Biochar Addition with Water and Fertilization Reduction Increases Soil Aggregate Stability of 0–60 cm Soil Layer on Greenhouse Eggplant in Mollisols

Abstract

Biochar application affects the soil organic carbon (SOC) content and distribution, which is relevant to facility agriculture and soil aggregates. However, how the fertilization management of facility agriculture affects the SOC content and aggregate stability at different soil depths in Mollisols is unclear. Intended to provide a basis for developing a reasonable fertilizer amount when adding biochar, the facility vegetable eggplant in Northeast China was used to explore the effects of biochar addition on the distribution and SOC content of whole soils and the organic carbon (OC) content of aggregates of each size in the profile (0–100 cm) of Mollisols. Three treatments were set up: WF (conventional application amounts of water and fertilizer), WFB (conventional application amounts of water and fertilizer and added biochar), and 80%W80%FB (20% water reduction and 20% fertilizer reduction and added biochar). The results demonstrated that the 80%W80%FB treatment significantly increased the SOC content by 56.1% and 34.0% in whole soils at a 0–20 cm soil depth compared to WF and WFB treatments, respectively. Simultaneously, compared with WF and WFB treatments, the significant increase in the OC content of 1–0.25 mm sized aggregates of 81.4–130.2% and 4.3–10.1% and the enhanced proportion of >2 mm sized aggregates of 0.22–16.15- and 0.33–0.83-fold both improved aggregate stability in the 0–20 cm soil layer under the 80%W80%FB treatment, which was proven to result in 32.6% and 30.6% increments in the weight diameter (MWD) value. Therefore, biochar addition with water and fertilizer reductions increases surface soil aggregate stability for greenhouse eggplants in Mollisols.