Transforming Soil Test Data: Comparing Mehlich-3, Bray P, and Ammonium Acetate Indexes
In a recent study, soil samples from Ohio and Indiana were analysed for Mehlich-3, Bray-P, and ammonium acetate extractable nutrients for phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). The analysis, which included a greater diversity of soils across two states, has provided robust findings that will shape the updated Tri-State Fertilizer Recommendations.
The study reveals that Mehlich-3 is set to become the new standard for fertilizer recommendations, as it is a reliable extractant and will be the basis for the updated recommendations. This extractant has been found to be an appropriate and reliable soil test extractant for non-calcareous soils.
One of the key findings of the study is the conversion factors for the extractants. For phosphorus (P), to convert Mehlich-3 P to Bray P within the agronomic range (<50 ppm), you should divide Mehlich-3 P by 1.35. Conversely, to convert Bray P to Mehlich-3 P within the same range, you should multiply Bray P by 1.35.
Similarly, for potassium (K), to convert from AA-K to Mehlich-3 K, you should multiply AA-K by 1.14, and to convert from Mehlich-3 K to AA-K, you should divide Mehlich-3 K by 1.14. In the agronomic range of <200 ppm, Mehlich-3 K extracted 14 percent more K than AA-K.
For calcium (Ca) and magnesium (Mg), the conversion values are reported in Table 2, but it's worth noting that Mehlich-3 Ca and Mg extracted more of their respective elements than AA-Ca and AA-Mg, with Mehlich-3 Ca extracting 15 percent more Ca and Mehlich-3 Mg extracting 24 percent more Mg. To convert from Ammonium Acetate-Ca to Mehlich-3 Ca, multiply by 1.15, and to convert from Ammonium Acetate-Mg to Mehlich-3 Mg, multiply by 1.24.
The relationships between Mehlich-3, Bray P, and Ammonium Acetate soil test extractants in the Tri-State Region have been discussed in the article. However, the search results do not provide information about the names of the authors who presented the re-evaluation of fertilizer recommendations for the Dreistaat area.
The findings of the study suggest that the updated Tri-State Fertilizer Recommendations will be more accurate and reliable, as the Mehlich-3 extractant provides a more comprehensive analysis of the soil's nutrient content. This shift in standards is expected to lead to improved crop yields and overall agricultural productivity in the region.
