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.

中文翻译：

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评估肥料锌农艺效果的提取方法的比较和建模

肥料中的总锌不能很好地预测粒状肥料中锌的有效性。在这项研究中，我们比较了先前已确定农艺效果的使用锌肥的不同提取方法。通过八种不同的程序，使用五种萃取剂溶液萃取了十六种肥料：水，1 M醋酸铵（pH 7.0），74 mM EDTA（pH 7.0），5 mM DTPA + 0.1 M MES（pH 6.2）和0.12 M bis-tris （pH 6）。Zn溶解度和形态的建模是使用化学形态程序（Visual Minteq）进行的。预测的溶解度与观测值非常吻合，表明化学平衡。三种使用纯水的方法相互之间高度相关，并且与农艺有效性的相关性最强（r= 0.81-0.90）。使用具有强pH缓冲或高螯合能力的萃取剂的方法与农艺效果没有相关性或相关性很弱。因此，基于水的方法可以最好地表明粒状肥料中锌的有效性，并且最适合于调节或标记肥料中有效锌的含量。