Soil Fertility

• Measure of the nutrients in a soil available for plant life;

• Macronutrients: N-P-K– Nitrogen, Phosphorus, Potassium

• Secondary:– Calcium, Magnesium, Sulfur

• Micronutrients: – BORON (B)  -IRON (Fe) – CHLORINE (Cl)  -MANGANESE (Mn)– COPPER (Cu)    -MOLYBDENUM (Mo) – ZINC (Zn)

Fertilizers: N-P-K

• N is for % Nitrogen• P is for % Phosphorus• K is for % Potassium• If a fertilizer is 10 – 10 – 10. It is a

Balanced fertilizer for general purpose use. It has 10% each of the macronutrients and 70% filler to make application easier

• Lawn fertilizer would have a balance like 16 - 4 - 4.

Soil testing

• Test kit for NPK

• Send off samples to extension service for micronutrients

• New testing for biological activity

• Applying fertilizer with out a soil test is a potential waste of money and harmful to the environment

Nitrogen

• Start-up fertilizer

• Green growth

• Need most for grasses

• Don’t add to fruiting plants except at initial planting– Get green growth & no flowers & fruit

• Nitrogen deficiency – yellow color

Soil Amendments Nitrogen

• Nitrate of Soda: Inorganic, Soluble & quickly available. Lowers acidity. 16% N

• Ammonium nitrate: Inorganic, Not as soluble. 33%N

• Ammonium sulfate: Inorganic, Lower solublilty. Makes soil acidic. 21% N

• Urea formaldehyde: Organic, available more slowly, 38%N

Leaching

• The more soluble a fertilizer is– The quicker it is available to plants– The faster it washes (leaches out of the soil)

• Insoluble fertilizers – Also called slow release fertilizer – releases

throughout the growing season.– Some fertilizers are coated to slow their

release

Phosphorus amendments

• Superphosphate: 20% P• Treble superphosphate: 46% P• Rock phosphate: 25 – 35% P• Ammonium phosphate: 48% P

• Held tightly by soil so does not leach• Excess application does the most damage

to lakes & streams

Potassium Amendments

• Muriate of potash: 60% K

• Sulfate of potash: 49% K

• Nitrate of potash: 44% K

pH

• Lime is added to increase the pH.• Sulfur or iron sulfate or Mg Sulfate is added to

decrease the pH for acid loving plants.• Acid favoring plants;

– Hollies, Camellias, Azaleas, Rhododendrons, – Hydrangeas – blooms change color based on pH.– Vegetables: egg plant, potatoes, & watermelon

• Lime also supplements calcium (minor nutrient). Piedmont Virginia soils are frequently calcium deficient

Organic Amendments

• Compost – adds tilth, ?-?-?, relatively low• Cottonseed meal: 7-3-2• Fish emulsion: 5-1-1• Bonemeal: 4-12-0• Bloodmeal: 11-0-0• Manure: 1-1-1• Sewage sludge: 2-1-1*

– *May not be eligible for organic certification

Soil texture

• Mineral material - different sizes– Sand– Silt– Clay

Types of Soils

• Particle Size– Sand– Silt– Clay

• Soil Classification– Sandy Soil– Clayey Soil– Loamy Soil

Soil Texture Test

• Sand – largest & heaviest particles– Sinks to bottom– Forms bottom layer

• Silt – lighter than sand – Sinks slower– Forms 2nd layer

• Clay – Small particles – hold e- charge– Stay in suspension

Soil Texture Test

• Need 2 values– Clay– Silt

• The 3rd is the remainder from 100

Bottom

Original Fill Line

60%

30%

Sand + Silt + Clay = 100%

Texture = Sandy Loam

60 % Sand30 % Silt10 % Clay

Sandy soils:

• Low in organic matter content and native fertility, • Low in ability to retain moisture and nutrients, • Low in cation exchange and buffer capacities, • Rapidly permeable • Sandy soils usually have high bulk densities• Resist compaction

Loamy Soils

• More fertile:– more organic matter, – have higher cation exchange and buffer

capacities,

• Are better able to retain moisture and nutrients

• Moderate movement of air and water.

• Moderate resistance to compaction

Clayey Soils

• Drain poorly

• Hold nutrients tightly

• Very high cation exchange capacity

• Compact easily & dry very hard

• Very plastic - can shrink & swell

What is the best soil?

• "Best for what?"

• Growing Crops?

• Stable Buildings?

• Building Ponds?

• Good Drainage?