Nitrogen availability of various biogas residues applied to ryegrass

• Published in: Journal of plant nutrition and soil science 2013-08, Vol.176 (4), p.572-584
• Main Authors: Fouda, Sara, von Tucher, Sabine, Lichti, Fabian, Schmidhalter, Urs
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; biogas digestates; biogas effluents; Biological and medical sciences; C : N ratio; Chemical, physicochemical, biochemical and biological properties; Fertilizers; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; N uptake; Nitrogen; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments
• ISSN: 1436-8730; 1522-2624
• DOI: 10.1002/jpln.201100233

Biogas plants in Germany are producing an increasing amount of biogas residues to be recycled via agricultural crop production. To test whether the wide range of various substrates used in the anaerobic digestion can affect the chemical composition and nutrient availability, seven biogas residues derived from different substrates were investigated with respect to their N supply to ryegrass. Both the short‐term and the long‐term N availability were studied in a 309‐d pot experiment lasting for five successive growth cycles each starting with a fertilizer application. The organic fertilizers were applied based on an equal amount of ammonium‐N (300 mg N per pot) and compared to mineral N from ammonium nitrate of equal dosage. Biogas residues varied greatly in their chemical composition (ammonium‐N 0.20% to 0.51%, Ntotal 0.36% to 0.75%, and Corg 1.85% to 4.75% in fresh matter). After the first growth cycle, the N availability of the biogas residues applied based on ammonium‐N was at least equal to that from ammonium nitrate. Differences in N offtake after one fertilizer application were negatively correlated to the Corg : Norg ratio of the organic fertilizers. After five successive fertilizer applications, the N utilization of most of the organic fertilizers was increased compared to that of the mineral fertilizer. It is concluded that biogas residues provide plant‐available N at least corresponding to their ammonium content and that the accumulation of organic N in soil through repeated application of biogas residues contributes to N release.