Summary
This field study examined how no-till and conventional tillage practices, combined with a precipitation gradient (460–660 mm mean annual), affected soil health indicators to 85 cm depth in the Palouse soil series of the Pacific Northwest. No-till sites showed higher carbon and nitrogen stocks and aggregate stability in surface soils but lower subsurface reserves and mineralizable fractions compared to conventional tillage, whilst higher-precipitation sites exhibited greater mineralizable carbon but lower total carbon at depth. The findings underscore the necessity of evaluating soil health across multiple depths and climatic contexts to understand subsurface conditions supporting deep root systems in dryland wheat.
UK applicability
The study's focus on dryland cereal systems and the mechanistic examination of tillage effects on soil health indicators have relevance to UK arable practices, particularly in lower-rainfall regions and where conservation agriculture adoption is considered. However, UK soils and climatic conditions differ substantially from the Palouse region; UK rainfall patterns and soil series require context-specific evaluation of these findings.
Key measures
Total carbon (TC), total nitrogen (TN), permanganate oxidisable carbon, hot-water and cold-water extractable carbon and nitrogen, soil moisture, mean weight diameter (MWD) of aggregates, soil pH, nitrate (NO₃⁻), ammonium (NH₄⁺), mineralizable soil carbon (MINC), autoclaved-citrate extractable (ACE) protein, measured at multiple soil depths (0–5, 5–10, 10–29, 29–59, 59–85 cm)
Outcomes reported
The study measured soil chemical (nutrients, pH), biological (carbon and nitrogen fractions), and physical (aggregate stability) health indicators across soil depths (0–85 cm) in Palouse soil series under no-till versus conventional tillage with varying precipitation. It quantified how tillage and climate gradient conditions affected subsurface soil health in dryland wheat cropping systems.
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