Soil Acidity

Effect of pH and Aluminum on Corn Yield in PA

• Active Acidity

Soil Acidity

• Potential Acidity

Soil Acidity

Mg H + Ca ++ H + Mg ++ Ca ++ Al +++ Ca ++ NH 4 + Ca ++ Al +++ H + K + ++ Mg ++ Al +++ Ca ++ H Ca Ca ++ + ++ K + Quantity: Potential Acidity Buffering H + H + H + H + Intensity: Active Acidity pH

Soil Acidity

• Soil Acidity Buffering – Soils tend to buffer pH • High clay and/or organic matter greater buffering • Low clay and/or organic matter lower buffering

Clay Loam CEC = 25 meq/100g Silt Loam CEC = 15 meq/100g Sandy Loam CEC = 10 meq/100g Sand CEC = 5 meq/100g

pH Textbook Fig. 3.5

Soil Acidity and Liming

Soil Acidity

• Determining exchangeable acidity – 1 eq. Base for each 1 eq. of Acidity – Titration • Add increasing amount of base measure pH change Added Base

Soil Acidity

• Determining exchangeable acidity – Buffer pH • Add a pH buffer solution and measure pH change • Known relationship between pH change and change in acidity • Common pH buffers – SMP (used in PA) » Triethanolamine » Paranitrophenol » Potassium chromate » pH 7.5

– Adams-Evans – Mehlich – Woodruff

NOTES

Soil Acidity

• Determining exchangeable acidity – Buffer pH • Add a pH buffer solution and measure pH change • Known relationship between pH change and change in acidity • Common pH buffers – SMP (used in PA) » Triethanolamine » Paranitrophenol » Potassium chromate » pH 7.5

– Adams-Evans – Mehlich - Many states including PA going to this – Woodruff

Soil pH & Buffer pH

H + H + H + H + H + H + H +

Soil pH

H + H + H + H + H + H + Water SMP Buffer H + H + H + H + H + H + H + H + H + H + H + H + H + H + H + H + H + H + H + H +

Buffer pH

SMP Buffer Curve

8 7.5

7 6.5

6 5.5

5 0 0.2

0.4

0.6

Acidity (meq H+) 0.8

1

7.0

6.8

6.6

6.4

6.2

6.0

5.8

5.6

5.4

SMP Buffer Relationship

Buffer pH Exch. Acidity (meq/100g) 2 3 4 7 9 11 14 16 19 Lime Rec.

For pH 6.5

(lb/A) 0 2000 3000 5000 8000 10000 12000 14000 16000 aasl.psu.edu

Soil Acidity and Liming

• Determining Lime requirement – Exchangeable Acidity • 1 meq. Base/100g for each 1 meq. of Acidity/100g • How many pounds of lime do we need per acre?

Soil Acidity and Liming

• Determining Lime requirement – Desired pH • Acid sensitive crops pH 7.0

• Most crops and soils pH 6.5 • Highly weathered soils pH 5.5

• Acid loving crops 5.5 - 6.0

Soil Acidity and Liming

• Determining Lime requirement – Based on target pH and Exchangeable acidity

Formulas used by PSU AASL

• For pH 7.0

84500 – (12180 x SMP Buffer pH) = CaCO 3 /A • For pH 6.5

71240 – (10280 x SMP Buffer pH) = CaCO 3 /A • For pH 6.0

57840 – (8340 x SMP Buffer pH) = CaCO 3 /A

Soil Acidity and Liming

• Determining Lime requirement – Rules of thumb • For pH 7.0

Exch. Acidity (meq/100g) X 1000 = CaCO 3 /A • For pH 6.5

Exch. Acidity (meq/100g) X 840 = CaCO 3 /A • For pH 6.0

Exch. Acidity (meq/100g) X 750 = CaCO 3 /A

Soil Acidity and Liming

• Liming Materials – Material that will neutralize soil acidity • Calcium Oxide (CaO) – Lime, burnt lime, quick lime • Calcium Hydroxide (Ca(OH) 2 ) – Hydrated lime, slaked lime • Calcium Carbonate (CaCO 3 ) – Calcitic limestone • Calcium/Magnesium Carbonate (Ca,MgCO 3 ) – Dolomitic limestone

Soil Acidity and Liming

• For each equivalent of acidity we need to apply 1 equivalent of liming material • Chemical neutralizing ability of liming materials – Equivalents of OH produced by the reaction of the liming material.

