Section 6
Chapter 5,062

Correlation of mehlich 3 bray 1 and ammonium acetate extractable phosphorus potassium calcium magnesium for alaska usa agricultural soils

Michaelson, G.J.; Ping, C.L.; Mitchell, G.A.

Communications in Soil Science and Plant Analysis 18(9): 1003-1016


ISSN/ISBN: 0010-3624
Accession: 005061032

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Soil test recommendations currently used in Alaska are based on a limited amount of in-state data along with consideration of data from other states. Recently, Mehlich 3 extractable P has been found to be highly correlated to yield on representative agricultural soils in Alaska. To fully use its multi-element capability, a study was conducted to correlate Mehlich 3 extractable P and cations (K, Ca, and Mg) with the P and cations extracted by the Bray 1 and ammonium acetate methods respectively. When Mehlich 3 extractable K and Mg were regressed with ammonium acetate extractable K and Mg respectively, the relationship was essentially one-to-one and the relationship held across all soils tested. Significant variation was observed among soils in the extraction of Mehlich 3-P and Ca relative to Bray 1-P and ammonium acetate-Ca. Individual soil character appeared to affect the regressions for extractable P and Ca, even though the R2 values were generally high. The regression slopes for Mehlich 3-P versus Bray 1-P ranged from 1.01 and 1.88 with Mehlich 3 extracting an average of 66% more P than Bray 1 in the volcanic ash soils, and 12% more in the loess soils. The regression slopes for Mehlich 3-Ca versus ammonium acetate-Ca ranged from 0.95 to 1.33, and the former extracted an average of 17% more Ca than the latter. It is suggested that the regression data of P and Ca can be extrapolated to other soils based on soil classification; to extend the soil test data over a geographic base.

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