Analysis of Soil Nutrient Content and Carbon Pool Dynamics Under Different Cropping Systems

Understanding the effects of agricultural practices on soil nutrient dynamics is critical for optimizing land management in arid regions. This study analyzed spatial patterns, driving factors, and surface stocks (0–20 cm) of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and their stoichiometric ratios (C:N, C:P, and N:P) across six cropping systems (paddy fields, cotton fields, wheat–maize, orchards, wasteland, and others) in the Aksu region, Northwest China, using 1131 soil samples combined with geostatistical and field survey approaches. Results revealed moderate to low levels of SOC, TN, and TP, and stoichiometric ratios, with moderate spatial autocorrelation for SOC, TN, TP, and C:N but weak dependence for C:P and N:P. Cropping systems significantly influenced soil nutrient distribution: intensive systems (paddy fields and orchards) exhibited the highest SOC (22.31 ± 10.37 t hm⁻ 2 ), TN (2.20 ± 1.07 t hm⁻ 2 ), and TP stocks (peaking at 2.58 t hm⁻ 2 in orchards), whereas extensive systems (cotton fields and wasteland) showed severe nutrient depletion. Soil pH and elevation were key drivers of SOC and TN variability across all systems. The C:N ratio ranked highest in “other systems” (e.g., diversified rotations), while wheat–maize fields displayed elevated C:P and N:P ratios, likely linked to imbalanced fertilization. These findings highlight that sustainable intensification (e.g., paddy and orchard management) enhances soil carbon and nutrient retention, whereas low-input practices exacerbate degradation in arid landscapes. The study provides actionable insights for tailoring land-use strategies to improve soil health and support ecosystem resilience in water-limited agroecosystems.