Greenhouse gas emission and nitrogen availability in improved fallow farming systems in Nyabeda, Western Kenya

Abstract

Nitrous oxide, carbon dioxide and methane emissions were measured from different agricultural systems in Nyabeda, Siaya District in western Kenya. These systems were Tephrosia candida, Crotalaria paulina, natural fallows, and continuously cropped fertilized and unfertilized maize (Zea mays). Gaseous emissions are of particular concern due to their role in global warming. Global warming increases the frequencies of extreme disasters e.g. floods, droughts and storms that negatively affect agriculture and increases skin cancer and other health problems. Total N2O emissions measured over 99 days were higher (P<0.01) from Tephrosia (584 g N2O-N ha-1) and Crotalaria (554 g N2O-N ha-1) than from unfertilized maize and natural fallow treatments. Crotalaria and fertilized maize emitted 257 and 192 g CH4-Cha-1 respectively and were significantly higher (P<0.01) than from other treatments. Crotalaria still emitted higher total CO2 (2967 kg CO2 –Cha-1) than the other treatments. Fluxes of N2O, CO2 and CH4 followed a similar trend. The findings of this study will be important in developing practices that increase N-use efficiency and reduce greenhouse gas emissions. Despite increased gas emissions from improved fallows, N availability was high following incorporation of their residues. N availability in all the treatments declined over time during the cropping season indicating that the soil N capital is not adequate.