Comparison and modelling of extraction methods to assess agronomic effectiveness of fertilizer zinc

Abstract

Total Zn in fertilizer is a poor predictor of Zn availability in granular fertilizers. In this study, we compared different extraction methods using Zn fertilizers for which the agronomic effectiveness had previously been determined. Sixteen fertilizers were extracted by eight different procedures using five extractant solutions: water, 1 M ammonium acetate (pH 7.0), 74 mM EDTA (pH 7.0), 5 mM DTPA + 0.1 M MES (pH 6.2), and 0.12 M bis‐tris (pH 6). Modelling of Zn solubility and speciation was carried out with a chemical speciation program (Visual Minteq). The predicted solubilities were in good agreement with the observations, indicating chemical equilibrium. The three methods using pure water were highly correlated with each other and showed the strongest correlation with agronomic effectiveness (r = 0.81–0.90). The methods using extractants with strong pH buffering or high chelating capacity showed no or weak correlation with the agronomic effectiveness. Thus, water‐only based methods give the best indication of the availability of Zn in granular fertilizers, and are best suited for regulation or labeling of available Zn in fertilizer.

Biofortification of Silage Maize with Zinc, Iron and Selenium as Affected by Nitrogen Fertilization

“…Use of water-soluble Zn fertilizer is, therefore, highly desirable for high pH soils. At least 40 to 50% of Zn in each granular fertilizer should be water soluble to achieve a positive agronomic impact on plant growth by using Zn-containing compound fertilizers in high pH soils [ 30 , 46 , 48 ]. Recently, Degryse et al (2020) [ 48 ] emphasized importance and relevance ofwater-soluble Zn in each granular fertilizer and highlighted that water-soluble Zn rather than the total Zn should be considered in the fertilizer labeling regulations.…”

Fate and Plant Uptake of Different Zinc Fertilizer Sources upon Their Application to an Alkaline Calcareous Soil

“…Zinc diffusion was in the order ZnEDTA > ZnSO 4 > Zn mix ≈ ZnO ≈ ZnP. Even though ZnSO 4 is very soluble, it did not diffuse as well as ZnEDTA because of the various adsorption and precipitation reactions occurring in soil, especially in calcareous soils. Zinc-EDTA, by virtue of the chelation of Zn by EDTA, can avoid most soil reactions that lead to Zn fixation and therefore is mobile and diffuse farther.…”

Unraveling the Mechanisms of Zn Efficiency in Crop Plants: From Lab to Field Applications

“…At least 40 to 50% of Zn in each granular fertilizer should be water soluble to achieve a positive agronomic impact on plant growth by using Zn-containing compound fertilizers in high pH soils [30,46,48]. Recently, Degryse et al (2020) [48] emphasized importance and relevance ofwater-soluble Zn in each granular fertilizer and highlighted that water-soluble Zn rather than the total Zn should be considered in the fertilizer labeling regulations.…”