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Improved Corrective Fertilizer Recommendations Based on a Two‐Step Alternative Usage of Soil Tests: II. Recovery of Soil‐Equilibrated Potassium
Author(s) -
McLean E. O.,
Adams J. L.,
Hartwig R. C.
Publication year - 1982
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1982.03615995004600060016x
Subject(s) - fertilizer , soil water , potassium , soil test , chemistry , mathematics , soil science , environmental science , mineralogy , organic chemistry
The objective of these studies was to improve corrective fertilizer K recommendations using soil quicktest methodology which measures K‐fixation tendencies for individual soils. Actual amounts of fertilizer K required to reach a computed sufficiency level of NH 4 OAc‐exchangeable K were measured from the added K vs. exchangeable‐K relationship in 15 soils with a wide range in K‐fixation tendency. Using quicktest procedures, the new Mehlich extractant removed from the various K‐equilibrated soils the same amounts of K as did NH 4 OAc solution, which suggests the possibility that both K and P may be simultaneously equilibrated and extracted with one extractant. Regressions were computed between the actual and variously computed amounts of K to reach sufficiency level based on constant‐fraction recovery, quicktest‐measured recovery (one‐step), and curvilinear regression‐adjusted recovery (two‐step). The results indicate that the proposed quicktest methodology (2‐h K equilibration) combined with a second calibration step based on longer‐time K equilibration of representative soils makes possible a greatly improved recommendation for fertilizer K.