Abstract:

The study investigated the effects of combined application of beet and sugar plant waste sludge and biochar on the fundamental properties and organic carbon components of farmland soil in Northeast China black soil region. Eight treatments were set up for comparison: no material returned to the field (CK₁), 20000 kg/hm² biochar without filter mud (CK₂), 16.67 kg/hm² filter mud without biochar (T₁), 16.67 kg/hm² filter mud with 20000 kg/hm² biochar (T₂), 33.33 kg/hm² filter mud without biochar (T₃), 33.33 kg/hm² filter mud with 20000 kg/hm² biochar (T₄), 50 kg/hm² filter mud without biochar (T₅), and 50 kg/hm² filter mud with 20000 kg/hm² biochar (T₆). Soil total carbon, total organic carbon, easily oxidized organic carbon, water-soluble organic carbon, particulate organic carbon, environmental factors such as alkali-hydrolyzed nitrogen, available phosphorus and available potassium, as well as soil biological activities including urease, phosphatase and sucrase were analyzed to discuss the effects of each treatment on organic carbon components and carbon pool management index. The results indicated that the combined application of filter sludge and biochar significantly increased soil total organic carbon content, easily oxidized organic carbon content and carbon pool management index. The application also affected active carbon components by enhancing available nutrients and enzyme activities which led to an increase in the soil's overall stability. In conclusion, it was found that T₄ treatment, a combination of 33.33 kg/hm² filter sludge with 20000 kg/hm² biochar, yielded the most favorable results in terms of achieving soil carbon sequestration, increasing CPMI content, and improving the stability of soil organic carbons.

Key words: agricultural waste, beet sugar factory waste, filter mud, biochar, soil organic carbon (soc), carbon pool management index (cpmi), soil bioactivity, carbon fixation, organic carbon component