Short-term dynamics of carbon and nitrogen using compost, compost-biochar mixture and organo-mineral biochar

This study aims to examine the effects of different organic treatments including compost (generated from cattle hide waste and plant material), compost mixed with biochar (compost + biochar) and a new formulation of organo-mineral biochar (produced by mixing biochar with clay, minerals and chicken manure) on carbon (C) nitrogen (N) cycling. We used compost at the rate of 20 t ha⁻¹, compost 20 t ha⁻¹ mixed with 10 t ha⁻¹ biochar (compost + biochar) and organo-mineral biochar which also contained 10 t ha⁻¹ biochar. Control samples received neither of the treatments. Compost and compost + biochar increased NH₄⁺ -N concentrations for a short time, mainly due to the release of their NH₄⁺ -N content. Compost + biochar did not alter N cycling of the compost significantly but did significantly increase CO₂ emission compared to control. Compost significantly increased N₂O emission compared to control. Compost + biochar did not significantly change N supply and also did not decrease CO₂ and N₂O emissions compared to compost, suggesting probably higher rates of biochar may be required to be added to the compost to significantly affect compost-induced C and N alteration. The organo-mineral biochar had no effect on N cycling and did not stimulate CO₂ and N₂O emission compared to the control. However, organo-mineral biochar maintained significantly higher dissolved organic carbon (DOC) than compost and compost + biochar from after day 14 to the end of the incubation. Biochar used in organo-mineral biochar had increased organic C adsorption which may become available eventually. However, increased DOC in organo-mineral biochar probably originated from both biochar and chicken manure which was not differentiated in this experiment. Hence, in our experiment, compost, compost + biochar and organo-mineral biochar affected C and N cycling differently mainly due to their different content.