FERTILIZERS

Fertilizer Defined
Fertilizer
– material applied to soil or plants to supply essential elements
Four categories:
Mineral Inorganic
Organic Synthetic Organic

Fertilizer Forms
Four main groups:
1)
2)
3)
4)
Pressurized liquids
Fluids
Dry fertilizers
Slow-release fertilizers

Pressurized Liquids
Anhydrous Ammonia
Ammonia is gas at normal temperature and pressure, but . . .
- changes to liquid when cooled to -28ºF
- stored in high-pressure or refrigerated tanks
- transferred to smaller tanks for field apply
- liquid is injected into soil

Fluid Fertilizers
Nonpressure solutions
Suspensions
Popular due to flexible application:
- sprayed
- injected
- mixed in irrigation water

Dry Fertilizers
Dissolve in soil water to release nutrients
Three types:
1) Pulverized fertilizers
2)
3)
Granules
Prills

Slow-Release Fertilizers
Dry form; dissolve slowly over weeks/months
Widely used in horticulture
Release nutrients as crops use them
Little loss to leaching
Environmentally friendly

Fertilizer Materials
Compounds called Nutrient Carriers
Primary Macros:
- Nitrogen Carriers
- Phosphorus Carriers
- Potassium Carriers

Nitrogen Carriers
-
Haber Process
Uses nitrogen (N
2
) from air
Natural gas (H
2
) is Hydrogen source
Heat + Pressure + iron catalyst
Anhydrous Ammonia (82 percent N) results
Reacts with water in soil to release ammonium ions

Nitrogen Carriers
-
-
-
-
-
-
-
Anhydrous may be used directly, or changed to other
N forms:
Aqua ammonia (20 percent N)
Ammonium nitrate (33 percent N)
Ammonium sulfate (21 percent N)
Sodium nitrate (16 percent N)
Urea (46 percent N)
Urea-ammonium nitrate (UAN, 28/32 percent N)
Urea-formaldehyde, IBDU, and SCU

Phosphorus Carriers
-
-
-
-
-
-
Mined rock phosphate; Mineral is Apatite
Usually treated with acid to break down into simpler compounds (see fig. 14-8)
Rock phosphate
Superphosphate
Triple superphosphate
Phosphoric acid
Ammonium phosphates
Bone meal and manure (organic sources)

Potassium Carriers
Potash Mines – mixtures of potassium, sodium, and magnesium salts
Processed to purify the potassium (fig. 14-10)
Potassium chloride
Potassium sulfate
Potassium nitrate
Sulfate of potash-magnesia