Understanding Organics
and Organic Lawn Fertilizer

I have received a growing number of questions concerning organic lawn fertilizer in recent years. Many people would like to include it in their lawn care plans, but may not understand what is involved.

For added difficulty, the term “organic lawn care” means different things to different people. Few concepts in lawn care can elicit such a broad range of responses. For some, organic lawn care means using only natural organic materials, while completely avoiding any use of chemical lawn products. For others, it means developing a more responsible lawn care program with the addition of a quality organic lawn fertilizer.

In any case, the term “organic matter” (O/M) becomes a chief keyword in the organic lawn care dictionary. Therefore, the purpose of this page is to give you an unbiased look at the benefits, use, and limitations of organics in lawn care.

For those considering an organic program, you should become familiar with the products that are available, along with their benefits and limitations. The advantages of using organic matter to improve soil and turf quality have been well documented. However, if your plan is to use natural organics only, without pesticides or herbicides, one should not expect a perfect, weed free lawn. No lawn is immune to weed problems and several types of broadleaf weeds are very capable of growing and spreading in quality turf. Ultimately, it will depend on what you are able to live with.

Soil organic matter and plant health

The soil is the foundation of plant growth. The concept of organics has to do with enriching the soil and increasing soil flora. In nature, nutrients enter the soil as organic matter is broken down by soil microorganisms. Therefore, the philosophy behind the use of organics in lawn care is simple. In feeding the soil, you feed the soil microorganisms, which in turn, feeds the plants.

Healthy soil is home to billions of microorganisms that feed on organic matter in the soil. Organic matter could be leaves, grass clippings, manure, buried wood, shed grass roots, or almost any biodegradable material that enters the soil. As the microbes feed on the O/M, they release nutrients in a form that plants can take up through the roots. Nitrogen is one of the elements released and the element consumed by grasses in the greatest amount. For this reason, lawn fertility programs, whether they are organic or inorganic, are based on the nitrogen needs of the grass. See Developing a Lawn Fertility Program for a better understanding of lawn fertility programs.

Both, natural organics and most synthetic organics must have microbial activity to release nutrients into the soil. In fact, soil microbes are so important to plant health, that without them, the soil is thought to be dead. In nature, plants cannot live without them.

A soil test will determine the amount of organic matter that is currently in your soil. What the soil test doesn’t tell you is how much of the O/M is consumable by soil microbes. A supply of fresh organic matter in the form of organic lawn fertilizer will keep microbe populations high and healthy.

The two basic types of organic lawn fertilizer

In the lawn care industry, there are two basic types of organic lawn fertilizer that are used on lawns: natural organics and synthetic organics.

Natural organics are materials made from natural sources such as manure, plant, animal or fish by-products. One advantage of commercial organic lawn fertilizer is that it is granulated for easy measuring and spreading. Some types come in liquid form, but liquids can be more difficult to apply evenly.

The term synthetic organic is primarily a reference to “urea”, the nitrogen source found in most synthetic organics. Urea can be altered through chemical reactions with other chemicals to produce different varieties of slow release products. The page on Nitrogen Sources can give you more information on different forms of urea. Urea is classified as an organic because it contains carbon in its structure.

Synthetic organic nitrogen can be blended with natural organic fertilizers to give it a variety of nitrogen levels and release responses. These products are referred to as “bridge products”.

Note: Synthetic organics should not be confused with “inorganic” chemical fertilizers, such as ammonium nitrate or ammonium sulfate.

An organic fertilizer for all seasons

Using organic lawn fertilizer offers your lawn an organic source of nitrogen and other micronutrients. However, the nutrient content can vary greatly depending on the type of organic matter used. You should always read the nutrient analysis to ensure it has the required nutrients to meet your grass' needs for that time of year. If the nutrient analysis is insufficient for your lawns needs, you can choose another type or you may need to supplement your lawn with an application of an inorganic or synthetic organic fertilizer.

Organic lawn Fertilizer that is high in organic matter, but low in N-P-K, can be applied in much heavier amounts. These varieties are usually labeled as summer fertilizers that typically deliver slow release forms of organic nitrogen. Summer fertilizers are extremely helpful in feeding the immense microbe populations. For most grass types, the lower nutrient content of summer organics makes it difficult to over-fertilize, even at the higher rates.

Organic lawn fertilizer developed for spring applications will often have the lowest organic matter content. A portion of the available nitrogen will be in another form. This is because most soil microbes are still inactive in early spring. Some companies offer early spring fertilizers with a pre-emergent herbicide to prevent crabgrass and other weeds from germinating.

Organic lawn fertilizer intended for fall use will have a fairly high organic matter content, but often combined with synthetic organic nitrogen sources. These are great for the higher nitrogen needs of late season cool season grasses. These fertilizers can also be used on warm season grasses during summer months.

Limitations of organic lawn fertilizer

The primary limitation of natural organic lawn fertilizer is its low nitrogen content and slow release. As stated before, the nutrients in natural organic fertilizers are released slowly through microbial activity.

