To quantify carbon (C) and nitrogen (N) losses in soils of West African urban and peri‐urban agriculture (UPA) we measured fluxes of CO₂‐C, N₂O‐N, and NH₃‐N from irrigated fields in Ouagadougou, Burkina Faso, and Tamale, Ghana, under different fertilization and (waste‐)water regimes. Compared with the unamended control, application of fertilizers increased average cumulative CO₂‐C emissions during eight cropping cycles in Ouagadougou by 103% and during seven cropping cycles in Tamale by 42%. Calculated total emissions measured across all cropping cycles reached 14 t C ha⁻¹ in Ouagadougou, accounting for 73% of the C applied as organic fertilizer over a period of two years at this site, and 9 t C ha⁻¹ in Tamale. Compared with unamended control plots, fertilizer application increased N₂O‐N emissions in Ouagadougou during different cropping cycles, ranging from 37 to 360%, while average NH₃‐N losses increased by 670%. Fertilizer application had no significant effects on N₂O‐N losses in Tamale. While wastewater irrigation did not significantly enhance CO₂‐C emissions in Ouagadougou, average CO₂‐C emissions in Tamale were 71% (1.6 t C ha⁻¹) higher on wastewater plots compared with those of the control (0.9 t C ha⁻¹). However, no significant effects of wastewater on N₂O‐N and NH₃‐N emissions were observed at either location. Although biochar did not affect N₂O‐N and NH₃‐N losses, the addition of biochar could contribute to reducing CO₂‐C emissions from urban garden soils. When related to crop production, CO₂‐C emissions were higher on control than on fertilized plots, but this was not the case for absolute CO₂‐C emissions.

中文翻译：

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布基纳法索和加纳污水灌溉的城市蔬菜生产下生物炭改良过的土壤中的二氧化碳和气态氮排放

为了量化西非城市农业和近郊农业（UPA）土壤中的碳（C）和氮（N）损失，我们测量了灌溉农田中CO ₂ ‐C，N ₂ O‐N和NH ₃ ‐N的通量。布基纳法索的瓦加杜古和加纳的塔马莱，处于不同的施肥和（废物）水制度下。与未经修正的控制相比，肥料的使用使瓦加杜古的八个种植周期的平均累积CO ₂ -C排放增加了103％，而塔马莱的七个种植周期的平均累积CO ₂ -C排放则增加了42％。在瓦加杜古，整个种植周期测得的总排放量达到14 t C ha ^-1，占该地点两年内用作有机肥料的碳排放量的73％和9 t C ha在Tamale中为^-1。与未修正的对照样地相比，在不同的种植周期内，化肥的施用增加了瓦加杜古的N ₂ O-N排放量，范围从37％到360％，而平均NH ₃ -N损失增加了670％。施肥对玉米粉虱的N ₂ O-N损失没有显着影响。而废水灌溉没有显著提高CO ₂在瓦加杜古-C排放，平均CO ₂在Tamale -C排放分别为71％（1.6吨碳公顷^-1）废水地块更高与对照（0.9吨碳公顷相比^{- 1}）。但是，废水对N ₂ O-N和NH _3的影响不明显在任一地点均观测到N排放。尽管生物炭不影响N ₂ O‐N和NH ₃ ‐N的损失，但添加生物炭可有助于减少城市花园土壤中的CO _2‐ C排放。与作物生产相关时，控制下的CO _2- C排放量高于施肥地，但绝对CO _2- C排放情况并非如此。