Quantifying the Effects of Compost and Biochar Over a 3-Year Crop Rotation Using Site-Specific Soil Health Equation
Karimi, Z.. 2026.
Abstract
Soil health is a critical determinant of sustainable crop production, yet the short- and long-term impacts of
organic and synthetic amendments on soil properties remain incompletely understood on Prairie Luvisols
under agricultural management. This study evaluated the effects of compost, synthetic fertilizer, and
blended organic-synthetic amendments on soil health and crop productivity over a three-year rotation of
canola (2022), wheat (2023), and faba bean (2024) on a Dark Gray Luvisol. Soil chemical, biological, and
physical properties were measured, including macronutrients, micronutrients, total carbon, total nitrogen,
pH, electrical conductivity, organic matter, autoclaved-citrate extractable protein, permanganate-oxidizable
carbon, and microbial respiration. Crop yields were recorded and moisture-adjusted. Principal Component
Analysis identified five critical indicators, zinc, total nitrogen, phosphorus, nitrate-nitrogen, and boron, that
were normalized using cumulative distribution function scaling to generate a Site-Specific Soil Health
Index (SPSHI). Short-term soil variability in SPSHI was primarily driven by chemical indicators, while
biological indicators increased gradually over time, reflecting cumulative improvements in microbial activity and organic matter. Across three years, the Compost Synthetic Fertilizer treatment consistently
ranked among the highest for both SPSHI and yield, demonstrating that blended amendments can balance
immediate crop productivity with the promotion of soil health. Yield responses were crop-specific:
Synthetic Fertilizer treatments maximized canola and wheat yields, whereas compost treatments performed
competitively under faba bean, suggesting benefits of organic inputs and nitrogen-fixation over time.
Correlations between SPSHI and yield were positive and became strengthened over time, indicating that
improvements in soil health contribute progressively to crop productivity, although the relationships were
weak in magnitude. Overall, this study provides a practical framework for assessing soil health on Luvisols
being farmed in Alberta, highlights the complementary roles of chemical and biological indicators, and
underscores the value of blended organic-synthetic management strategies for achieving both short-term
productivity and long-term soil function.
