Comparison of tracking and fixed photovoltaic systems for soil quality improvement in desert: A 5-year field study

Deserts offer abundant sunlight and space ideal for photovoltaic (PV) energy; however, the long-term impact of PV systems on desert soil quality remains unclear. This 5-year Kubuqi Desert study compared tracking (oblique/flat single-axis) and fixed-tilt (adjustable/fixed-angle) PV systems to uncovered control plots (with identical land preparation). Compared to the control, the soil moisture and bulk density remained unchanged overall but varied significantly beneath and between the panels under the fixed systems. Both PV types significantly increased soil organic carbon, with tracking systems also boosting available nitrogen and carbon (β-glucosidase) and nitrogen-cycling (leucine aminopeptidase) enzyme activities. Conversely, fixed systems significantly decreased soil calcium carbonate, total phosphorus, available phosphorus, and available potassium. Soil pH was significantly lower under the tracking system than under the fixed system. Partial least squares discriminant analysis distinguished the oblique single-axis tracking system, linking it to lower pH and enhanced enzyme-driven nutrient cycling, which was supported by Mantel tests and Pearson correlations. Consequently, both the oblique and flat single-axis tracking systems significantly increased the soil quality index compared to that of the fixed systems and control. These findings indicate that tracking PV systems create more uniform soil conditions and drive positive changes in soil chemical and biological properties, thereby improving desert soil quality more effectively than fixed systems do.