Soils 101

Dr. Bob Lippert

Soil Fertility Specialist

Clemson University

Soil Components

AIR

WATER

Mineral

Organic

Matter

Soil Components

Mineral

Sand = 2.0 to 0.05mm

Silt = 0.05 to 0.002mm

Clay = less than 0.002mm

1 Millimeter between these lines

Six Inch Ruler

50% silt 15% sand 35% clay

Scanning Electron Microscope

Single Cell Animal with “Tail”

???Stink Bug Hatching

Kaolinite

European Union Geochemical facility at Bristol University

Kaolinite

Negative Charge Due To:

• Isomorphic substitution

• Edge-of-clay oxygen ions

• Ionized hydrogen from clay hydroxyl ions

• Ionized hydrogen from organic materials

Isomorphic Substitution

Al+3Mg+2

Plant Nutrients

C HOPKN’S CaFe Mg B Mn Cu Zn Mo Cl

See Hopkin’s Cafe Managed By My Cousin Mo Clay

Major Plant Nutrients

• Hydrogen

• Carbon

• Oxygen

• Nitrogen*

• Phosphorus*

• Potassium*

* = mobile in the plant

Secondary Plant Nutrients

• Calcium

• Magnesium*

• Sulfur

* = mobile in the plant

Micronutrients

• Boron

• Copper

• Manganese

• Zinc

• Iron

• Molybdenum

• Chloride

The terms Major, Secondary and Micronutrients does not imply that some nutrients are more important than others. The term refers to the relative quantity required by the plants.

Sample Corn Crop Nutrient Requirements

• 120 pounds/acre nitrogen (major nutrient)

• 15 pounds/acre magnesium (secondary nutrient)

• 0.5 pounds/acre boron (micronutrient)

The corn yield will be decreased if all of these nutrients are not at optimum soil levels!

Principle of Limiting Factors

Helminthosporium blight

Potassium deficiency

Nitrogen deficiency

Magnesium deficiency

Phosphorus deficiency

Nitrogen Deficiency

Potassium Deficiency

Phosphorus Deficiency

Magnesium Deficiency

Adding fertilizer to the soil without testing is like baking a

cake without:

1. Reading the recipe

2. Measuring the ingredients

100 pound bag of 5-10-15

= 5 pounds of nitrogen

= 10 pounds of phosphorus

= 15 pounds of potassium

Fertilizer Bags

Chemical Forms and Charges of Plant Nutrients

• NH4+, NO3

-

• H2PO4-, HPO4

-2

• K+

• Ca+2

• Mg+2

• SO4-2

• Zn+2

• Mn+2

• Nitrogen• Phosphorus• Potassium• Calcium• Magnesium• Sulfur• Zinc• Manganese

Clay Minerals & Plant Nutrients

K+

Mg+2NH4

+

Ca+2

NO3-

SO4-2

P

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Cation Exchange Capacity (CEC)

One source of the

How Soils Become Acid

Carbonic acid& Pollutants

Nitrogenfertilizers

Aluminum

Iron

Organic Matter

CalciumMagnesium

Potassium

pH

A measure of the concentration of acidic hydrogen ions (H+) in the soil solution

The Buffer pH Measures the Exchangeable and Active Acidity

Determining Lime Requirement

Determining Lime Requirement

NorfolkNorfolk Cecil Cecil

pH = 5.2pH = 5.2 pH = 5.2 pH = 5.2

Buff. pH = 7.6 Buff. pH = 7.4Buff. pH = 7.6 Buff. pH = 7.4

Lime = Lime = 2 t/ac2 t/ac Lime = Lime = 3 t/ac3 t/ac

Ideal

Lime recommendations are based on the type of plant

Blueberries = no lime

Azaleas & Centipede = pH 5.5 to 6.0

Vegetable Garden = pH 6.0 to 6.5

Liming Materials

• Calcitic Lime

• Dolomitic Lime

• Hydrated Lime(Use 75% of the above recommended amount)

• Wood Ashes(Use with caution!)

QuestionsQuestions

http://hubcap.clemson.edu/~blpprt/index.html