Stickstoffnutzungseffizienz roher und anaerob vergorener Güllen: Eine Studie mit unterschiedlichen 15N Methoden

Summary

In agricultural biogas plants in Switzerland, in general 80 % or more of the digested organic matter is farmyard manure. Organic waste materials are used as cosubstrates. A field experiment with silage maize was conducted to test whether the apparent nitrogen use efficiency (NUE) of anaerobically digested slurries is higher than the one of raw slurries in the year of application. Two different 15N labelling
methods were used. In the 15N direct method, slurry NH4-N was labelled. In the indirect 15N isotope dilution method soil was pre-labelled by incorporating 15N labelled
clover-grass powder; maize received unlabelled slurry. In the 15N direct approach, raw slurries had the lowest apparent NUE of NH4-N, two anaerobically digested (AD)
slurries had an approximately 10 % higher NUE than raw slurries (not all results sign.). The NUE of total N in the non-isotopic difference calculation showed the same
patterns between treatments. In contrast, results gathered with the isotope dilution method showed different patterns. Incorporating clover-grass powder one month before maize sowing seems to be too short to pre-label the soil organic matter homogenously.