Effects Of Biochar On Stability Of Soil Aggregates And Active Organic Carbon In Black Soil

As a valuable land resource,the black soil in Northeast China is fertile and suitable for crop growth.It is an important guarantee for increasing grain production and income in Northeast China.However,with the increase of reclamation years,the black soil is degraded seriously,soil and water loss,and soil layer thinned.The decline of organic matter affects the stable yield and sustainable development of local agriculture.Biochar is a carbon rich material with dense porosity,high specific surface area and high bio-chemical stability,It is important for improving soil organic matter content and soil physical and chemical properties.so The objective of this study was carried out to investigated the effects of biochar addition on the distribution of soil aggregates carbon and active organic carbon in the black soil.Biochar was added to a maize field at five rates(30t·hm~2(C4),15t·hm~2(C3),3t·hm~2(C2),1.5 t·hm~2(C1)and 0t·hm~2(CK))planing time before.The soil samples were collected from two different profiles(0-20 cm and 20-40 cm)in the planing time and harvest time.Soil samples were fractionated into different aggregate sizes(>2 mm,2-0.25 mm,0.25-0.053 mm and <0.053 mm)using the wet sieving method,and then the contents of soil organic carbon and active organic carbon in different water-stable aggregates were measured.Correlations of contents of total organic carbon(TOC)and dissolved organic carbon(DOC),Hot water extractable carbon(HWC)acid-hydrolyzed organic carbon Ⅰ,Ⅱ(AHC Ⅰ,AHC Ⅱ)and readily oxidized organic carbon(ROOC)were also analyzed and to It aimed at providing certain scientific basis for comprehensive understanding of soil eco-environmental effect of biochar on promoting black soil qualities and agricultural application by quantifying aggregate characteristics and distributions of soil carbon and active organic carbon following the application of biochar.The main results are as follows:1.Biochar significantly increased soil water content during the harvest period and reduced soil bulk density and soil specific gravity and increased soil porosity in 0-20 cm soil layers,There was no significant difference in soil bulk density,soil specific gravity,and soil porosity on 20-40 cm soil layers.2.Biochar significantly increased the content of aggregates >2 mm and reduced the content of <0.053 mm aggregates,while significantly reducing the content of 0.25-0.053 mm aggregates in 0-20 cm soil layers.Biochar significantly increased the mean weight diameter(MWD)and the contents of >0.25 mm water-stable aggregates and the geometric mean diameter(GMD)of 0-20 cm soil layers.3.Biochar significantly increased TOC,AHC Ⅰ,Ⅱ and ROOC in 0-20 cm soil layers and TOC,DOC,AHC Ⅰ and ROOC in the 20-40 cm soil layer during the harvesting period,the HWC is increased 3.71%-27.61%,whlie DOC is reduced in 0-20 cm soil layer.There was a significant positive correlation between TOC and HWC,AHC Ⅰ,Ⅱ and ROOC.4.Biochar significantly increased TOC,AHC II and ROOC content in different grain-size soil aggregates in 0-20 cm soil layer and harvest period of 20-40 cm soil layer,and significantly increased the content of AHC Ⅰ and HWC of >2 mm,2-0.25 mm and 0.25-0.053 mm aggregates in harvest time.Biochar significantly reduced the DOC content of soil aggregates at different grain sizes in the 0-20 cm soil layer during harvest,but significantly increased the DOC content of soil aggregates at different grain sizes in 20-40 cm soil layers.5.Biochar improves the contribution of organic carbon and active organic carbon of >2 mm aggregates in 0-20 cm soil layer.The contribution of TOC,HWC and ROOC of 0.25-0.053 mm and <0.053 mm aggregates in the 0-20 cm soil layer were reduced,and the contribution of TOC and AHC Ⅰ and HWC of 0.25-0.053 mm aggregates in the 20-40 cm soil layer at the harvesting stage were increased.