Gavlak, R. G.

Michaelson, G. J.

Ping, C. L.

English

ScholarWorks@UA

G.J. MichaelsonResearch AssociatePalmer Research Center, Agricultural and Forestry Experiment StationUniversity of Alaska FairbanksR.G. GavlakAssociate Professor and Extension AgronomistPalmer Research Center, Cooperative Extension ServiceUniversity of Alaska FairbanksC.L. PingAssociate Professor of AgronomyPalmer Research Center, Agricultural and Forestry Experiment StationUniversity of Alaska FairbanksRelating Mehlich 3 extractable Pto Morgan and Bray 1 extractable Pfor Alaska soilsCircular 81 October 1991Agricultural and Forestry Experiment StationSchool of Agriculture and Land Resources ManagementU A FNIVERSITY OF LASKA AIRBANKS2INTRODUCTIONSince 1989 the University of Alaska AFES Soil and Plant Tissue Testing Laboratory has used theMehlich 3 extractant as the routine procedure for testing soil samples submitted through the Coop-erative Extension Service. Before 1989, the Morgans extractant was used for these samples and theBray 1 extractant was used for research soil samples. The change to Mehlich 3 was made based onrecent soil research findings at the University of Alaska AFES.Research on the correlation and calibration of a P soil test for Alaska soils began in 1983. Labo-ratory studies identified the P sorption character of 10 Alaska soils representing both the Interior(Fairbanks, Delta, and Copper River) and Southcentral (Matanuska and Susitna Valleys, Soldotna,Kenai, and Homer) regions. These soils were found to have widely differing P sorption characteris-tics (Ping and Michaelson, 1986). A growth chamber experiment was performed in which the Premoved by seven different P extractants was related to plant growth at various levels of soil P. TheMehlich 3 extractant was found to be most suitable across the wide range of soils tested. The Mor-gans extractant was found to be the least sensitive to changes in soil P, and along with the Bray 1extractant, was found less suitable than Mehlich 3 for use on the soils of volcanic ash origin (SusitnaValley and lower Kenai Peninsula soils) (Michaelson and Ping, 1986).Field trials were carried out from 1984-1987 at five locations (Delta, Copper River, Palmer, Pt.MacKenzie, and Soldotna) to calibrate the Mehlich 3 extractable P soil test for local conditions.Relationships between Mehlich 3 extractable P and yield levels of cereal forages were developed forsix soils (Michaelson and Ping, 1990a). Relationships between Mehlich 3 extractable P and amountof fertilizer added in the field were also developed for each soil (Michaelson and Ping, 1990b). Thefield and laboratory data were used in creating tables for interpreting Mehlich 3 extractable P testswhen making P fertilizer recommendations. These tables vary with soil series across the state(Michaelson and Ping, 1989).Since many years of farm and garden soil test records contain Morgan extractable P values, andyears of research soil tests used Bray 1, the question arises as to how these older soil test P valuesrelate to current Mehlich 3 extractable P values. Equations for relating a soil test P value from oneextractant to that of another were identified for soils at the various locations in the calibration trials(Nenana/Volkmar, Copper River, Knik, Kashwitna, and Soldotna series) and on soils used ingrowth chamber studies (Fairbanks and Kachemak series). These relationships are presented hereto allow conversion of one value to another by calculation. The reader is reminded however, of thelimited suitability of the Morgans and Bray 1 extractants and that the extraction of P by theMehlich␣ 3 extractant is the method generally recommended for use in assessing the P fertility statusof   Alaska soils.3RELATING SOIL TESTSThe linear equations in Table 1 allow the calculation of an approximate value for Mehlich 3extractable P from either Morgan extractable P or Bray 1 extractable P, and vice versa. These rela-tionships vary significantly from soil to soil. The proper equation to be used is the one for the soilclosest in location and with properties most similar to the soil for which the P test is to be con-verted. The major soil series (from published soil survey reports USDA-Soil Conservation Service)to which each equation can be applied are listed in Table 2. Select the proper soil series and find theequation with the soil test extractant value to be converted on the right side of the equation and theone you wish to calculate on the left. Then, multiply your test value (in mg P/kg or ppm P) by thecoefficient and then add (or subtract as the sign indicates) the constant value. This will result in thedesired soil test value in mg P/kg or ppm P.Figure 1 provides graphical representations of the linear equations listed in Table 1. The rela-tionships of either Bray 1 extractable P or Morgan extractable P (on the y-axis) to Mehlich 3 extract-able P (on the x- axis) are presented for eight Alaska soil series. These