Responses of carbon, nitrogen and phosphorus to two consecutive drying–rewetting cycles in soils

Summary

This laboratory study examined how consecutive drying-rewetting cycles affect carbon, nitrogen, and phosphorus dynamics in soil over 14 days, comparing drying-rewetting treatments with continuously moist controls. During the first drying period, drying-rewetting samples exhibited significant increases in extractable ammonium, oxidised nitrogen, and bicarbonate-extractable phosphorus; rewetting after the first drying event induced a substantial spike in CO₂ flux (55.4 µg C g⁻¹ d⁻¹). The findings suggest that changing moisture patterns under future climate scenarios will have measurable impacts on soil microbial biomass and nutrient availability, though distinguishing between microbial and physical perturbation effects remains challenging.

UK applicability

The findings are directly relevant to UK soil management, given projected increases in extreme precipitation and drought events under climate change. UK agricultural soils are likely to experience more frequent drying-rewetting cycles, making understanding of these nutrient dynamics important for maintaining soil health and predicting nutrient availability to crops.

Key measures

Extractable ammonium, total oxidised nitrogen, bicarbonate-extractable phosphorus, microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), CO₂ flux (µg C g⁻¹ d⁻¹), N₂O emissions, soil water-holding capacity

Outcomes reported

The study measured short-term responses of extractable nitrogen, phosphorus, and microbial biomass carbon and phosphorus to two consecutive drying-rewetting cycles in soil over a 14-day incubation period, alongside associated CO₂ and N₂O emissions. Changes in nutrient availability and microbial biomass were tracked across moisture regimes to understand soil behaviour under varying water conditions.

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