Summary
This study assessed zinc status in 475 soil samples from the Amhara Region of Ethiopia, where zinc deficiency is widespread in human populations. Using isotopic dilution and geochemical modelling, the authors found that phyto-available zinc was severely limited in most samples (median ZnDTPA <0.5 mg kg−1) despite moderate pseudo-total zinc content (median 100 mg kg−1). Soil pH emerged as the dominant control on zinc lability and solubility, explaining 94% of variation in zinc partitioning between solid and solution phases, suggesting that pH management could be a tractable agronomic intervention to improve zinc availability in these soils.
UK applicability
The findings are specific to tropical Ethiopian soils with particular geochemical characteristics and climate; UK soils differ substantially in pH, mineralogy, and organic matter content. However, the methodology (isotopic dilution and WHAM geochemical modelling) is transferable and could inform zinc phyto-availability assessment in UK arable or horticultural contexts where zinc deficiency is documented.
Key measures
Pseudo-total zinc (ZnTot, aqua regia digestion), DTPA-extractable zinc (ZnDTPA), soluble zinc (ZnSoln, 0.01 M Ca(NO3)), isotopically exchangeable zinc (ZnE using enriched 70Zn stable isotope), soil pH, soil geochemical properties; partitioning coefficients and WHAM geochemical model predictions
Outcomes reported
The study measured zinc fractions (pseudo-total, DTPA-extractable, soluble, and isotopically exchangeable) in 475 soil samples from the Amhara Region and used geochemical modelling to assess factors controlling zinc lability and solubility. Widespread phyto-available zinc deficiency was identified, with soluble zinc highly dependent on soil pH.
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