figures can be used to graphi-cally estimate Mehlich 3 extractable P soil test values from either Bray 1 extractable P or Morganextractable P. Select the graph for the appropriate soil series then find the soil test level for Bray 1 orMorgan extractable P on the y-axis. Draw a horizontal line to the function line of the desired soiltest. At the point where the horizontal line crosses the soil test line, draw a vertical line down to theMehlich 3 extractable P value on the x-axis. This value is the Bray 1 extractable P or Morgan extract-able P soil test value converted to approximately the level the Mehlich 3 P extractant would yield.The graphs and equations should not be used to convert soil test values that are outside therange of points presented in Figure 1. The Fairbanks graph in Figure 1 is extrapolated only forMehlich 3 values less than about 120 mg P/kg.Calculation of soil P values using the linear equations provided in Table 1 will result in approxi-mately the same values as those generated utilizing the graphs in Figure 1. Either method can beused and should provide adequate figures for soil fertility evaluation and calculation of P fertilizerapplication rates.LITERATUREMichaelson G.J., and C.L. Ping. 1986. Extraction of phosphorus from the major agricultural soils ofAlaska. Commun. Soil Sci. and Plant Anal. 17:275-297.Michaelson, G.J., and C.L. Ping. 1989. Interpretation of the phosphorus soil test for Alaska agriculturalsoils. University of Alaska Fairbanks, Agricultural and Forestry Experiment Station. Circular 66.Michaelson, G.J., and C.L. Ping. 1990a. Mehlich 3 extractable P in relation to cereal forage produc-tion on Alaska soils. Appl. Agric. Res. vol 5, no. 4, pp 225-260.4Area (M3) vs (Mo) (M3) vs (B1)Soil series Mehlich 3      vs      Morgans Mehlich 3     vs      Bray 1Soil test in mg P/kg or ppm/PTanana ValleyFairbanks (M3) = 7.27 (Mo) + 11.2 (M3) = 0.98 (B1) + 42.3(Mo) = 0.12 (M3) + 0.1 (B1) = 0.84 (M3) - 16.0Nenana/Volkmar (M3) = 6.67 (Mo) - 14.0 (M3) = 1.05 (B1) + 1.0(Mo) = 0.13 (M3) + 2.6 (B1) = 0.92 (M3) - 0.4Copper River BasinCopper River (M3) = 2.63 (Mo) + 15.3 (M3) = 1.28 (B1) + 1.0(Mo) = 0.27 (M3) + 14.0 (B1) = 0.72 (M3) + 9.6Mat-Su ValleysKnik (M3) = 6.13 (Mo) + 18.7 (M3) = 0.97 (B1) - 3.4(Mo) = 0.15 (M3) - 2.0 (B1) = 1.00 (M3) + 4.7Nancy (M3) = 2.49 (Mo) - 12.0 (M3) = 1.14 (B1) - 0.9(Mo) = 0.34 (M3) + 6.2 (B1) = 0.85 (M3) + 1.1Kashwitna (M3) = 9.58 (Mo) - 32.0 (M3) = 0.86 (B1) + 15.0(Mo) = 0.09 (M3) + 4.3 (B1) = 1.12 (M3) - 15.0Kenai PeninsulaSoldotna (M3) = 5.80 (Mo) - 7.7 (M3) = 1.10 (B1) + 8.7(Mo) = 0.14 (M3) + 2.2 (B1) = 0.86 (M3) - 6.3 Kachemak (M3) = 3.70 (Mo) - 26.0 (M3) = 0.55 (B1) + 8.9(Mo) = 0.24 (M3) + 8.4 (B1) = 1.68 (M3) - 10.0Table 1.   Linear equations for the relationships between soil test P (in mg P/kg or ppm P) extracted by Mehlich␣ 3and Morgans extractants, and Mehlich 3 and Bray 1 extractants for representative Alaska soils.Michaelson, G.J., and C.L. Ping. 1990b. Mehlich 3 extractable P of Alaska soils as affected by Pfertilizer application. Appl. Agric. Res. vol 5, no. 4, pp 261-267.Michaelson, G.J., C.L. Ping, and G.A. Mitchell. 1987.Correlation of Mehlich 3, Bray 1, and ammo-nium acetate extractable P, K, Ca, and Mg for Alaska agricultural soils. Commun. Soil Sci. andPlant Anal. 18:1003-1015.Ping, C.L., and G.J. Michaelson. 1986. Phosphorus sorption by major agricultural soils of Alaska.Commun. Soil Sci. and Plant Anal. 17:299-320.5AreaSoil series Area soil series for which equation may be extrapolated(from Table 1)Tanana ValleyFairbanks Gilmore, Saulich (thawed), Minto, and other upland nonacid loesssoils.Nenana/Volkmar Beales, Chena, Richardson, Steese,Tanana and other soils of the Salcha-Delta area.Copper River BasinCopper River All neutral to alkaline soils of the area.Mat-Su ValleysKnik Bodenburg, Doone, Matanuska, Niklason, and Homestead (mappedalong the Matanuska River and the foothills of Lazy Mtn).Nancy Chulitna, Rabideaux, Talkeetna, Whitsol and other series in theSusitna␣ Valley.Kashwitna Flathorn, Homestead, Kenai, Naptowne, and Shrock series mapped inthe Matanuska Valley and Point MacKenzie/Anchorage areas.Kenai PeninsulaSoldotna Cohoe, Kenai, Naptowne, Tustumena, and other series mapped in theKenai-Kalilof area.Kachemak Beluga, Island, Mutnala, and other land soil series of the Homer-Ninilchik, southeastern Alaska,and southwestern Alaska areas.Table 2. Soil series to which equations given in Table 1 can be extrapolated. The soil series names are taken fromsoil survey reports for each area (published before 1982, USDA-Soil Conservation Service).Figure 1. Relationships between Bray 1 extractable P and Morgan extractable P (y-axis) and Mehlich 3 P (x-axis)by soil series, along with data points used to develop the equation (line) for each.

Circular 81

https://scholarworks.alaska.edu/bitstream/11122/2174/1/C81.pdf

Circular 81

Abstract

Similar works

Full text

Available Versions

ScholarWorks@UA