Comparative Analysis on Effect of Wheat Straw and Its Biochar Amendment on Net Global Warming Potential Under Wheat-Maize Rotation Ecosystem in the Guanzhong Plain
In order to compare the differences in carbon sequestration and greenhouse gas mitigation between straw and straw-derived biochar amendment, a field experiment was conducted with simultaneous measurement of carbon dioxide (CO_2), methane (CH_4) and nitrous oxide (N_2O) emissions, crop yield, soil organic carbon (SOC) content and net global warming potential (NGWP) in a wheat-maize rotation cropping system from the loess plateau of China. Five treatments were included:control (no straw incorporation, no straw-derived biochar amendment and no fertilization, CK), fertilization (no straw incorporation and no straw-derived biochar amendment, F), straw with fertilization (wheat straw incorporated at 8 t·hm~(-2), FS), low straw-derived biochar (8 t·hm~(-2)) with fertilization (FBlow) and high straw-derived biochar (16 t·hm~(-2)) with fertilization (FBhigh). Wheat yield increased by 30.9%, 66.3% and 36.6% under FS, FBlow and FBhigh treatment, as compared to the F treatment, respectively. However, maize yield decreased by 14.1%, 18.0% and 24.6% under FS, CK and FBhigh treatment as compared to the F treatment, respectively. There was no significant difference between FBlow and F treatment. Annual CO_2 emission increased by 60.2% under FS treatment, but decreased by 14.4% under FBhigh treatment as compared to the F treatment, respectively. Annual N_2O emission decreased by 27.6% and 38.7% under FBlow and FBhigh treatment as compared to the F treatment, respectively. However, no significant difference was observed under straw application. Overall, the NGWP decreased by 24.13 and 58.44 t·hm~(-2) under FBlow and FBhigh treatment as compared to the F treatment, respectively. And the NGHGI decreased by 1.78 and 5.06 t·t~(-1) under FBlow and FBhigh treatment as compared to the F treatment, respectively. In summary, we conclude that the fertilization with 16 t·hm~(-2) biochar amendment can be used as an effective management to improve the crop yield and reduce the net global warming potential under the wheat-maize rotation system.