Effect of liming central European loess soils on soil extractable phosphorus and potassium as determined by electro-ultrafiltration

The benefits of liming acidic or calcium (Ca)-deficient soils for soil structure and fertility are well documented. However, little is known about the effect of liming nearly neutral loess soils – lacking Ca – on interactions between soil nutrients. Over a 2-year period, 62 field trials were conducted in Germany and Austria with three treatments (0, 3 and 12 t CaO ha^?1) on slightly acidic loess soils. Soil samples from the top soil layer were taken 4, 8, 16 and 24 weeks after liming. In addition to the pH_CaCl2, the phosphorus (P), potassium (K) and Ca contents were analysed using electro-ultrafiltration (EUF). The application of lime increased the pH in average from 6.6 up to 7.0 and 7.2, but did not decrease EUF extractable P and K below the level of untreated control. Contrary to our expectations, EUF extractable P increased 4 weeks after liming in the treatment with 3 t CaO ha^?1. At the end of incubation period, 24 weeks after liming, the EUF extractable K in treatment 12 t CaO ha^?1 remained still 1.3 mg K 100 g^?1 soil above the untreated control.