Soil profile health in the Palouse soil series: Carbon, nitrogen, nutrients, and aggregates

Summary

This field study examined how no-till and conventional tillage management affect soil health indicators across the full profile (0–85 cm depth) in dryland wheat systems in the Palouse watershed. No-till sites showed greater surface carbon, nitrogen, and aggregate stability, but paradoxically lower total carbon and nitrogen in deeper layers, suggesting that tillage effects on soil health are depth-dependent and cannot be assessed reliably using surface sampling alone. Climate effects, mediated through mean annual precipitation across the 460–660 mm gradient, independently modulated carbon mineralisation and nutrient availability in both surface and subsurface soils.

UK applicability

The findings are moderately relevant to UK dryland cereal systems, particularly in lower-rainfall regions of eastern England, though the Palouse's lower precipitation and different soil parent materials limit direct extrapolation. The emphasis on evaluating soil health beyond 30 cm depth is applicable to UK practice, where subsurface soil compaction and nutrient stratification are also concerns under conservation agriculture.

Key measures

Total carbon and nitrogen, permanganate oxidizable carbon, hot-water and cold-water extractable carbon and nitrogen, soil moisture, mean weight diameter of soil aggregates, soil pH, nitrate and ammonium concentrations, mineralizable soil carbon, and autoclaved-citrate extractable protein at multiple 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 (soil aggregate stability) health indicators across 0–85 cm depth profiles under no-till versus conventional tillage management. Results demonstrated depth-dependent and climate-modulated responses of soil health indicators to tillage practice in dryland wheat systems.

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