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石灰性土壤的电超滤(EUF)特性主要是浸提时因需控制电流而必须大大降低电压。在一定范围内,降压程度与土壤 CaCO_3%有密切关系。控流限额愈低,电压需成比例地下降,但土壤EUF-值减小不多。电流控制在一定值时,离子的解吸总量亦为定值。控流主要控制了各石灰性土壤解吸/溶解份额特大的 Ca+Mg 量近于定值,对于含量小的其他养分离子则并无多大影响,仍可区辨各土壤间的差别。通过冬小麦盆栽试验和有关化学测试法等方面的相关研究,表明采用国际通用的5g 土样和控电流方法测定 EUF-K 和-P 等有效养分,对于石灰性土壤也是可行的,但其EUF-(Ca+Mg)值则毫无植物营养有效性的意义。土壤 EUF 值只是一种指数,并非真正的解吸离子量。石灰性土壤 EUF-K 值因浸提时降压控流而略低,80℃时5min 内解吸的钾不一定是非交换性钾。由于 Ca-P 和 CaCO_3在高温高电压时浸出较多,故石灰性土壤 EUF-P 和-(Ca+Mg)的80℃值/20℃值之比,与酸性土壤或非石灰性土壤相比要大得多。
Electro-ultrafiltration (EUF) characteristics of calcareous soils are mainly due to the need to greatly reduce the voltage due to the need to control the current during leaching. Within a certain range, the degree of pressure reduction and soil CaCO 3% are closely related. The lower the flow control limit, the voltage should decrease proportionally, but the soil EUF-value decreases little. Current control at a certain value, the total desorption of ions is also a fixed value. Controlled flow mainly controls the amount of Ca + Mg with excessively large amount of desorption / dissolution in calcareous soil near the set value, while it does not have much influence on the other nutrient ions with small content. Differences among the soils can still be distinguished. Through the research of pot experiment in winter wheat and relevant chemical test, it is shown that the effective nutrient such as EUF-K and -P can be measured by the international 5g soil sample and control current method, which is also feasible for calcareous soil. However, EUF- (Ca + Mg) values have no significance of plant nutrient availability. Soil EUF value is only an index, not the actual amount of desorption ions. The EUF-K value of calcareous soils is slightly lower due to the step-down flow control during extraction, and the desorbed potassium in 5 min at 80 ℃ is not necessarily non-exchangeable potassium. Due to the leaching of Ca-P and CaCO_3 at high temperature and high voltage, the ratio of EUF-P and - (Ca + Mg) of calcareous soil at 80 ℃ / 20 ℃ is higher than that of acidic soil or non-calcareous soil To be much larger.