Net Field Global Warming Potential And Greenhouse Gas Intensity In Typical Arid Cropping Systems Of China: A 3-Year Field Measurement From Long-Term Fertilizer Experiments

With the intensification of food production pressure, arid areas have increasingly become one of the key areas for cropland reclamation. However, due to the relatively low indigenous soil organic matter (SOM), it is worth pondering whether the introduction of integrated cropland management measures will affect the soil organic carbon (SOC), greenhouse gases (GHGs) and global warming potential (GWP) in the arid areas. Based on these, a long-term fertilization experiment was used for a three-year GHG study to gain insights into the GHGs and fieldGWP accounting in the western arid region of China. Five treatments, including no fertilizer (CK), inorganic fertilizer (NPK), inorganic fertilizer and straw (NPKS) and two combinations of inorganic fertilizer and manure (NPKM and NPKM+) were selected. Moreover, three crops of cotton, wheat and maize were grown over the three-year period, respectively. Nitrous oxide (N2O) and methane (CH4) concentrations were measured using the static chamber method from April 2012 to July 2014. The results revealed that the SOC of all fertilizer treatments in topsoil (0-20 cm) increased from approximately 27 Mg C ha- 1 in 1990 to 25.5-66 Mg C ha1 in 2014; furthermore, the SOCSR (SOC sequestration rate) values were from -0.035 to 1.70 Mg C ha- 1 yr- 1 in the 25 year experiment. The N2O and CH4 emissions across treatments, crops, and years ranged from 0.2 to 3.8 kg N2O-N ha- 1 yr- 1 and -2.3 to 13.0 kg CH4-C ha- 1 yr- 1, respectively, and the emission factor of CH4 and N2O ranged from -0.1 % to 1.3 % and 0.5 % to 1.0 %, respectively, displaying relatively low GHGs emissions compared with other cropping systems in China. Based on the GHGs and SOCSR results, we found relatively low net field-GWP existed in arid and extremely arid cropping system, especially for the manure amendment treatments, implying the sustainability of certain existing managements in the arid area.