Natural Potassium (K) Isotope Fractionation during Corn Growth and Quantification of K Fertilizer Recovery Efficiency Using Stable K Isotope Labeling

Summary

This controlled pot experiment demonstrates the application of high-precision stable potassium isotope analysis (δ41K) as a novel tracer method to quantify fertiliser K uptake in corn and elucidate soil–plant K cycling. Using 41K-enriched fertiliser tracers at three application rates (50–200 mg K kg−1 soil), the authors report apparent fertiliser recovery efficiencies of 59–81% and identify a mass-dependent isotopic fractionation signature (−0.37‰) favouring light K isotope uptake by plants. The study suggests that isotopic approaches provide clearer mechanistic insight into K bioavailability dynamics than concentration-based methods alone, which underestimated utilisation at low K doses and overestimated it at high doses.

UK applicability

The methodology is directly applicable to UK agricultural contexts, where improving potassium fertiliser use efficiency is an economic and environmental priority. Whilst developed in a controlled pot setting, the isotopic fractionation and recovery patterns identified may inform future field studies on K cycling in UK cereal production systems, particularly where soil type and management practices influence K availability.

Key measures

δ41K values (stable K isotope ratios); fertiliser recovery efficiency (%); mass-dependent K isotope fractionation (‰ in 41K/39K); shoot and soil K concentration

Outcomes reported

The study quantified potassium fertiliser uptake by corn using stable isotope labelling, measuring apparent fertiliser recovery efficiency and demonstrating that isotopic fractionation patterns distinguish between native soil K and applied fertiliser sources. The research revealed that conventional K concentration-based methods systematically misestimate fertiliser utilisation across different application rates.

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