• Ca(OH) 2 → Ca 2+ + 2 OH • CaCO 3 + H 2 O → Ca 2+ + 2 OH + CO 2 • CaO + H 2 O → Ca 2+ + 2 OH • CaSiO 3 + H 2 O → Ca 2+ + HSiO 3 • CaSO 4 → Ca 2+ + SO 4 2 + OH -

Soil Acidity and Liming

• Soil Liming Reaction CaCO 3 → Ca 2+ + CO 3 2 Acid Soil Al 3+ Al 3+ H + Al 3+ + Ca 2+ + CO 3 2 Ca 2+ Ca 2+ Ca 2+ Ca 2+ Ca 2+ + H + + Al 3+ + CO 3 2 + 2H 2 O Exchange Neutral Soil H 2 O + Al(OH) 3 H Neutralization + + Al 3+ + CO 2 + 2OH + H 2 O

Soil Acidity and Liming

• Liming material quality • Calcium Carbonate Equivalent (CCE) – Neutralizing value of any liming material compared to pure calcium carbonate

Soil Acidity and Liming

• Calcium Carbonate Equivalent (CCE) – 1 Eq. of CaCO 3 = 1 Eq. of any liming material

Soil Acidity and Liming

• Calcium Carbonate Equivalent – Example: MgCO 3 MgCO 3 CaCO 3 = 84 g/mole or 42 g/ eq.

= 100 g/mole or 50 g/ eq.

Soil Acidity and Liming

• Calcium Carbonate Equivalent (CCE) Material CaCO 3 MgCO 3 (Ca,Mg)CO 3 CaO Ca(OH) 2 CaSiO 3 Common Limestones % CCE 100 119 109 179 136 86 80 - 100

Soil Acidity and Liming

• Soil test recommendations are made as lb CCE/A • Adjust if CCE is different from 100% – Example: • Recommendation = 2000 lb CCE/A • Hydrated Lime Ca(OH) 2 CCE = 136% • Required amount of liming material = 100 x Rec. CCE/A % CCE of Material

Soil Acidity and Liming

• Real World – Not usually dealing with pure materials, so we can't always calculate the CCE – Measure CCE in lab – Required in most states • Titration with standard acid – CCE is provide on the label for all liming materials sold in PA – Be careful calculating CCE on unknown materials

Estimating Neutralizing Value of Liming Materials - Be very careful • Ca x 2.5 = CaCO 3 • Mg x 3.5 = MgCO 3 • MgCO 3 x 1.19 = CaCO 3 • MgO x 2.5 = CaCO 3 • CaO x 1.79 = CaCO 3

You have to know the form of the Ca or Mg to use these conversions!

Unknown material analysis given as 23% Ca

Estimating Neutralizing Value of Liming Materials - Be very careful • If you don’t know what the material is made of then you need to measure the CCE directly!

• Cost ~ $10-15

Soil Acidity and Liming

• Calcium Oxide Equivalent (COE) – Neutralizing value of any liming material compared to pure calcium Oxide – 1 Eq. of CaO = 1 Eq. of any liming material – 1 Eq. wt. of CaO = 1 Eq. wt. of any liming material COE = eq. wt. CaO/ eq. wt. Liming material COE = 28/ eq. wt. Liming material

Soil Acidity and Liming

• Soil test recommendations may be made as lb COE/A • Adjust if COE is different from 100% • Required amount of liming material = 100 x Rec. COE/A % COE of Material

Soil Acidity and Liming

• Physical fineness of liming materials – Fineness determines speed of reaction – The finer limestone is ground the faster it will react – Fineness given as % passing specific screen mesh sizes

