Carbon dioxide and gaseous nitrogen emissions from biochar‐amended soils under wastewater irrigated urban vegetable production of Burkina Faso and Ghana

Urban Farm DB summary

To quantify carbon and nitrogen losses in urban and peri-urban agriculture soils in West Africa, this study measured CO2-C, N2O-N, and NH3-N fluxes from irrigated fields in Ouagadougou, Burkina Faso, and Tamale, Ghana, under different fertilization and (waste)water regimes. Compared with unamended controls, fertilizer application increased average cumulative CO2-C emissions by 103% over eight cropping cycles in Ouagadougou and by 42% over seven cropping cycles in Tamale. Total emissions across all cropping cycles reached 14 t C/ha in Ouagadougou — 73% of the carbon applied as organic fertilizer over two years at that site — and 9 t C/ha in Tamale. Fertilizer application increased N2O-N emissions in Ouagadougou by 37-360% across cropping cycles and NH3-N losses by an average of 670%, but had no significant effect on N2O-N losses in Tamale. Wastewater irrigation did not significantly raise CO2-C emissions in Ouagadougou, but in Tamale CO2-C emissions were 71% higher on wastewater plots (1.6 t C/ha) than on controls (0.9 t C/ha); wastewater had no significant effect on N2O-N or NH3-N emissions at either site. Biochar did not affect N2O-N or NH3-N losses but could help reduce CO2-C emissions from urban garden soils.