Fertilizers

Plants need 16 essential nutrients to grow. Carbon, Oxygen, and Hydrogen are absorbed from the air and water while all the rest come from the soil. Most nutrients are used in very small amounts so they are generally available to plants from the natural breakdown of both organic material and mineral components in soil. People use either synthetic fertilizers or organic ones such as compost to improve soil fertility.

Plants consume three nutrients from the soil in large quantities; they are: Nitrogen, Phosphate and Potassium. These important nutrients are depleted by common gardening practices such as cutting down the plants and sending the garden waste to the City compost during fall clean up instead of recycling them into a backyard composter for later use in the garden soil.

Fertilizers always have three numbers on the package; these numbers refer to the amount of Nitrogen, Phosphate and Potassium available to the plant in the package. This is a standard method for representing the nutrient content for both synthetic and organic fertilizers. All fertilizers regardless of their origins will list the available Nitrogen, Phosphate and Potassium in this order. If a nutrient is not included, the package will have a 0 in its place

For example a package with the 10-25-10 will have 10% Nitrogen, 25% Phosphate and 10% Potassium. On the other hand if it is a box of blood meal it will probably have 12-0-0 which means that the bloodmeal will have 12% Nitrogen, 0% Phosphate and 0% Potassium.

Nitrogen (N)
The leaves, stems and roots need a large amount of Nitrogen for lush green growth. Nitrogen is easily lost from the garden by leaching with water or escaping from the soil as a gas.

Deficiency Symptoms
There will be a uniform yellowing of the leaves that starts in the old leaves. The plant moves Nitrogen from the old leaves to make new leaves and tips. The stems will be thin and spindly.

Over Abundance Symptoms
The plant will have rapid bright to dark green lush growth. It will be weak because the cells are growing too quickly. The plant will be susceptible to insect and disease damage because of the weak cells. Nitrogen abundance also delays or reduces flowering and fruiting.

Phosphate (P)
Phosphate is needed for root growth, flowering, fruit and seed development. It is used for cell respiration (metabolizing sugar and starch to release energy), and cell division in the rapidly growing tips of stems and roots.

Deficiency Symptoms
The plant will have stunted growth and dark green leaves. The old leaves lower on the stem may become purplish between the veins. Delayed maturation, few flowers and poor seed development are further symptoms of deficiency.

Deficiencies occur when the soil pH is not near neutral (pH 7) because the Phosphate becomes bound to Iron and Aluminum in acidic soil and it binds with Calcium in alkaline soils. Organic matter and humus bind with Iron and Aluminum in the soil insuring that the phosphate is available to the plants.

Over Abundance Symptoms
Not normally a problem.

Potassium (K)
Potassium is needed for flower, fruit and leaf production. It increases a plants ability to withstand environmental stresses. It improves winter hardiness, heat and drought tolerance, resistance to fungal infections and insect damage. Potassium is found in abundance in the growing tips of plants because it activates enzymes, it regulates the movement of fluids through the cells and through the plant. It is involved in the manufacturing and metabolism of sugars, so it is essential for plant growth.

Deficiency Symptoms
Leaves yellow from the edges to the centre. Older leaves become mottled. Potassium stops lodging of stems (they suddenly snap off with no apparent reason). Clay and organic matter/humus in the soil retain Potassium.

Over Abundance Symptoms
Plants can take up excess quantities without benefit or harm; this is referred to as Luxury Consumption. For this reason it is best to apply it in small quantities, frequently if it is needed.

Chemical/Synthetic Fertilizers are manufactured.

• The Nitrogen is extracted from the atmosphere (which is 78% Nitrogen, 21% Oxygen and the remaining 1% is composed of Carbon dioxide and other gases). The Phosphate and Potassium are derived from rock that is refined.
• Chemical fertilizers are the most widely used fertilizers used today because they are easy to use, inexpensive and easily absorbed by the plant. They come in liquid or dry forms. Unfortunately, excess nutrients leach into the water through runoff into the sewers causing contamination and eutrophication (death) of lakes and streams endangering the fish and amphibians.
• Chemical/synthetic fertilizers feed the plant but not the soil. Over time there is a gradual decrease in organic matter in the soil, as it is used up, and the soil becomes compacted. The lack of organic matter leads to a reduction in soil organisms making it more susceptible to insect or disease infestations.
• Chemical/synthetic fertilizers are applied many times during the spring, summer and fall, according to the package instructions.

Organic Fertilizers include compost, manure, and fish, bone or blood meal.

• They are slow release because they must decompose before the nutrients are released. They are bulky, take effort to apply, and the nutrient content is low.
• Fortunately they improve the tilth of the soil making it more porous, giving it better water drainage and water storage. They improve the storage of all nutrients thereby reducing the rate at which nutrients leach into the waterways. They also supply micro-nutrients needed for plant growth, and feed the earthworms and other organisms that live in the soil.
• Organic matter dug into the soil or applied annually as topdressing or mulch material is the best way to insure that the soil is a healthy growing environment for plants.
• There are organic lawn fertilizers available that are formed into pellets for easy handling that are applied to the lawn once a year in the early summer.

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