Soil microorganisms, sometimes spelled as soil micro-organisms, are a very important element of healthy soil. Knowing what microbes in soil eat, the conditions they thrive in and the temperatures that they are most active in is important in organic gardening and organic lawn care. From a practical standpoint, it boils down to organic matter, but not just any organic matter. These facts below will help you plan your activities around the time they are most beneficial. Below is a partial list of important functions they perform.
Soil microorganisms are responsible for:
Types of Microorganisms in Soil
There are several types of microorganisms in soil that benefit plants. Together they make up an immense population of living organisms. One teaspoon of soil may contain millions of various types. Below is a list of common soil microorganisms found throughout the world.
Soil microorganisms are living, breathing organisms and, therefore, need to eat. They compete with plants for nutrients including Nitrogen, Phosphorus, Potassium and micronutrients as well. They also consume amino acids, vitamins, and other soil compounds. Their nutrients are primarily derived from the organic matter they feed upon. The benefit is that they also give back or perform other functions that benefit higher plant life.
It is a variety of natural substances including decomposed leaves, grass clipping, shed roots, wood chips, etc. Humus (well decomposed organic matter) is the richest source for plant growth. Organic matter comes in many different nutrient levels, especially Nitrogen. While soil microbes need carbon (C) to live, they also need the nitrogen contained in organic matter. Therefore, the Carbon to Nitrogen ratio (C:N) is very important.
Problems with Low Nitrogen Organic Matter
Organic matter low in Nitrogen will also have a slower breakdown rate than organic matter with higher nitrogen levels. The microbes will consume the Nitrogen element first and the grass will get what is left over. So organic matter high in carbon and low in Nitrogen will provide little nitrogen to the grass. However, if another N source is applied over the organic matter, it will speed up the decomposition.
Therefore, the rule of thumb is to choose an organic matter with higher levels of nitrogen. Anything lower than four percent (4%) Nitrogen with high Carbon content should be considered a soil amendment and not a fertilizer.
How Temperature Affects Soil Microbe Activity
Soil Microbe activity is dependent on soil temperatures. For simplicity, all essential soil microbes are classified into the three different temperature ranges they are most active in.
Since the primary group contains Mesophiles, this has a great influence on the degree of soil microbe activity. Areas where the temperatures are warm most of the year, organic matter can be consumed very quickly. Tropical rainforests are so lush in part because of consistently warm temperatures, which promote fast breakdown of organic matter and the release of nutrients into the soil.
Cooler areas, such as Canada and parts of Europe, that have extended periods of cool weather below 77 degrees will benefit far less from the additions of organic matter. This is because far fewer microbes are active in that temperature range. It is possible to build unhealthy levels of organic matter if you follow the example of those in warmer climates.
The scientific rule is this: With every 18 degree rise in temperature, from 32 degrees to 95 degrees, there is a 1.5 to 3.0 % increase in microbial activity. (Carrol/Waddington/Rieke)
Remember, the food availabity to microbes, the quality of organic matter, soil types, pH level, percent of Nitrogen, etc. will also have an effect on microbial activity level.
Soil pH Factor and Soil Calcium
Most soil microorganisms can tolerate a wide range of soil levels. However, bacteria favors a neutral to slightly alkaline soil up to 8.0. When pH drops below 6, fungi begin to dominate as bacteria finds it less favorable. It is important to adjust soil pH to maintain high levels of bacteria as long as plants that are favored require neutral soil pH.
Bacteria need calcium to perform at their highest levels. As calcium becomes unavailable or lacking bacteria numbers will fall accordingly.
Consider using Super-Cal Calcium for quickly adding calcium that can benefit plants and soil bacteria from the moment it is applied. One gallon has been shown to produce the equivalent of 500 lbs of lime due to the organic acids that bring unavailable calcium into solution.
Just as temperature levels stimulate different soil microbes, so does soil moisture. Some are obvious. Persistent, damp conditions with heavy shade will promote the growth of algae while hindering microbes that thrive in sunny locations. Proper lawn watering requires deep watering so that the soil is wet 4 inches deep. Shallow watering means only the surface is wet. It drys out quickly and can greatly hinder soil microbes.
Oxygen levels necessary for healthy microbes
There is a balance to everything, including oxygen in soil. Compacted soil will have less oxygen and less water holding capacity. Clay soil consists of extremely tiny particles, even smaller than silt. Clay with proper structure can have sufficient oxygen, but it can also compact easily. Since soil microorganisms consume oxygen, but low oxygen soils will quickly deplete what oxygen it has and lower the soil microorganism levels. In lawns, deeply water to a level of 4 inches deep and allow it to dry before watering again. The deeper soil will remain moist at sufficient levels. Shallow watering means when the surface moisture is gone there is no moisture deeper to support a healthy microbe population.
Well decomposed organic matter is the oldest form of biostimulant and very effective. Modern advancements allow us to apply specific bacteria and other ingredients necessary for healthy plants. Other than organic matter, humic acid is a well performing biostimulant for lawns and gardens that has shown to stimulate soil microorganisms.
Humic acid is known to:
Soil microorganisms are one of the most important elements of a healthy soil. A good lawn care program will take advantage of the many benefits of soil microbes and the biostimulants that encourage them.
References (Turfgrass Soil Fertility and Chemical Problems - Humates/Humic Acid - R.N. Carow/D.V. Waddington/P.E. Rieke P.277)
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Soil Microorganisms back to Lawn Care Academy Home
"I sprayed Agri-Cal Calcium on the pastures, but left some parts unsprayed because I wanted to see if there was a difference. I noticed the cattle were ignoring the unsprayed parts and were eating from the pasture I had sprayed with calcium. It must have been sweeter tasting to them and clearly does work. I am very happy with it." (Via a Telephone Conversation)
Eddie L. - Trion GA
(For even more Information on how Agri-Cal can benefit your pastures, field crops, and plants, Click Here.