Ellmer, Frank

Nielsen, Kerstin

Roß, Christina-Luise

Sensel-Gunke, Karen

Wilken, Verena

English

JKI Open Journal Systems (Julius Kühn-Institut)

11th Young Scientists Meeting 2018, Braunschweig, Germany, November 14-16 Roß et al. Processed biowaste digestates as fertilizer and soil additive in agricultureChristina-Luise Roß1,2, Karen Sensel-Gunke1, Verena Wilken1, Kerstin Nielsen1 and Frank Ellmer21 Berlin Humboldt University, Institute for Agricultural and Urban Ecological Projects (IASP), Berlin 2 Berlin Humboldt University, Department of Agronomy and Crop Science, Berlin E-mail of corresponding author: roschris@agrar.hu-berlin.deIntroduction, Material and Methods Using biowaste in biogas plants is an es-tablished process that will become more important due to the mandatory sepa-rate collection of biowaste in Germany established in 2015. Current policy’s aim is to recycle valuable compounds in di-gestates, which are usually composted and, if necessary, further processed.  To test the effects of such biowaste di-gestates on soil ecology and crop growth a three-year field trial was carried out, which was supplemented by pot experi-ments, experiments with rhizoboxes and phytotoxicological tests. Furthermore, the carbon mineralization rate of the di-gestates was determined using a CarbO2Bot® (prw electronics, Germany), earthworm avoidance tests were per-formed and species and abundance of earthworms were investigated in the field trial. In addition to agglomeration and pellet-ing, various additives (meat-and-bone meal (MBM), Calcium ammonium nitrate (CAN), bentonite, straw) were tested to investigate the possibility of influencing the digestates’ chemical-physical proper-ties. Results • The content of readily available nitro-gen is low. In the pot experiments, theplants withdrew a maximum of only12% of the applied nitrogen.• The digestates contain significantamounts of phosphorus and potas-sium. These are better plant availablethan nitrogen.• After application of the tested prod-ucts, a significant increase in the soil-pH values was detected.• In the soil respiration studies, about20% of the applied carbon was miner-alized in the first 100 days.• The use of composted digestates frombiowaste promotes the activity of mi-croorganisms in the soil.• The investigations in earthwormabundance in the field remained in-conclusive. The avoidance testsshowed no limitation of the habitatfunction within the meaning of the ISOstandard 17512-1 (2008).• A phytotoxicity of the digestates ex-isted only in isolated cases and wasnot dose-dependent, but due to punc-tual contamination.• The addition of nitrogen-containingcompounds such as CAN or MBM sig-nificantly increases the direct fertiliz-ing effect of the products. Dependingon the ammonium content, phyto-toxic effects were observed. These arelarger with the addition of mineral fer-tilizers than with organic N com-pounds. Clay minerals partially re-duced this phytotoxicity.14 Berichte aus dem Julius Kühn-Institut 200

Processed biowaste digestates as fertilizer and soil additive in agriculture

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Processed biowaste digestates as fertilizer and soil additive in agriculture

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