Median Absolute Deviation MAD Relative Median Absolute Deviation

Median Absolute Deviation MAD % Relative Median Absolute Deviation %RMAD = MAD / median x 100

Intralaboratory precision Within Interlaboratory precision Between

q ICP vs colorimetry to analyze P q Calculated CEC q Salt p. H q Nitrate analysis q Combustion C and Ca. CO 3 q Scooping versus weighing q Hot-water and Mehlich-3 B q Micropipette method for soil texture

ICP vs colorimetry to analyze P

ICP vs colorimetric P ICP labs = 39 colorimetric labs = 21

%RMAD (MAD/MED x 100) ICP vs colorimetric P 45 40 35 30 colorimetric ICP 30 40 50 P conc, mg/kg 60 25 20 15 10 5 0 0 10 20 70

ICP vs colorimetric P

Calculated CEC

Calculated CEC ? 1 M NH 4 OAc CEC at p. H 7 = sum of bases + acidity

Ca 35 Mg 6 0. 4 5 15 5 0. 3 4 M 3 K - Amm. Acc K M 3 Mg - Amm. Acc Mg M 3 Ca - Amm. Acc Ca 25 3 2 1 4 5 6 7 1: 1 soil p. H 8 9 -1 0. 2 0. 1 0. 0 -0. 1 0 -5 K 4 5 6 7 8 1: 1 soil p. H 9 -0. 2 4 5 6 7 8 1: 1 soil p. H 9

calc CEC - Amm Acetate CEC 25 20 15 10 5 0 -5 -10 4 6 1: 1 soil p. H 8

Northeastern Region Methods Manual Calc CEC, meq/100 g 40 30 lin 1 1: R 2 = 0. 7453 e 20 10 Exchangeable acidity = 12. 6 – (1. 64 x soil p. H) – (0. 48 SMP buffer p. H) 0 0 10 20 30 NAPT NH 4 OAc CEC median +- MAD, meq/100 g 40

Northcentral Region Methods Manual Calc CEC, meq/100 g 40 R 2 30 e in 1 l = 0. 8506 1: 20 10 Exchangeable acidity = 12 x (7 – SMP buffer p. H) 0 0 10 20 30 40 NAPT NH 4 OAc CEC median +- MAD, meq/100 g

Current calculation at Univ. Kentucky 40 Calc CEC, meq/100 g R 2 = 0. 8715 30 in 1 l e 1: 20 Acidity = 8 x (7. 5 – SMP buffer p. H) 10 0 0 10 20 30 NAPT NH 4 OAc CEC median +- MAD, meq/100 g 40

Using 1 M KCl soil p. H & Sikora-2 soil-buffer p. H Calc CEC, meq/100 g 40 30 e R 2 = 0. 8755 in 1 l 1: 20 10 0 0 10 20 30 NAPT NH 4 OAc CEC median +- MAD, meq/100 g 40

Salt p. H

9 0. 01 M Ca. Cl 2 soil p. H 8 e in 1 l 7 1: 6 5 4 3 4 5 6 7 soil water p. H 8 9

soil water p. H - 0. 01 M Ca. Cl 2 p. H 1. 2 1. 0 0. 8 0. 6 0. 4 0. 2 0. 0 0. 5 1. 0 1. 5 2. 0 1: 1 EC, d. S/m 2. 5 3. 0

Nitrate analysis

80 Ion selective electrode nitrate reduction 60 critical value %RMAD (MAD/MED x 100) 70 50 40 30 20 10 0 0 20 40 NO 3 -N conc. , mg/kg 60 80

Combustion C and Ca. CO 3

3. 5 % C from Ca. CO 3 3. 0 2. 5 2. 0 1. 5 1. 0 0. 5 0. 0 4 5 6 7 1: 1 soil p. H 8 9 10

% C from Ca. CO 3 10 1 0. 01 0. 001 4 5 6 7 1: 1 soil p. H 8 9 10

Scooping versus weighing

2 soil density, g/cm 3 1. 8 R 2 = 0. 4661 1. 6 1. 4 M 1 assumes 1. 25 g / cm 3 1. 2 M 3 assumes 1. 18 g / cm 3 1 0. 8 0. 6 0 20 40 % sand 60 80 100

g/ g / cm 3 % OM % sand

2 soil density, g/cm 3 1. 8 + 40% 1. 6 1. 4 1. 2 M 3 assumes 1. 18 g / cm 3 1 0. 8 - 40% 0. 6 0 20 40 % sand 60 80 100

55 assume 3 mg/L in M 3 extract 50 Mehlich 3 P, mg/kg 45 40 35 1. 7 cm 3 scoop & 1. 18 g / cm 3 30 25 20 15 10 0 20 40 % sand 60 80 100

Hot-water and Mehlich-3 B

1. 6 Hot water B, mg/kg 1. 4 1. 2 1 0. 8 0. 6 0. 4 0. 2 0 0 0. 2 0. 4 0. 6 0. 8 1 Mehlich B, mg/kg 1. 2 1. 4 1. 6

1. 6 Limit of quantification = 0. 05 mg/L Hot water B, mg/kg 1. 4 10 g 20 m. L 1. 2 1 0. 8 0. 6 0. 4 0. 2 0 0 0. 2 0. 4 0. 6 0. 8 1 Mehlich B, mg/kg 2 g 20 m. L 1. 2 1. 4 1. 6

%RMAD (MAD/MED x 100) 90 80 70 Mehlich-3 Hot water 60 50 40 30 20 10 0 0 0. 2 0. 4 0. 6 0. 8 B, mg/kg 1 1. 2 1. 4 1. 6

Micropipette method for soil texture

Clay analysis % Clay, micropipette method 60 50 R 2 = 0. 786 40 e in l 1 1: 30 20 10 0 0 10 20 30 40 % Clay, NAPT median 50 60