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Evaluation of soil test phosphorus extractants in Idaho soils

Biswanath, Dari and Rogers, C.W. and Leytem, A.B. and Schroeder, K.L. (2019) Evaluation of soil test phosphorus extractants in Idaho soils. Soil Science Society of America Journal. 9 May 2019.

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Evaluation of soil-phosphorus (P) tests is critical to ensure the accuracy of fertilizer recommendations to optimize crop yield while minimizing negative environmental consequences. Olsen-P is the most commonly used soil-P test for alkaline calcareous soils found in Idaho and the Western United States. The Bray-1 test is commonly used in the Pacific Northwest (PNW) on neutral to acidic soils but underestimates P in alkaline calcareous soils. Mehlich-3 has been evaluated throughout various regions in the United States. Little data evaluating the test exists on soils in the Western United States. Additionally, the comparatively newly developed H3A test, a component of the soil health tool, has not been widely evaluated on alkaline calcareous soils. Soil samples from the 0- to 30-cm depth were collected from agricultural fields throughout Idaho and analyzed using Bray-1, H3A, Mehlich-3, and Olsen P extractants. Results suggested that Olsen P was strongly correlated with Mehlich-3, while Bray-1 and H3A were not correlated with Olsen P. Both the Bray-1 and H3A test underestimated extractable P when compared with the Olsen P test, whereas the Mehlich-3 overestimated. A threshold point in calcium carbonate (i.e., inorganic carbon (IC)) of 6.7 and 5.1 mg kg-1 for the Bray-1 and H3A was obtained, respectively, that indicated inorganic carbon concentrations at or above these levels result in underestimation of extractable soil P. Thus, Mehlich-3 was very strongly correlated to Olsen P and could be evaluated for use in alkaline calcareous soils whereas Bray-1 and H3A have notable issues that would limit their applicability.

Item Type: Article
NWISRL Publication Number: 1650
Subjects: Soil > Calcareous soil
Soil > Chemistry
Depositing User: Users 6 not found.
Date Deposited: 17 May 2019 20:07
Last Modified: 17 May 2019 20:07
Item ID: 1694