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Tropentag, September 14 - 16, 2022, Prague

"Can agroecological farming feed the world? Farmers' and academia's views."


Increased fulvic acid concentration explains aggregate-associated carbon and nitrogen accumulation in a biochar-amended tropical soil

Emmanuel Amoakwah1, Emmanuel Arthur2, Kwame Agyei Frimpong3

1CSIR - Soil Research Institute, Land Evaluation, Ghana
2Aarhus University, Agroecology, Denmark
3University of Cape Coast, College of Agriculture and Natural Sciences, Dept. of Soil Science, Ghana


Abstract


Humic substances contribute largely to C and N sequestration by enhancing the accumulation of aggregate-associated C and N. However, the response of humic substances and aggregate-associated C and N to biochar application is less studied in the tropical ecosystem. A field experiment was conducted to investigate the effects of corn cob biochar on aggregate stability and humic substances, and how these humic substances impact on aggregate-associated C and N in a tropical ecosystem. The treatments included control/no biochar (CT), 15-ton biochar ha−1 (BC-15), 30-ton biochar ha−1 (BC-30), and 30-ton corn cob biochar ha−1 + phosphate fertiliser (BC-30 + P). The BC-30 and BC-30+P plots significantly increased the concentrations of the humic substances (humic and fulvic acids) compared to the CT. There was a significant increase in the mean weight diameter by 153 and 288% in the BC-30 and BC-30+P treated soils was recorded. The BC-30 treatment resulted in a significant increase in the structural coefficient by 215 and 274%, respectively, in the BC-30 and BC-30+P treatments relative to the CT. Significant increases in the aggregate-associated C and N accumulation were observed in the macro aggregates of the biochar-treated soils. The most important soil property that greatly contributed to the accumulation of aggregate-associated C and N was the fulvic acid – C, and, therefore, it could be used as an indicator to detect early accumulation of C and N in larger aggregates of soils of the humid tropics. Though the applied biochar increased the aliphatic and aromatic C compounds, it is the aliphatic C compound (fulvic acid) that largely and most significantly influenced early C and N accumulation within the macro aggregates in the shortest time.


Keywords: C and N stoichiometry, degree of polymerisation, geometric mean weight diameter, humic acid, humic substances, structural coefficient


Contact Address: Emmanuel Amoakwah, CSIR - Soil Research Institute, Land Evaluation, Academy post office pmb, 00233 Kumasi, Ghana, e-mail: emmaamoakwah@yahoo.co.uk


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