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Tropentag, October 5 - 7, 2011 in Bonn

"Development on the margin"


Influence of Biochar and Tannin Amendments to Goat Manure on Gaseous C and N Emissions

Mariko Ingold1, Anne Schiborra2, Eva Schlecht2, Andreas Buerkert1

1University of Kassel, Organic Plant Production and Agroecosystems Research in the Tropics and Subtropics, Germany
2University of Kassel / Georg-August-Universität Göttingen, Animal Husbandry in the Tropics and Subtropics, Germany


Abstract


In subtropical irrigation agriculture year-round high temperature and soil moisture lead to high microbial turnover of organic matter and thus potentially high losses of nitrogen (N) and carbon (C) by gaseous emissions. To investigate the effect of biochar and tannin amendments to manure on gaseous losses of N and C, an incubation experiment was conducted in a climate chamber over 10 days during which air temperature and humidity were kept at 30°C and 50%, respectively. Soil moisture was adjusted every 24h to 60% field capacity. Goat manure was amended with biochar and tannins at two different concentrations through addition (i) to the goat feed and (ii) directly to dried goat manure, before its application to the soil at a rate equivalent to 0.25 and 0.8 t biochar ha-1, and 0.4 and 1.0 t tannins ha-1. Soil emissions of NH3, N2O, CO2 were measured for the amended and unamended manure treatments and for pure soil using a closed chamber system connected to a photo-acoustic infrared multi-gas monitor.Maximum N2O flux rates varied from 0.62-1.06 mg h-1 m-2 and were only decreased for tannins fed to goats by 42% compared to unamended manure (control). Despite this, flux rate peaked 48hrs later for tannins mixed to manure compared to the control treatment and, in contrast, 72hrs earlier for biochar fed to goats. Total N emissions, (60% as N2O-N and 40% as NH3,-N) ranged from 42-78 g m-2 10d-1. Emission peaks of CO2 were not temporally shifted, but distinctly lowered by biochar (42%) and tannins (20%) fed to goats compared to the control treatment. In contrast, direct addition of biochar and tannins to manure enhanced CO2-C by 14 and 24%, respectively. Total C emissions ranged from 40-75 g m-2 10d-1 (97% as CO2-C). CH4 and NH3 emission rates and cumulative emissions of all manure treatments did not differ from emissions of the pure soil. The causes of the contrasting effects of the two application modes of biochar and tannins on CO2 and N2O emissions merit further research.


Keywords: Biochar, carbon, gas emissions, nitrogen, tannin


Contact Address: Mariko Ingold, University of Kassel, Organic Plant Production and Agroecosystems Research in the Tropics and Subtropics, Steinstrasse 19, 37213 Witzenhausen, Germany, e-mail: ingold@uni-kassel.de


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