Six of originally eight long‐term trials in Halle (Saale), Germany, are still continuing. Five are situated at Julius‐Kühn‐Feld, an experimental station launched by Julius Kühn in Halle in 1866. Apart from the Eternal Rye trial established in 1878, those are phosphorus, potassium, lime, and organic fertilization long‐term trials, all being launched by Karl Schmalfuß in 1949. Other long‐term trials have been terminated, but data are available on the effects of nitrogen fertilization and the physiological reaction of fertilizers. Another long‐term trial in Halle (Adam‐Kuckhoff‐Straße 17b) investigates the influence of fertilization on soil formation from loess. Up to now, the major results are as follows: 1. Changes in soil‐ecological properties due to fertilization and rotation were only evident after 30 years, and new steady states sometimes took 70 years to occur. 2. In the long term, the C‐ and N‐contents of the soil largely depend on the amount of hardly decomposable organic matter applied with organic fertilization. High mineral‐N doses, with consequent high crop and root residues, increased the humus content of the soil. 3. Mineral fertilization can replace organic fertilization in terms of sustainable yield capacity provided equal nutrient amounts were applied. 4. The high P‐supply ability of the soil in Halle could not be explained by traditional soil analysis methods of calculating plant‐available P. With some restrictions, the same is valid for K. 5. At the experimental site, soluble salts (nitrate, sulphate) accumulated in the subsoil. 6. A regular lime demand of central German chernozems could be proved, especially in case of low soil organic matter (SOM) and physiologically acid fertilization.

In dem 1878 auf einer Tschernosem‐Braunerde (aus Sandlöß) angelegten Dauerdüngungsversuch Ewiger Roggenbau wurde 1990 die Variante mit ausschließlicher N‐Düngung (N) durch eine solche mit organisch‐mineralischer Volldüngung (Stallmist + NPK) ersetzt. Wegen der in den vorangegangenen 112 Jahren eingetretenen Verarmung des betreffenden Bodens an verfügbarem P und K erfolgte im Herbst 1990 außerdem eine einmalige zusätzliche Gabe von 200 kg P ha−1 und 400 kg K ha−1. Der bis dahin eingetretene Ertragsrückgang von ∼ 30% auf der N‐Variante gegenüber der mineralischen Volldüngung (NPK) oder der alleinigen Stallmistdüngung (St I) wurde bereits im ersten Jahr nach der Umstellung auf St + NPK (Ernte 1991) vollständig überwunden. Mehrerträge bei ST + NPK gegenüber den anderen Varianten (NPK, St I) wurden bisher nur unter besonders günstigen Bedingungen für die Ertragsbildung erzielt, so 1993 und 1995.

Four long‐term mineral fertilization trials (50 years) on a Haplic Phaeozem derived from sandy loess were conducted. Fertilization caused changes to the plough layer (0—25 cm) and to the undisturbed subsoil. Without lime, most remarkable acidification occurred in the plough layer, but only slight effects were evident in the subsoil. Where lime was applied, a considerable amount of Ca‐sulphate was formed. This leached out of the plough layer and accumulated throughout the profile, especially in dry years. Where fertilization was not adequate, there was a substantial contribution of K and P from the subsoil (mainly of its upper parts). Where the supply of these two elements continously exceeded their removal, a distinct increase of available K and P at depths of about 50 cm indicated transfer of both elements to the subsoil. Due to the high fixing capacity of both P and K in layers beneath 50 cm, leaching out of the rooting zone can be ignored. Mg and especially Na, applied with some of the fertilizers, were more mobile than K.

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