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1. Both procedures have advantages: Mehlich: higher correlation Bray: visible differences in response Both require more data. 2. Stat. MethodAnal. MethodModelR 2 CL ________________________________________________________________________________________________ - PowerPoint PPT Presentation
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y = 95.522x + 367.35
R2 = 0.9525
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Mehlich P, ug/g
Yie
ld,
kg/h
a
y = 168.16x - 996.34
R2 = 0.8963
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Bray P, ug/g
Yie
ld,
kg/h
a1. Both procedures have advantages:
Mehlich: higher correlation
Bray: visible differences in response
Both require more data
2. Stat. Method Anal. Method Model R2 CL
________________________________________________________________________________________________
Quadratic Bray & Kurtz ___________________________ -970 ____
Linear-Plateau Bray & Kurtz ___________________________ 30 ____
Square Root Bray & Kurtz ___________________________ 1.69 ____
Cate Nelson Bray & Kurtz ___________________________ 23 ____
Quadratic Mehlich III ___________________________ -1.06 ____
Linear-Plateau Mehlich III ___________________________ 34 ____
Cate-Nelson Mehlich III ___________________________ 30 ____
Square Root Mehlich III ___________________________ 5.79 ____
________________________________________________________________________________________________
CL - critical soil test level
3. Need more farmer data
Repeat step 1 until the ideal procedure was identified
Stat. Method Farmer Model R2 FR EFR
________________________________________________________________________________________________
Quadratic 1 ___________________________________ 166 144 ____
Linear Plateau 1 ___________________________________ 100 ____ ____
Square Root 1 ___________________________________ 1244 275 ____
Cate-Nelson 1 ___________________________________ 115 ____ ____
Quadratic 2 ___________________________________ 145 124 ____
Linear Plateau 2 ___________________________________ 50 ____ ____
Square Root 2 ___________________________________ 208 110 ____
Cate-Nelson 2 ___________________________________ 50 ____ ____
Quadratic 3 ___________________________________ 139 106 ____
Linear Plateau 3 ___________________________________ 54 ____ ____
Square Root 3 ___________________________________ 205 74 ____
Cate-Nelson 3 ___________________________________ 75 ____ ____
Quadratic 4 ___________________________________ 138 51 ____
Linear Plateau 4 ___________________________________ 47 ____ ____
Square Root 4 ___________________________________ 170 29 ____
Cate-Nelson 4 ___________________________________ 75 ____ ____
Mitscherlich 1 ___________________________________ 398 146 ____
Mitscherlich 2 ___________________________________ 205 90 ____
Mitscherlich 3 ___________________________________ 202 75 ____
Mitscherlich 4 ___________________________________ 138 40 ____
________________________________________________________________________________________________
FR - recommended fertilization rate
EFR - recommended economic fertilization rate
Mehlich 3 % Sufficiency Fert. Rec.
0-5 10 100
5-15 25 80
15-20 35 60
20-30 65 40
>30 100 0
4. P recommendation Table
Linear-PlateauP2O5
Farmer required Soil Test P1 100 52 50 143 54 184 47 30
35*
y = -0.3319x + 37.577
R2 = 0.63990
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P2O5 required
So
il T
est
PAll sites showed some response to applied P. The need for a site with higher soil test P was evident in this example
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