibility of accurate quantifying of K variation in the soils with HNO3 was disscussed. The results showed that compared with other methods tested, the highest recovery rate of K added to the soil（75% -80% ） was obtained through a sequential extraction with 2 mol L^-1 cold HNO3 for 10 times in ultrasonic wave, and 75% of the recovery rate was obtained through a sequential extraction with 1 mol L^-1 HNO3 for 6 times at 100℃. The recovery rate of added K may increase slowly as the times of sequential extraction increased, but more times of extraction will result in a bad maneuverability of the procedure and great variation of the data. The results indicated that it＇s very difficult to quantify accurately the variation of soil K via HNO3 , extraction with even under condition of 120℃ or with ultrasonic wave. It is suggested that a successful extraction method for accurate quantifying of K variation in soil should be preferential to all the available K rather than the mineral K in soil. To find such a method was still a challenge for the future research.

关 键 词：土壤 钾 测定方法 回收率 

分 类 号：S151.93[农业科学—土壤学]