Relief variation influence on soil moisture in agrofields in Northern Kazakhstan

Аннотация

Background and Aim. As a result of the Soviet land resource planning system, large agrofields in Northern Kazakhstan have historically been delineated by administrative boundaries rather than relief characteristics, which can impact soil moisture heterogeneity under semi-arid conditions. This study aims to quantify how micro-relief variability controls soil moisture distribution within a representative chernozem field using UAV-derived terrain data and in-situ soil moisture telemetry.
Materials and Methods.The study was conducted in test Field No. 64 (440 ha), Kostanay region, Kazakhstan. The high-resolution Digital Terrain Models were generated from UAV photogrammetry (Mavic 2 Pro; August 2024) and used to characterize elevation gradients. The six Sentek Drill & Drop probes (0-60 cm, 10 cm intervals) were installed within the elevation range and recorded volumetric water content at 30-minute intervals from May-September 2025, the telemetry from sensors was qualitycontrolled and aggregated to monthly means. Elevation effects were assessed to determine relationships for each month and depth horizon using Pearson and Spearman correlations and ordinary least-squares regression (VWC = a + b•Elevation).
Results. Despite a small elevation span (~3 m at probe locations), monthly mean soil moisture exhibited consistent moderate associations with elevation, particularly in the early season and deeper horizons. Statistically significant Pearson relationships (p < 0.05) were observed for May at 10-20 cm (r = -0.95; b = -3.03% VWC per m; R² = 0.90), 20-30 cm (r = -0.91; b = -1.87% per m; R² = 0.83), and 50-60 cm (r = -0.86; b = -2.08% per m; R² = 0.73). In June, significant effects persisted at 40-50 cm (r = -0.86; b = -1.47% per m; R² = 0.74) and 50-60 cm (r = -0.93; b = -2.67% per m; R² = 0.86), and in July at 50-60 cm (r = -0.85; b = -1.82% per m; R2 = 0.72), indicating systematically wetter conditions at lower microtopographic positions.
Conclusion. Integrating UAV-derived terrain metrics with depth-resolved soil moisture telemetry enables detection of meaningful micro-topographic controls on root-zone water availability within large steppe agrofields. The identified elevation–moisture gradients can support within-field zoning, targeted water-conservation practices, and more robust interpretation of remote-sensing soil moisture products in Northern Kazakhstan.