[Effect of Chicken Manure Biochar on Lime Soil Aggregates and Its Stabilization Mechanism]

Biochar, as a new type of environmental functional material with ecological restoration functions, has broad applications in soil quality improvement and remediation. Similar to biochar prepared from plants, chicken manure biochar has the characteristics of well-developed pore structure, large specific surface area, and rich plant nutrients and has received widespread attention in the fields of environment and agriculture. In this study, a short-term soil cultivation experiment was carried out by adding chicken manure （JF） biochars prepared by pyrolysis at 400℃ and 600℃ with 1% and 2% doses to lime soil for 42 days. As such, five treatments were set up, including a control group （CK） without biochar addition, 1%-JF400, 1%-JF600, 2%-JF400, and 2%-JF600. The effects of pyrolysis temperature and biochar doses on the distribution and stability of aggregates in the lime soil, as well as the relevant mechanisms, were studied. The results showed that the content and stability of water-stable macro-aggregates in the lime soil were significantly improved by the addition of different chicken manure biochars, with water-stable macro-aggregates （R_0.25） increasing by 42%-101.9%, average weight diameter （MWD） increasing by 14.3%-57.1%, and geometric average diameter （GWD） increasing to 1.5-4 times of CK. 1%-JF400 enhanced the bridging effect of calcium ions and strengthened the binding of organic matter with amorphous iron, aluminum, and silicate by enhancing the accumulation of organic carbon in soil aggregates at all levels （14.0%-99.2%）, increasing the ratio of C=C/-CH （144.4%-633.3%）, and increasing the relative abundance of Al-O and Ca-O bonds in large aggregates （26.7%-54.5%） and Fe-O and Ca-O bonds （71.0%-116.7%） in small aggregates. The formation and stabilization of soil aggregates were then promoted. In addition, 1%-JF400 also increased the light content （39.8%） and slightly decreased the recombination content （2.6%） of the soil aggregates but significantly increased the contents of Ca-SOC （117.2%） and Fe/Al-SOC （17.1%） in the recombinant components. This promoted the formation of organic-inorganic complexes in the soil and improved the structure of soil aggregates. The conclusions of this study provide a theoretical basis and application guidance for the land use of chicken manure biochar.