N-Freisetzung von organischen N-Düngern unter überdachten Bracheparzellen

In a two years lasting trial the N-release of organic N-fertilizers should be analysed under covered fallow plots during the vegetation period. The following fertilizers were proved: cattle manure from two locations, “Vinasse” (product resulting from the converting of sugar-beet molasses), “Haarmehlpellets” (pellets of grounded pig bristles), “Rizinusschrot” (grist of the seed of Ricinius communis), “Rapsschrot” (coarse colza meal), “Phytopearls” (residue of maize converting), “Maltaflor” (malt germs and “Vinasse”), “Agrobiosol” (biomass from Penicillium) and “Horndünger” (horn parings in different fractions). In comparison with these organic fertilizers the mineral N-fertilizer calcium-ammonium-nitrate was used. With the exception of the control all variants got an annual N-fertilization of 90?kg?N/ha. The N-mineralisation of the soil caused by the organic substance, which was in the soil before the trial started, amounted to 84?kg?N/ha in the first and to 59?kg?N/ha in the second year of experience. In both years the N-mineralisation was higher in the second half of the vegetation period (July–November) than in the first half (March–July). In the first year the amount of N-release was clearly less than the given quantity of the N-fertilizer with the exception of “Agrobiosol”. Especially the two manure-variants showed N-immobilisation. “Agrobiosol” showed the highest N-release of the tested organic N-fertilizers. In the second year the N-release both of the two manure-variants and of “Rapsschrot”, “Phytoperls”, “Maltaflor”, “Agrobiosol” and “Horndünger” increased clearly. It was between 51 and 101% of the N-quantity given in the second year. N-release was particularly high by “Agrobiosol”, “Horndünger” and “Rapsschrot”. This increase could be traced to the mineralisation of the remained organic substance given in the first year. The variants “Haarmehlpellets” and “Rizinusschrot” had the same N-release as in the first year. The application of “Vinasse” showed a clear decrease. When “Rapsschrot”, “Phytoperls”, “Maltaflor”, “Agrobiosol”, “Horndünger” or manure are given for many years, one can consequently count on an increase of the annual N-mineralisation. Considering the results of both years of the trial the organic fertilizers “Agrobiosol”, “Horndünger” and “Maltaflor” can be classified as quickly effectiveN-fertilizers, “Haarmehlpellets”, “Rizinusschrot” and “Phytopearls” as moderately effective and “Rapsschrot” and “Vinasse” as slowly effective ones.