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Tropentag, September 20 - 22, 2017 in Bonn

"Future Agriculture: Social-ecological transitions and bio-cultural shifts"

Effects of Biochar on Gaseous Carbon and Nitrogen Losses During Composting of Farm Residues in Northern Ghana

Delphine Manka'abusi1, Volker Häring2, Christoph Steiner1, Bernd Marschner2, Andreas Buerkert1

1University of Kassel, Plant Production and Agroecosystems Research in the Tropics and Subtropics, Germany
2Ruhr-Universität Bochum, Inst. of Geography, Soil Science and Soil Ecology, Germany


Adding biochar to nutrient rich organic matter during composting reportedly reduces nitrogen (N) volatilisation and carbonisation of feedstock stabilises organic carbon (C). A biochar-compost may thus foster lasting soil organic matter build-up while providing nutrients to crops. We studied the effects of biochar, produced from on-farm waste materials as compost additives on gaseous C and N fluxes under the Sudanian conditions of northern Ghana. Three biochar types (corn cobs, cCC; rice husks, cRH; and wood, cWO) and their uncharred feedstocks (CC, RH and WO), were co-composted with poultry manure (15 vol-%) and rice husk straw (60 vol-%) in randomly allocated 1 m3 compost bins. During 34 days of composting, emissions of C (CO2-C) and N (N2O-N and NH3-N) were measured using a closed chamber system composed of a photo-acoustic infrared gas analyser (INNOVA 1312-5). Biochar amended composts showed higher CO2-C emission rates during the initial composting phase. Emissions ranged from 8 to 17 g C m-2 h-1 in cRH, and 8 to 12 g C m-2 h-1 for RH. This indicated higher microbial activity in biochar treatments. Respiration significantly dropped during the later days of composting with lower emission rates in cRH (5 g C m-2 h-1) and cCC (3 g C m-2 h-1) compared to their un-carbonized feedstocks with 9 and 11 g C m–2 h–1, respectively. Total CO2-C losses were 14 kg C m-2 34 d-1 for RH and 9 kg C m-2 34 d-1 for cRH resulting in a 33% reduction (p<0.05). Emissions were 9 and 10 kg C m-2 34 d-1 for cCC and CC while cWO and WO emitted 8 and 9 kg C m-2 34 d-1, respectively. This reduced turnover is likely a consequence of the high biochemical stability of biochar-C. Volatilisation of NH3-N was significantly lower in compost containing cWO (93 g N m-2 34 d-1) compared to WO (174 g N m-2 34 d-1), while N2O-N emissions were lower in compost mixtures containing cRH (35%), cCC (9%), and cWO (16%) compared with their uncharred feedstock.

Keywords: Biochar-compost, carbon losses, nitrogen losses, northern Ghana

Contact Address: Delphine Manka'abusi, University of Kassel, Plant Production and Agroecosystems Research in the Tropics and Subtropics, Steinstrass 19, 37213 Witzenhausen, Germany, e-mail: del_fusi@yahoo.com

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