Analyse der K-Düngewirkung an einem Humuspelosol-Standort

Analysis of the K-fertilizing effect on a Humuspelosol site The result of a K-fertilizing experiment with a nearly pure cereal rotation on a Humuspelosol (eutric Cambisol) 1973 poor in ?available”? K and strongly K fixing (see Fig. 1) was analysed by investigating plant and soil samples taken 1981 and 1982. About 1200 kg K₂₀/ha were fixed, thus did not change the ?available”? K, but restored the reserves to such an extent that the plants were supplied sufficiently from it. Amounts exceeding 2400 kg K₂O/ha could not be held in the main rooting space (0–40 cm). Even 180 kg K₂O/ha/a in the course of the experiment restored the reserves sufficiently, leading to an (at best) normal fertilizer requirement at this site (with low Mg supply possibly limiting the yields), despite its still low content of ?available”? K. Apparently, here the LUFA threshold values are too high and/or the lactate method is not a suitable basis for statements about the fertilizer requirement.