A New Method for Testing Soil pH Frank Sikora and Paula Howe Division of Regulatory Services IPM Scout Training School March 3, 2010

10 cm 3 soil 10 mL Sikora buffer Lime Recommendations with soil-water pH and Sikora buffer pH soil-water pHSikora buffer pH 10 mL water

Salt NaCl Na + Cl - KCl K+K+ Cl -

Salt (Ca 2+, Mg 2+, K +, NO 3 - ) Salt (K +, Cl -, NO 3 - )

salt

H+H+ K+K+ pHH+H+

Average pH for 11 Southeastern KY counties

D1 D0 D1 D3 D0 D3 Average pH for 11 Southeastern KY counties

Average pH vs Drought Index for 11 Southeastern KY counties

10 cm 3 soil 10 mL Sikora buffer Lime Recommendations with 1 M KCl soil pH and Sikora buffer pH 1 M KCl soil pHSikora buffer pH 10 mL 1 M KCl

Advantages 1. Solves problem with low pH in fall 2. Improves accuracy of lime recommendation

Lime response curve

Buffer pH 1 M KCl soil pH

buffer pH soil- water pH Kentucky LR table based on soil-water pH and Sikora buffer pH

buffer pH 1 M KCl soil pH soil- water pH New LR table based on 1 M KCl soil pH and Sikora II buffer pH

Questions?

extra

pH cmol/kg OH cmol/kg H + 1 M KCl soil pH SMP Typic Fragiudalf silt loam CEC = 7 cmol/kg

Empirical correlations Mechanistic approach Lime required Buffer pH Lime added Soil pH 1 M KCl soil pH Buffer pH Lime response curve

Lime Recommendations with soil pH and soil-buffer pH Soil-water pH Soil-buffer pH

Should the same amount of lime be recommended for the two soils below? Soil-water pH Soil-buffer pH Soil 1Soil 2

Double-buffer method for Lime Recommendations Soil pH Soil-buffer pH Soil-buffer pH These two used to assess pH buffer capacity of soil

pH cmol/kg OH cmol/kg H + SMP SMP with initial pH of 6 soil- water pH

pH cmol/kg OH cmol/kg H + Sikora = SMP 1 M KCl soil pH = 4.3 Soil-buffer pH = 6.4

Target pH = 5.5 Added alkalinity (cmol/kg)

Lime response curve from 1 M KCl soil pH and Sikora buffer pH Titration of soil with KOH in 1 M KCl Titration of soil with KOH in water

1:1 line

Fig. 4 1:1 line c) Correction factor for long-term field neutralization LR = Alkalinity to pH 5.5 x Correction Factor LR using 1 M KCl soil pH and Sikora buffer pH (cmol/kg) Current KY LR M KCl soil pH and Sikora buffer pH LR

Correction factor Current KY LR SMP double buffer LR

Data from Thompson, Kissel, Cabrera, and Sonon (2010)

Lime Recommendations with 1 M KCl soil pH and soil-buffer pH 1 M KCl Soil pH Soil-buffer pH soil-water pH =

1 M KCl soil pH and Sikora buffer pH for Lime Recommendations Advantages 2. Accounts for pH buffer capacity of soil 1. Solves problem with low pH in fall 3. Background electrolyte good for quick and stable pH reading

1 M KCl soil pH = 4.0 Soil-buffer pH = 7.0 Target pH = 5.5

buffer pH soil- water pH Current LR table based on soil-water pH and Sikora buffer pH

Buffer pH response to acid

pH cmol/kg H + SMP Buffer pH

pH cmol/kg OH cmol/kg H + SMP “Lime response curve”

Cut out slides with double buffer explanation

pH cmol/kg OH cmol/kg H + SMP SMP with initial pH of 6 Lime requirement for target pH of 6.5

pH cmol/kg OH cmol/kg H + SMP SMP with initial pH of 6 Lime requirement for target pH of 6.5 ? ? water pH salt pH

Advantages 1) Mechanistic approach for soils of varying buffer capacity 1 M KCl soil pH and Sikora buffer pH for Lime Recommendations 2) Solve problem with lower than expected soil pH during dry falls

1 M KCl soil pH = 4.3 Soil-buffer pH = 6.2 Lime response curve (2 cmol/kg alkalinity = 1 ton/acre CaCO 3 )

Number of samples Average pH for 11 Southeastern KY counties