Soil microbe activity levels are subject to soil temperatures with the highest activity in mid-summer. Therefore, it stands to reason that the heaviest amounts of organic fertilizer are applied in late spring and summer. As soil temperatures begin to drop in the fall of the year, so does the level of microbe activity. A fact not often explained to homeowners is that you cannot expect the grass to have any reaction from organic lawn fertilizer that depend on microbe activity, when soil microbes are not active.

The limitation of low nitrogen content can affect many grass species that require higher nitrogen levels. Bermudagrass, for example, requires as much as 8lbs of nitrogen per year. If the organic material can’t deliver enough nitrogen to sustain the needs of the grass, then it will suffer. Nitrogen is an essential element needed for chlorophyll and energy production as well as other functions within the plant. The first visible sign of a lack of nitrogen is a condition called chlorosis. This is a yellowing of the grass from a lack of chlorophyll production.

Many cool season grasses require fertilizers with the highest nitrogen content to be applied in the fall. In fact, the highest percent of nitrogen in a single application is applied after the last mowing of the year. The lower nitrogen content of natural organics combined with the lower microbe activity of rapidly cooling soil temperatures could prove to be problematic for nitrogen hungry grasses. It is during these times that bridge products excel. You will get a higher percent of nitrogen using a synthetic organic nitrogen source that is blended with a premium source of organic matter.

Using compost to modify your soil

Soils with poor structure will be improved significantly with the additions of compost. Compost can be purchased or homemade and is used when larger volumes of organic matter is needed. Where organic lawn fertilizer is used for immediate grass needs, compost is used for altering soil structure. The methods and rates of application will depend on how the materials are used and the nutrient analysis of the compost.

Coarse-textured soils are those high in sand. Adding organic matter to sandy soil will help with water retention and provide additional nutrients. Organic matter traps many chemicals and slows leaching of unused nutrients. For extremely sandy soil, a mix of soil to organic matter as high as 50/50 may be needed.

Fine-textured soils will be high in silt or clay. These soils tend to hold water well and can become waterlogged in heavy rains. Fine textured soils also compact easily, preventing air and water from reaching the roots. As a result, high traffic areas will often have very thin grass or no grass at all. The addition of organic matter worked into fine-textured soil will have immediate benefits. This is also a common problem in new home construction where the topsoil is removed.

Adding O/M to correct serious soil problems

If the soil is in need of compost and has not yet been planted, roto-tilling compost into the soil will offer the fastest results. If the lawn is over 50% weeds, you can kill all the grass and weeds using Round-up (glyphosate) or an equivalent, and then roto-till the organic matter into the soil. Try to reach at least 6 inches deep when you till the soil, if possible. Of not, then till as deep as you can. You will need to be careful to level the lawn and use a lawn roller on the soil after roto-tilling.

If roto-tilling is not a good option, there is another method. For established lawns, you will need a core aerator. First, heavily aerate the lawn, going over the lawn several times. Core aeration pulls out plugs of soil that are 2 ½ to 3 inches long. After aerating, remove the plugs that were pulled out, then spread a ½ to 1 inch layer of compost over the lawn. Care should be taken to fill in the holes. You may have to do this a few years in a row for soils with excessive clay. The page on Understanding the Soil Analysis Report has additional information on organic matter.

Organic compost also has great disease suppression abilities. However, it must be comprised of the right materials. Manures, food products and lawn and agricultural wastes make good disease fighting materials. For a better examination of what it should include along with other important information, please read the section on Organic Composts.

List of benefits at a glance

The list below offers a quick look at the benefits of using organic lawn fertilizer or applying composted organic matter to the soil.

  • Compost that is worked into the soil will elevate the soil’s "Cation Exchange Capacity" (CEC). In soil science, the CEC has to do with the soil’s ability to retain nutrients. This is especially true for low CEC soils such as soils high in sand.
  • Organic matter increases the water retention of coarse soils (sandy) and aids in the downward movement of water through fine soils (clay/silt).
  • Compost amended soils help resist compaction in high traffic areas.
  • Organic matter adds several micronutrients not often supplied in inorganic fertilizers.
  • Organic matter encourages the growth and reproduction of macroorganisms such as earthworms.
  • Lawns receiving regular application of organic lawn fertilizer have fewer problems with certain lawn diseases. With the addition of O/M, there are healthier populations of beneficial microbes that feed on pathogenic fungi in the soil.
  • Organic matter typically has a neutral or near neutral pH. If you have slight pH problems, before correcting it, first add the needed organic matter. The organic matter may correct the soil problem.
  • Organic matter absorbs and traps pesticides and other chemicals applied to the soil. The microbes that feed on the O/M also breakdown most lawn chemicals.

This is important to know. In the professional industry, it has been a practice to apply compost to contaminated ground as a means of cleaning the soil. It is a process called “bioremediation”. Certain types of organic matter are better suited for this than others. One example is compost made from sewage sludge. Sludge from water treatment plants has been observed to have this cleansing effect.




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