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Comparing Organic Lawn Fertilizer with Chemical Fertilizers

Are natural organic fertilizers safer than chemical fertilizers? Are they better for your lawn, family and the environment?

Ideally soils will support plant life - but this is not usually the case. We fertilize because soils lack the elements to support plant growth. Natural organic fertilizer, manufactured organic and chemical fertilizers all serve the same purpose - to provide nutrients needed by plants to sustain healthy growth.

There is a lot of debate and confusion over the best type of lawn fertilizer. The type you use makes no difference to your grass. All types have advantages and disadvantages and when properly used are safe for lawns, the environment and involve few risks to humans or other animals. To be used by grass, all nutrients in fertilizers - no matter the source - must be broken down into the same chemical form (listed in the table below).

Organic vs. Chemical Fertilizers
Fertilizer becomes a pollutant when it is misapplied or overapplied - it does not matter if the product is natural organic or synthetic. Take care to use fertilizers according to their labels and instructions. Proper rate and timing is important as well as basing lawn nutrient requirements on a reliable soil test. Protect our water sources! Avoid getting fertilizer on sidewalks, driveways and roads where it can wash into storm drains and then into streams, lakes and rivers.

There are 16 essential elements needed by plants to grow (see the table below). Carbon, hydrogen and oxygen are available to plants from air and water. The other 13 elements are supplied to the plants from the soil. Fertilizers supplement the soil with these needed nutrients.

The 13 mineral elements found in soils are grouped according to amounts found within plants - macronutrients, secondary nutrients and micronutrients. Nitrogen (N), phosphorus (P) and potassium (K) - the macronutrients - are the three main nutrients in fertilizer and needed by plants the most. The secondary and micronutrients are essential but in very small amounts.

16 Elements Essential For Plant Growth
Element Symbol Form Available to Plants
Source: Air and Water
Carbon C CO2
Oxygen O O2 and H20
Hydrogen H H2O
Source: Soil - Macronutrients
Nitrogen N Nitrate & Ammonium NO3-, NH4+
Phosphorus P Phosphate H2PO4-
Potassium K Potassium K+
Source: Soil - Secondary Nutrients
Calcium Ca Calcium Ca++
Sulfur S Sulfate SO4=
Magnesium Mg Magnesium Mg++
Source: Soil - Micronutrients
Manganese Mn Manganese Mn++
Zinc Zn Zinc Zn++
Boron B Borate H2BO3-
Copper Cu Copper Cu++
Iron Fe Iron Fe+++
Molybdenum Mo Molybdate MoO4=
Chlorine Cl Cloride Cl-

There are hundreds of companies that claim their products will improve your soil and make your lawn more vigorous and healthier than their competitor's brand. So how do you choose the best lawn fertilizer?

Nutrient release rate and cost of actual nutrients per pound are important factors to consider.

Chemical fertilizers with fast nutrient release rates provide nutrients in forms that are highly soluble and available to your lawn. These products must be used carefully. They will stimulate quick growth, must be applied at low rates and frequently, will burn your grass when over applied and are likely to leach nutrients into groundwater.

Natural organic fertilizers release nutrients slowly. As the soil microorganisms decompose the organic matter, the nutrients are converted into the chemical forms that are available to plants. Higher application rates may be applied, they have a low burn potential and will last longer.

Chemical fertilizers are also available in slow-release formulations that release nutrients by water penetration, weathering or microbial action.

Since the purpose of fertilizing is to provide essential nutrients to assist plant growth, it makes sense to consider the cost of the actual nutrients in the product you are purchasing.

Fertilizer Analysis - the concentration of nutrients by percent - is printed prominently on the the product label. The analysis is always printed in a three number sequence indicating the amounts of N - P - K. An example is 23-3-6, indicates 23% Nitrogen, Phosphorus equivalent to 3% P2O5, and and Potassium equivalent to 6% K2O.
Spreading Organic Fertilizer

Ultimately it is up to you to decide what is best for your lawn based on the advantages and disadvantages of each.

Advantages of Natural Organic Fertilizers

  • They are made from renewable resources and recycled materials.
  • Add organic matter to the soil - improving physical nature of the soil.
  • Feed beneficial soil microbes, increasing their activity.
  • Slow nutrient release rate - high application rates may be applied that will last longer than chemical fertilizers...meaning less applications per year.
  • Less nutrient loss from poorly timed applications.
  • Very low potential to cause salt damage - "burn".
  • Contains micronutrients.

Disadvantages of Natural Organic Fertilizers

  • Relatively low concentrations of actual nutrients - low nutrient analysis compared to synthetic products.
  • Require larger volumes of product per application
  • They are expensive - pound for pound of actual nutrients are higher than synthetic products.
  • Depend on warm temperatures and soil microbe activity to work - slow repsonse in cool soils.
  • Exact content of nutrients is often unknown.
  • Homeowners often misjudge application rates due to large volume needed...meaning they don't spread enough product.
  • Composts and manure often contain weed seeds.
  • Organic residues that have a low nitrogen content can cause nitrogen deficiencies in plants as microorganisms decompose the organic compounds.

Advantages of Manufactured Organic and Chemical Fertilizers

  • Less expensive than natural organic products.
  • Labeled with the specific amount of nutrients contained in the package - easy to calculate proper rates.
  • Contain higher nutrient concentrations - meaning less product required to handle and apply.
  • Spreads easily in liquid or dry forms.
  • Fast-release nutrients available to plants in any weather.
  • Slow release formulations are available (For example - sulfur coated urea & IBDU).
  • Allow turfgrass managers to spoon feed precise doses of nutrients and can be custom-made for your requirement.

Disadvantages of Manufactured Organic and Chemical fertilizers

  • They are normally made from petroleum or natural gas - some are made from naturally occurring mineral deposits.
  • Fast release nutrients are prone to leaching and have a high burn potential.
  • Fast release chemical fertilizers have high potential to leach nutrients into ground waters.
  • Chemical fertilizers require more applications per year than organic fertilizers.
Organic vs Chemical Fertilizers


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