Abstract: This study aims to explore the effects of long-term fertilization in arid chestnut soil, to reveal the changes of soil physicochemical and microbial properties under different fertilization schemes. Results would provide basis for reasonable fertilization and scientific evaluation of fertilization effects in the agro-pastoral zone of Inner Mongolia. Based on a long-term rotation fertilization positioning experiment (2004-2019) at Wuchuan Dryland Experimental Station in Inner Mongolia, we examined the effects of different fertilization schemes on the topsoil physicochemical and biological properties of chestnut calcareous soil in the agro-pastoral zone. The results showed that long-term organic manure combined with chemical fertilizer (NPK+OM) and single organic manure (OM) applications significantly reduced soil bulk density and increased soil porosity, while unbalanced fertilization (such as NP, NK, PK, N) and no fertilization (CK) showed an increasing trend in soil bulk density. Compared with CK, the contents of soil organic carbon, total nitrogen, alkaline hydrolysis nitrogen, available phosphorus and available potassium were increased in other treatments. The magnitudes of improvement for soil nutrients were ranked as follows: organic manure combined with chemical fertilizer > organic manure > chemical fertilizer balanced application > chemical fertilizer unbalanced application > no fertilization. In terms of soil microorganisms, soil bacterial abundance increased by 108.36%-118.92%, fungal abundance increased by 27.68%-50.46%, actinomycetic abundance increased by 35.43%-40.25% in NPK+OM. Long-term application of organic manure and balanced application of chemical fertilizer improved soil structure, soil nutrients, and microorganism abundance. In particular, the combination of organic manure and chemical fertilizer is the most effective. The application of reasonable ratio of nitrogen, phosphorus and potassium significantly improved soil quality of arid chestnut soil in the agro-pastoral ecotone, unbalanced fertilization also improved soil properties, while no fertilization significantly degraded soil properties in the long term.

Key words: long-term fertilization, agro-pastoral zone, soil property, soil microorganisms.