Soil Acidity and Liming

Effect of aglime fineness on speed of reaction 7

100 Mesh 60-80 Mesh 40-60 Mesh

Equal neutralizing value applied 6

20-40 Mesh

5

8-20 Mesh No Lime

4 0 12 24 36 Reaction Time (Months)

Soil Acidity and Liming

• Physical fineness of liming materials – Practical Limits to fineness – Larger than 20 mesh – not effective – Smaller than 100 mesh – little added benefit

6 7

Soil Acidity and Liming

Effect of limestone fineness on soil pH change 100 M 60-80 M 40-50 M 30-40 M 20-30 M 8-20 M 5 0 1 3 5 10 Tons per acre

Soil Acidity and Liming

Particle Size Distribution from Grinding 99.9

99 95 80 50 20 5 0 200 100 60 40 20 8 Sieve Size (Mesh)

Soil Acidity and Liming

• Aglime Fineness – Pulverized Limestone • Normal ground Limestone – Granular Limestone • Coarser ground limestone • Easy spreading for homeowners • Slower to react

Aglime Fineness

Fineness definitions for PA Fine Sized Materials Medium Sized Materials 95% - 20 mesh sieve 90% - 20 mesh sieve 60% - 60 mesh sieve 50% - 100 mesh sieve 50% - 60 mesh sieve 30% - 100 mesh sieve Coarse sized materials

-

all liming materials failing to meet the above fineness criteria

Aglime Quality

• Acid-Base Chemistry and Fineness • CaCO 3 + H 2 O  Ca 2+ + H 2 CO 3 + 2OH 2OH + 2H +  2H 2 O For a given amount of acidity an equivalent amount of base (liming material) will be required regardless if it is ground very fine.

Aglime Quality

•Acid-Base Chemistry in soils 1 meq/100g acidity in the soil will require 1 meq/100g of CaCO 3 to neutralize it.

1 meq CaCO 3 /100g soil = 1000 lb CaCO 3 /A

Soil Acidity and Liming

• Aglime Fineness – No matter how fine you grind limestone you cannot increase the chemical neutralizing ability – Finer the better, because it will react faster, but there are practical limitations – Distribution in “Fine Size” Limestone – usually adequate for practical liming for field crops – Little difference between calcite and dolomite

Soil Acidity and Liming

3 2 1 Effect of type of limestone and rate required for equal crop response 5 Dolomitic 2-4 yr 4 Calcitic 0 20 40 60 80 100 % Passing 60 Mesh

Soil Acidity and Liming

• Pellet Lime – Finely ground limestone – Glued together into water soluble pellets – Advantage: Handling, spreading, speed of reaction – Disadvantage: Cost 100-200 mesh

Soil Acidity and Liming

• Fluid Lime – Finely ground limestone – Suspended in water with clay – Approx. 1000 lb CCE/ton material – Advantage: Spreading, speed of reaction – Disadvantage: Cost

Less than recommended very fine limestone applied compared to normal liming program 7 6 5 4 3 0 3 6 9 Reaction Time (years)

Less than recommended very fine limestone applied annually but similar rate over time.

7 6 5 4 0 3 6 9 Reaction Time (years)

Soil Acidity and Liming

Effect of Pellet Lime on Soil pH

0 -0.2

-0.4

-0.6

0.8

0.6

0.4

0.2

Start 1994 1995 1996 1997 Pellet Lime @ 500lb/A/yr Pulverized Lime @ 8000 lb/A

Soil Acidity and Liming

• Calcium and Magesium – Normal liming practices will also supply required calcium and magnesium • At normal rates usually adequate Ca will be supplied for most crops • Magnesium will depend on the type of limestone used – If Mg is required use a Mg containing limestone (dolomitic) – Mg recommendations » pounds Mg/A » % Mg in recommended limestone

