Lawn and Garden Learning Center

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Fertilization

The earth’s soil is a rich storehouse of nutrients essential to the growth, beauty and good health of plants. Science tells us that plants must have 16 basic nutrients available to them through the soil and air. But different soils contain varying amounts of the nutrients required to support growth and development. When a soil does not contain enough of a particular nutrient, a fertilizer must be used. Fertilizers are supplemental feedings of nutrients not found in the soil in a sufficient quantity to satisfactorily promote plant growth and good health.

Of all the essential nutrients, Nitrogen (N), Phosphorus (P), and Potassium (K) are required in relatively large quantities and usually need to be supplemented.

Benefits of Fertilizing

1) To promote new growth and hardiness

2) To relieve stress, effects of aging and wear.

3) To counteract damage due to insects or disease.

4) To eliminate competition with weeds for available nutrients.

5) To help replace nutrients lost to leaching, volatilization to the air, and removal of clippings and harvest of fruits and vegetables.

Basics of Fertilizer

The three large numbers printed on each fertilizer bag (sometimes called “NPK” number) indicate analysis or grade.

These numbers refer to the guaranteed percentages of:

Nitrogen (N)
Phosphorus (expressed as P2O5
Potash (expressed as K20)

and are always printed on the bag in that order.
Ratio refers to the amounts of nitrogen, phosphorus and potash on any given product.

For Example: A 16-4-8 analysis indicates a 4-1-2 ratio.

A 12-6-6 analysis indicates a 2-1-1 ratio.
This ratio can also be expressed as a percentage: 16-4-8 indicates 16% nitrogen, 4% phosphorus and 8% potash... or 16 pounds of nitrogen, 4 pounds of phosphorus and 8 pounds of potash per 100 pounds of fertilizer.

The fertilizer analysis printed on the product label indicates the quantity of the nutrient content, not the quality, or type of nutrients used in the product. For example, some fertilizers may be organic while others are inorganic, but both are designed to achieve similar results.

Basic Types of Fertilizer

There are three basic types of nitrogen fertilizer. Organic, Inorganic and Synthetic Organic. Each offers particular benefits depending on use.

Natural Organics are composed of hydrocarbon compounds, which are derived from decaying matter. Examples include: animal manure, bone meal, dried blood, compost, peat moss and treated tankage. Organic Fertilizers are essentially non-burning and long lasting since they break down usable nitrogen over a period of 8-10 weeks.

Inorganics are composed of mineral compounds which are derived from non-living matter such as ammonium nitrate, ammonium phosphate and calcium nitrate. This is usually lower cost fertilizer...specifically used for fast greening, and not for long term feeding. Burning can occur if not used carefully.

Synthetic Organics - These combine benefits of quick greening with long lasting non-burning properties of the natural organic group. They are derived from urea compounds and need a combination of natural elements (temperature, sun, rain and microorganisms in the soil) to become usable plant nutrients.

Sulfur Coated Urea (SCU)
Urea Formaldehyde (UF)
Urea
Polymer Coated SCU (PCSCU)
W.I.N. - Water Insoluble Nitrogen. This term is generally expressed as a percentage of the fertilizer which is composed of Slow Released Nitrogen to extend the feeding cycle.
Nitrogen

• To promote rapid growth of new shoots and leaves.
• To aid chlorophyll production for dark green color.
• To improve overall plant health, quality and density.
• To increase tolerance to heat, cold and drought stress.

Which Source of Nitrogen is Best?

Inorganic sources may cost less per bag, but are more costly in the long run because they are not as effective and require more frequent application. Natural organic sources are more expensive and generally release very slowly. The best sources of water soluble nitrogen are urea based synthetic organics (SCU*, UF**, PCSCU***) with controlled release properties for a deep green color without unwanted excess growth.

The best fertilizer for general home lawn maintenance contains a combination of inorganic nitrogen plus SCU*, UF** or PCSCU***.

The major benefits of the synthetic organics include:

• Will not leach or burn.
• Better nitrogen availability.
• Need fewer applications.
• Long lasting, slow release.

Sources of Nitrogen: Advantages and Disadvantages

Some kinds of nitrogen readily dissolve in water, releasing nutrients to spree plant growth and green-up grass quickly. Thus, in a climate where there is a lot of rain or frequent irrigation, growth will be rapid. Other types of nitrogen react more slowly and result in longer lasting, controlled release of nutrients to the grass plants.

Phosphorus

• Promotes development of strong root structures.
• Aids in the plant’s ability to use and transfer energy.
• Stimulates growth of larger flowers and vegetables.
• Enhances winter hardiness.

Sources of phosphorus are: rock phosphorus, ammoniated phosphates, super phosphates, phosphoric acid and bone meal. Only a tiny amount of phosphate can be dissolved at any time in soil and water. One application can last for months. Thus, it is not necessary to apply large amounts of phosphorus on an established lawn.

Adequate levels of phosphorus are important for good root development when establishing a lawn from seed, sod sprigs or plugs. For best performance, apply a fertilizer high in phosphate and work into the upper 2-3 inches of soil when preparing the ground for a new lawn.

Potash (Potassium)

• Maintains salt balance and aids uptake of nutrients.
• Promotes development of thick cell walls for improved winter hardiness and heat resistance.
• Reduces damage due to drought and disease.
• Aids water uptake. Influences performance of enzymes.
• Enhances overall health and vigor.

Sources of potash are: sulfate of potash, muriate of potash, nitrate of potash and sulfate of potash magnesia.

Potassium is a soluble and highly leachable plant nutrient and must be supplied at a constant rate. Once applied it is taken up by the plant rapidly. Although not necessarily harmful, over-application is of no added benefit to the plants.
Potassium is a particularly important nutrient in Fall or Starter Fertilizers.

Micro-nutrients (Minor Elements)

The seven essential elements for plant growth include:
Boron (B) Copper (Cu) Manganese (Mn)
Chlorine (Ci) Iron (Fe) Molybdenum (Mo) Zinc (Zn)

* SCU = Sulfur Coated Urea
** UF = Urea Formaldehyde
*** PCSCU = Polymer Coated SCU