Abstract
A laboratory microcosm incubation was conducted to study the influence of mixed cowpea-maize residues on N2O emission and N mineralization in a tropical acrisol. The soils were incorporated with different ratios of cowpea:maize mixtures on weight basis: 100:0, 75:25, 50:50, 25:75 and 0:100, and a control treatment in which there was no residue incorporation. The results show that N2O and CO2 emissions were higher in the sole cowpea treatment (100:0) than the sole maize treatment (0:100) and the control. However, cowpea-maize residue mixtures increased the proportion of N lost as N2O compared to the sole treatments. This interactive effect was highest in the 75:25 treatment. The 50:50 treatment showed moderate N2O emission compared to the 100:0, 75:25 and 25:75 treatments but with corresponding steady N mineralization and appreciable mineral N concentration. It is concluded that mixing cowpea-maize residues might increase the proportion of N lost as N2O in a tropical acrisol. However, compared to the other residue mixture treatments, mixing cowpea-maize residues in equal proportions on weight basis might offer a path to reducing N2O emissions while maintaining a steady N mineralization without risking good N supply in acrisols. The study therefore offers potential for mitigating greenhouse gas emissions while maintaining soil fertility in tropical acrisols. However, further studies under both laboratory and field conditions will be required to verify and validate this claim.
Highlights
Agro-ecological research has recently become focused on economically-viable soil fertility management and on environmentally-friendly systems [1]
It is believed that 90% of global anthropogenic N2O emissions originate from soils [3] and 6.3 Tg of N2O-N is emitted from agricultural systems, representing more than half of anthropogenic N2O emissions [4]
The soil was pre-incubated at 45% WFPS and 25 °C for 7 days prior to addition of the residues to re-initiate microbial activity after 1 year of cold storage (−4 °C), and to minimize changes in soil water filled pore space (WFPS) at the start of the experiment
Summary
Agro-ecological research has recently become focused on economically-viable soil fertility management and on environmentally-friendly systems [1]. It is believed that 90% of global anthropogenic N2O emissions originate from soils [3] and 6.3 Tg of N2O-N is emitted from agricultural systems, representing more than half of anthropogenic N2O emissions [4]. Both nitrification and denitrification produce N2O as intermediate product from organic and inorganic N sources in soils [5]. In Ghana, agriculture accounts for 65% of the 3.07 Gg N2O emissions (1994 baseline year), while biomass burning contributes 27% [7]
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