Fertility changes and comprehensive quality evaluation of dryland red soil under different long-term fertilization patterns.

Analyzing the effects of long-term fertilization treatments on dryland red soil fertility and identifying optimal fertilization regimes for soil amelioration are of great significance for enhancing soil fertility and crop yield. Based on a 37-year fertilization experiment (1986-2023) in Jiangxi Province, we examined the impacts of six treatments, no fertilization (CK), nitrogen-only (N), chemical fertilizer (NPK), double-dose chemical fertilizer (2NPK), organic manure (OM), and combined chemical-organic fertilization (NPKM) on soil physical, chemical, and biological properties, maize yield, and comprehensively assessed soil fertility using the integrated fertility index (IFI). The results showed that long-term organic fertilization (OM and NPKM) significantly increased soil pH, macroaggregate content, soil organic matter, total nitrogen, total phosphorus, available nutrients, and activities of catalase, sucrase, glucosidase cellulase, urease, and acid phosphatase. Long-term chemical fertilization (NPK and 2NPK) showed weak improvements in these parameters, while long-term application of nitrogen-only (N) reduced soil pH, organic matter, total nitrogen, total phosphorus, available nutrients content, and the activities of catalase, sucrase, and glucosidase. NPK, 2NPK, OM and NPKM treatments significantly increased maize yield relative to CK by 847.6%, 712.7%, 716.3%, and 1162.7% respectively. Maize yield exhibited significant positive correlations with soil macroaggregates, pH, total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen, available phosphorus contents, and activities of all the tested enzymes. The IFI values derived from both minimum and full datasets consistently ranked: NPKM>OM>2NPK>NPK>CK>N, with a significant positive correlation between datasets. Thus, long-term combined chemical-organic fertilization optimally could enhance dryland red soil fertility and maize yield. Alkali-hydrolyzable nitrogen, total phosphorus, pH, and catalase were key indicators for evaluating soil fertility.