Calcium and Magnesium

• Management Recommendations – Maintain optimum pH – Maintain at least optimum levels of Mg (60 ppm) and K (100 ppm) – Don’t worry about ratios until they are way out of balance • eg. Mg:Ca >1, K:Mg>1 • Rare

By-product Liming Materials

• Quality

–Liming value –Undesirable components

Example: Liming Value

Material sold in western PA for $2/ton CCE = 5.38% For 1 ton of neutralizing value: 2000 X 100 ÷ 5.38 = 37,174 lbs. or 18.6 tons ($37.20) Fineness: Through 20 Mesh = 98.8% (90%) Through 60 Mesh = 78.2 % (60%) Through 100 Mesh = 63.2% (50%)

Gypsum

• CaSO 4 • Excellent source of Ca and S – 33% Ca & 27% S • No neutralizing value • Not a liming material

Limestone vs Gypsum

• Limestone changes pH  Gypsum doesn’t • Both are good sources of Ca – Lime to recommended pH . . . no need for additional Ca for the soil or for agronomic crops in PA – High pH but low calcium soils (Sodic Soils) use gypsum as a source of Ca for the soil and the crop (Western US) • Improves physical properties  Relieves chemical compaction – Low pH, acid loving crops or highly weathered soils, use gypsum as a source of Ca for the soil and the crop (Tropics) • Minimal lime to reduce Al toxicity

Byproduct Materials

Undesirable components • Should be registered (PDA) • Must be approved for land application by DEP – May limit lifetime application • Problem with unregistered materials and materials from out of state – May be little or no checking of quality • Determine the source – Dust, screenings – Stainless steel slag • Ask what contaminants might be present • If in doubt . . . get it analyzed OR don’t use it

Example: Undesirable components Metals in Aglime

Material Aglime Aglime Aglime Aglime Aglime Ind. Byprod. Ind. Byprod. Ind. Byprod. Ind. Byprod. Ind. Byprod. Ind. Byprod. Cu .02 .02 .03 .01 .01 .04 .04 .03 .03 .02 68 Zn .03 .02 .02 .05 .05 .05 .08 .00 .27 5.62 160 Pb .05 .05 .04 .07 .07 .10 .20 .07 .09 .08 19 Cr .02 .02 .02 .02 .02 .03 .04 .03 .04 .02 2037 Ni .04 .04 .04 .04 .04 .07 .05 .05 .08 .06 435 Cd .00 .00 .00 .00 .00 .00 .00 .00 .00 .01 5

Other Materials

• Biosolids and Water Treatment Sludges – Often have significant neutralizing value – Must be clean – Must be registered if sold as liming materials

Other Materials

Organic Calcium Compounds • Promesol 30, Liquid Lime – Trihydroxy glutaric acid 25% Ca – 1 gallon = 500-750 lb CCE?

• Liqui-Cal – 8% Ca – 1 gallon = 500 lb CaCO 3 ?

• Liqui-Til – Trihydroxy glutaric acid – Neutralizes pH in alkaline soil?

• Liquid Calcium – 1 gallon = Ca in 500 lb CaCO 3 ?

– Suggest it is a lime substitute • KK Organic Soil Builder – Neutralizes both acidic and alkaline soils?

• Golden Cal – Glucoheptomic acid – 1 gallon = 500 lb CCE?

• pH Plus – 1 gallon = 500-750 lb CCE?

Other Materials

• Remember: 1 Eq. of base is required to neutralize 1 Eq. of acid • Watch out for materials that contain Ca with unwritten or suggestive claims for liming value

Soil Acidity and Liming

• Limestone Application – Apply limestone far enough ahead of time to be effective – Spread limestone uniformly • Spinner spreaders • Boom spreaders • Damp lime • Dust – Spit high rates of limestone (>4 ton/A) – Time of year is not too critical • Consider soil quality issues – compaction – Mix limestone as much as practical • Adjust for depth of mixing - 6 2/3 in. standard depth • No till – Correct pH before going to no-till

Soil Acidity and Liming

Soil pH vs No-Till With 6000 lbs/A of Lime Applied Every 3rd Year

Time (years)