Effects of organic and mineral fertilizer nitrogen on greenhouse gas emissions and plant-captured carbon under maize cropping in Zimbabwe uri icon


  • Optimizing a three-way pact comprisingcrop yields, fertility inputs and greenhouse gases mayminimize the contribution of croplands to globalwarming. Fluxes of N2O, CO2 and CH4 from soilwere measured under maize (Zea mays L.) grownusing 0, 60 and 120 kg N hm-2 as NH4NO3-N andcomposted manure-N in three seasons on clay(Chromic luvisol) and sandy loam (Haplic lixisol)soils in Zimbabwe. The fluxes were measured usingthe static chamber methodology involving gas chromatographyfor ample air analysis. Over an average of122 days we estimated emissions of 0.1 to 0.5 kgN2O-N hm?2, 711 to 1574 kg CO2-C hm?2 and?2.6 to5.8 kg CH4-C hm?2 from six treatments during seasonII with the highest fluxes. The posed hypothesis thatcomposted manure-N may be better placed as amitigation option against soil emissions of GHG thanmineral fertilizer-N was largely supported by N2Ofluxes during the wet period of the year, but with highlevel of uncertainty. Nitrogen addition might havestimulated both emissions and consumption of CH4but the sink or source strength depended highly onsoil water content. We concluded that the applicationof mineral-N and manure input may play an importantrole with reference to global warming provided theseason can support substantial crop productivity thatmay reduce the amount of N2O loss per unit yield.Confidence in fluxes response to agricultural managementis still low due to sporadic measurementsand limited observations from the southern Africanregion

publication date

  • 2011