Interactive effects of straw-derived biochar and N fertilization on soil C storage and rice productivity in rice paddies of Northeast China.

Impacts of biochar on greenhouse gas emissions and C sequestration in agricultural soils have been considered as the key to mitigate climate change. There is limited knowledge regarding the effects of rice straw-derived biochar and interaction with N fertilization on soil C sequestration and rice productivity in fertile paddy fields. A 2-year (2013 and 2014) consecutive field trial was performed using straw treatment (5.05 t ha − 1 ) and biochar amendment (0, 1.78, 14.8 and 29.6 t ha − 1 ) with or without urea application in a rice paddy in Northeast China. A super high yielding rice variety ( Oryza sativa L. subsp. Japonica cv. ‘Shennong 265’) was cultivated with permanent flooding. Results showed that biochar amendments significantly decreased CH 4 emissions relative to straw treatment irrespective of N fertilization, especially in N-fertilized soils with 1.78 t ha − 1 biochar. There were no differences in CO 2 emissions with respect to biochar amendments, except for 14.8 t ha − 1 biochar with N fertilization. Straw treatment had the highest global warming potential over a 100-year time frame, which was nearly 1.5 times that of 14.8 t ha − 1 biochar amendment without N fertilization. Biochar addition increased total soil C by up to 5.75 mg g − 1 and 11.69 mg g − 1 (with 14.8 and 29.6 t ha − 1 biochar, respectively), whereas straw incorporation increased this value by only 3.92 mg g − 1 . The aboveground biomass of rice in biochar-amended soils increased to varying degrees compared with that in straw-treated soils. However, biochar application had no effects on rice yield, regardless of N fertilization. This study indicated that transforming straw to biochar was more stabilized and more suitable to mitigate greenhouse gas emissions and increase C storage in agriculture soils in Northeast China. [ABSTRACT FROM AUTHOR]