Bioavailability of macro‐ and micro‐nutrients chemically extracted in acidic soils for wheat

Abstract

Background: Chemical methods allowing a single soil extraction followed by multi‐elemental simultaneous measurement by ICP‐OES are increasingly used to predict plant uptake; however, calibration results against crop response are scarce and contradictory.Aims: Our aims were to evaluate the efficacy of five extractants to predict nutrient uptake by a greenhouse wheat crop, as well as the influence of soil properties on nutrient concentrations in soil extracts and wheat plants.Methods: Unlike other calibration studies, we monitored the pre‐seeding to post‐harvesting changes in soil available Ca, K, Mg, Cu, Fe, Mn, Zn, and Al. We extracted 14 acidic soils (C content: 47–114 g kg−1) with two traditional (AA: ammonium acetate; DTPA: diethylenetriamine‐pentaacetic acid) and three multi‐element extractants (AB‐DTPA: ammonium bicarbonate‐DTPA; Mehlich‐3; AA‐DTPA: ammonium acetate‐DTPA).Results: Relationships between bioavailable and chemically extractable elements were strong for K (R2 = 0.776 to R2 = 0.882; p < 0.001) and Zn (R2 = 0.663 to R2 = 0.721; p < 0.001), especially for AB‐DTPA and AA‐DTPA. Multiple regressions including also soil properties can predict wheat‐Ca (Feoxihydroxides, clay and CaAB‐DTPA; R2 = 0.656; p < 0.001) and wheat‐Cu [Aloxihydroxides and either CuAB‐DTPA (R2 = 0.515; p < 0.01) or CuAA‐DTPA (R2 = 0.472; p < 0.01)]. Pre‐seeding to post‐harvesting changes in KAA‐DTPA and KAB‐DTPA were strongly related with K uptake by wheat (R2 = 0.927 and R2 = 0.949, respectively; p < 0.001); similarly, for wheat‐Zn the best relationships were with ZnMehlich‐3 and ZnAA‐DTPA (R2 = 0.654 and R2 = 0.757, respectively; p < 0.001).Conclusion: Consequently, chemical extractants alone can adequately predict K and Zn bio‐availability, and combined with some soil properties can predict wheat uptake of Ca and Cu, but not that of other nutrients.