Über den Einfluß einer gesteigerten Gülledüngung auf Gehalt und Qualität der organischen Bodensubstanz sowie auf den Ertrag

Abstract

Summary On the basis of three two-factorial field trials (1966–1979) on gleyic luvisol the influence of increased slurry application on yields and on the content and quality of organic matter in the soil was investigated. Changes in humus content take place depending on the quantity of slurry organic dry matter applied, the various crop rotations used and the initial organic-matter content of the soil. Thus, in a rotation with 33 % grass, for example, a complete substitution of mineralization can be achieved even with relatively low applications of slurry organic dry matter whereas in the case of alternating root crop and cereal cultivation this could only be achieved by applying extremely large amounts of slurry, which are in actual fact impracticable. Within the practicable range of fertilizer use the combined application of slurry and mineral fertilizer as opposed to the exclusive application of slurry has the advantage that higher yields can be obtained at a similar level of humus reproduction. The qualitative characteristics of soil organic matter investigated in the selected variants over a twelve-year trial period in each case indicate that increasing slurry application has on the whole a positive effect. This is reflected in a higher degree of humification with increasing or at least constant proportions of total humic acid. With the aim of achieving high crop yields parameters for the combination of slurry and mineral fertilizer nitrogen and the substitution of these nitrogen sources in long-term application can be derived from two trials involving pig slurry. In rotations with alternating root crop and cereal cultivation the application of pig and cattle slurry leads to high yields at a similar level so that the origin of the slurry does not appear to have any significant effect on long-term yields.