Comparison of soil-test extractants for potassium, calcium, magnesium, sulfur, and micronutrients in Idaho soils

Soil fertility and nutrient-management programs across Idaho and the western United States need to consider the effective comparison of various extractants for nutrient analysis. Common extractants for primary (potassium; K), secondary (calcium; Ca, magnesium; Mg, sulfur; S) and micro (zinc; Zn, copper; Cu, manganese; Mn, iron; Fe, aluminum; Al, boron; B, sodium; Na,)-nutrients vary (e.g., ammonium acetate, AA, Olsen). The desire to develop relationships among common tests in the region and those of multinutrient extractants used or proposed in other geographical regions has increased due to the interest in soil health measurements (Mehlich-3; M-3 and Haney, Haney, Hossner, Arnold; H3A). To investigate these multinutrient tests, 46 primarily alkaline soils were sampled from the 0 to 30-cm depth in agricultural fields in Idaho. The majority of nutrients were highly related and relationships were developed. However, for Ca issues were noted for M-3 due to high levels of calcium carbonate in the soil interfering with the test on alkaline soils. Additionally, issues were noted for specific micronutrients when both acidic and alkaline soils were combined in the analysis, but were improved when they were separated. Thus, this research provides specific correlation equations that could be used for comparison among tests as well as provides evidence of the potential suitability of multinutrient extractants in the region