贮存温度和时间对风干土壤钾素测定值的影响

为正确评估土壤钾素测定值的时效性,采用培养试验研究了4种贮存温度条件(室温、4℃低温、25℃恒温、60℃干燥)下,3种不同类型风干土壤样品钾素测定值随贮存时间的动态变化。结果表明:不同形态钾素测定值受贮存温度和时间的影响显著。不同贮存温度条件下,随贮存时间延长水溶性钾的测定值相对培养前的测定值(初始值)变幅不一致,在室温培养条件下变幅较小,4℃低温培养和60℃干燥培养条件下变幅较大;交换性钾测定值在60℃干燥培养条件下相对初始值的变幅较大,在室温和25℃恒温培养条件下变幅较小;非交换性钾的测定值在4℃低温培养条件下变幅较小,在室温、25℃恒温和60℃干燥培养条件下相对初始值的变化均较大。不同形态钾素间的转化受贮存温度和时间的影响显著,4℃低温条件下长期贮存的土壤样品中水溶性钾、交换性钾的测定值均增加;室温和25℃恒温条件下长期贮存的土壤样品中水溶性钾与交换性钾之间存在动态平衡;长期贮存在60℃干燥培养下的土壤样品,随贮存时间的延长有少量非交换性钾转化为交换性钾。可见,贮存温度和时间对风干土壤钾素测定值影响较大,其测定值具有时效性。

Effects of Storage Temperature and Time on Test Values of Potassium in Air-dried Soil

In order to correctly evaluate the timeliness of soil potassium (K) test value, this paper studied the dynamic changes of potassium test value in soil samples dried by different forms through culture experiment under 4 types of storage temperature (room temperature, 4℃ low temperature, 25℃ constant temperature, 60℃ dry incubator). The results showed that: Storage temperature and time could significantly affect the test values of different K forms. Under different storage temperature, along with the extension of storage time, the test value of water soluble K was different from that of before culture (the initial value). Under room temperature, the variation relatively to the initial value was smaller, and it was greater under 4℃ low temperature and 60℃ dry incubator. The test value of exchangeable potassium under 60℃ dry incubator had larger variation relatively to the initial value; while the variation under room temperature and 25℃ constant temperature were smaller. The test value of nonexchangeable K had smaller variation under 4℃ low temperature, and it had a larger variation than the initial value under room temperature, 25℃ constant temperature and 60℃ dry incubator. The transformation of different K forms was significantly affected by storage temperature and time. The water soluble K, exchangeable K values were increased under 4℃ low temperature; and there was a dynamic balance between water soluble K and exchangeable K when the soil samples stored at room temperature and 25℃ constant temperature conditions; with the extension of storage time, the nonexchangeable K was converted into exchangeable potassium under 60℃ dry incubator for long period of time. In conclusion, storage temperature and time significantly affected air-dried soil K test value, and K test value had timeliness.