Mitigating greenhouse gas emissions through replacement of chemical fertilizer with organic manure in a temperate farmland

Burning crop residues and excessive use of chemical fertilizers results in an enormous waste of biological resources, which further weakens the potential capacity of the agro-ecosystem as a carbon sink. To explore the potential of farmlands acting as a carbon sink without yield losses, we conducted an experiment on a temperate eco-farm in eastern rural China. Crop residues were applied to cattle feed, and the composted cattle manure was returned to cropland with a winter wheat and maize rotation. Four different proportions of fertilizers were designed: 100 % cattle manure, 100 % mineral nitrogen, 75 % cattle manure plus 25 % mineral nitrogen, and 50 % cattle manure plus 50 % mineral nitrogen. Crop yield and greenhouse gas (GHG) emissions were carefully calculated according to the Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories 2006. Our results showed that replacing chemical fertilizer with organic manure significantly decreased the emission of GHGs. Yields of wheat and corn also increased as the soil fertility was improved by the application of cattle manure. Totally replacing chemical fertilizer with organic manure decreased GHG emissions, which reversed the agriculture ecosystem from a carbon source (+2.7 t CO2-eq. hm(-2) year(-1)) to a carbon sink (-8.8 t CO2-eq. hm(-2) year(-1)). Our findings provide useful insights for improving agricultural ecosystems under global change scenarios