Nitrogen and carbon losses from dung storage in urban gardens of Niamey, Niger

Abstract

Intensive vegetable production in urban and peri-urban agriculture (UPA) of West African cities is characterized by high nutrient inputs. However, little is known about nitrogen (N) and carbon (C) losses in these systems, in particular during the storage of manure, the main organic fertilizer in these systems. We therefore aimed at quantifying gaseous emissions of ammonia (NH3), nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) as well as leaching losses of C, N, phosphorus (P) and potassium (K) from animal manure stored in vegetable gardens of Niamey, Niger. During a first 3.5-month experiment in the hot dry season, cumulative gaseous N losses, measured with a closed-chamber system, were with 0.11 g kg−1 manure DM highest (P < 0.05) in the uncovered control treatment accounting for 1.8% of total manure N. Nitrogen losses decreased by 72% under plastic sheet roofing and by 50% under roofing + ground rock phosphate (RP) application at 333 g kg−1 manure DM. Carbon losses from manure amounted to 73 g kg−1 DM in the control and to 92 g kg−1 DM and 68 g kg−1 DM under roofing and under roofing + RP, respectively. In a second 3.5-month experiment conducted in the rainy season, C losses from the control were 164 g kg−1 manure DM and reduced to 77 and 65% of the control by roofing and roofing + RP, respectively. Leaching losses during the rainy season were only observed for the unroofed control and averaged 2.1 g C, 0.05 g N, 0.07 g P and 1.8 g K kg−1 manure DM.