Soil Sterilization Techniques, Ideas, Tips

Soil Sterilization Techniques, Ideas, and Tips

Today, we talk about “Soil Sterilization Techniques and Process”.

What is soil sterilization? Sterilization of soil is the act of killing or destroying the action of diseases causing organism that is present in the soil without causing harm to other plants. In other words, soil sterilization is a procedure by which chemicals are used to render soil living organism that is capable of destroying plants and causing disease in the soil to be inactive, impotent or unproductive. These chemicals are selective in nature, that is, when they are used, they affect particular diseases for which it is meant for, without causing harm to the other organism that inhabits the soil.

Numerous ways of soil sterilization have been used to sterilize the soil or inhibit microbial activities in the soil. Sterilization generally alters the chemical and physical properties of soil in addition to eliminating organization. The importance of soil sterilization is to create ideal conditions necessary for plant growth and development in the soil. The death of these microorganisms due to sterilization helps to free certain nutrient to the plant such as nitrate which increases plant growth. If you are a gardener or farmer, you should know the importance of soil sterilization techniques.

Soil sterilization techniques of the garden soil:

Different techniques of sterilizing the garden soil will be discussed below;

  • Sterilizing garden soil is more difficult than sterilizing potting soil. Solarization is the best procedure to sterilize garden soil.
  • In order to sterilize the garden soil, you have to follow a procedure called solarization, which means using the solar heat to sterilize the soil. This can be best done in the summer and particularly on a dry and sunny day.
  • Normally, the organism beneficial for the soil survives the process of solarization as it only affects the harmful elements in the soil, so you do not have to worry about the diminishing quality of the soil.
  • Planning to do solarization through the summer means you have to plan right from the winter before. In winter, you have to cover the area with black plastic or can also plant some plants to increase the fertility of the soil. In spring plant new saplings. Does remember to remove the black plastic before start planting.
  • It is easier to sterilize potting soil than garden soil. In the case of topsoil or potting soil, you can use a conventional oven or a microwave oven to sterilize the soil. You want to set the temperature of the oven at 210-250°F, and then put the soil in it, in a container that is protected to be used in the oven. Maintain the soil in the oven for 30 minutes. Alternatively, you can use a microwave oven for this purpose, and you have to heat the soil for 30 seconds at full power.
  • You can sterilize the soil with steam. This is considered the best possible process for sterilization of soil. You can also use a pressure cooker for this purpose too.
  • The above are the main techniques of sterilization of the soil. However, in general soil doesn’t need sterilization, and you must only sterilize if you have harmful fungi and such other things causing harm to your plants.

Sterilize Potting Soil

The sterilization of the potting soil process will be discussed below;

Preparing Soil for Sterilization:

Soil Consistency: The soil needs to be moist enough to compact into a ball, but must crumble when pressure is removed. This can be done by basically packing a ball of soil between the hands. Add a little water and mix consistency is met.

Placing soil into the pan: Place the soil into a roasting pan or in a baking sheet. Evenly distribute the soil in the pan & break up any clumps. Do not fill to the edge of the pan, and keep depth under four inches deep. Cover the pan or baking sheet tightly with aluminum foil. The foil needs to be tight and secure to avoid moisture loss and burning of the soil. Poke a hole in the center of the foil that is large sufficient for a meat thermometer to fit through.

Sterilizing soil:

Beginning sterilization: Put the tray into an oven and set the oven to a low temperature. The ideal temperature for sterilization is 180°F. Temperatures over 180°F may cause burning. Burning the soil will chemically vary the composition of the soil. Soil that is burned or the soil overheated will harm plants.

Baking time: The soil needs to stay in the oven for 30 minutes, while the temperature needs to remain closely around 180 degrees Fahrenheit. Check the thermometer and adjust the oven temperature as needed. Paying close concentration to temperature fluctuation is a must.

Cooling and using soil:

Cool down: After baking for 30 minutes, remove soil from the oven and let stand until the soil gets to room temperature. Slowly lift a corner of foil to allow heat to escape. The escaping steam will be hot and can burn skin.

Usage: The soil can be removed from the pan and used it has reached room temperature. Sow seeds, no deeper than four times the diameter of the seed. Water the sterilized soil with a avoid flooding the soil. Seeds are sown into a container covered with plastic wrap and placed in a cool room. Avoid sunlight until germination. Slowly introduce light over several day periods and remove the plastic wrap once germination begins.

Soil sterilization ideas:

Here we have discussed different methods of soil sterilization; they are,

Steam method:

Steaming is considered one of the best ways to sterilize potting soil and must be done for at least 30 minutes or until the temperature reaches 180°F. (82°C.).

In soil sterilization, steam method or autoclaving is generally used to sterilize soil samples as the equipment is readily available in most research and teaching laboratories. Soil is steamed at 121°c for a minimum of 20 to 30mins but normally longer than one hour. The length of time must be increased when a larger amount of soil is sterilized. The normal soil can be autoclaved in glass beakers, glass Petri dishes, and stainless steel trays with lid jar. The container used for this action can be covered with aluminum foil. The soil must be spread out in thin layers to allow for penetration of steam during the autoclave cycle.

Sterilization by heat:

Most pests, diseases, and weeds in vegetative and seed form have a temperature at which they are organically destroyed, the same being true of micro-organisms. The boiling point of water is 100°C (212°F) and it is neither practical nor desirable really to exceed this. It is in this temperature range that most sterilization processes work, fungal and virus diseases will show that such a temperature range is highly effective. Indeed, many of the weaker parasitic diseases are destroyed at temperatures as low as 54 to 60°C; but many virus diseases need fully 92°C to be completely destroyed, the same being accurate of the eelworm cysts Globodera rostochiensis.

One of the greatest problems when applying a heat procedure to soil or growing media is achieving a uniform temperature throughout the bulk. It merely requires the center of a lump of soil to stay at low temperature for it to act as a potent source of re-infection in the sterilized area of the growing medium. Over-sterilization raises problems of sterility and formation of toxic substances. Obviously too it is undesirable to incorporate doubtful bulky organics, particularly farmyard manure, until they have been sterilized although it is common practice not to sterilize them. The moisture content of a growing medium will greatly change the passage of heat and the degree of penetration achieved in a given time.

Sterilizing soil with an oven:

You can also use the oven to soil sterilization. In the oven, put a quantity of soil (about four inches deep) in an oven-safe container, like a glass or metal baking pan, covered with foil. Place a meat (or candy) thermometer into the center & bake at 180-200°F for at least 30 minutes, or when soil temp reaches 180°F. Anything higher than that can generate toxins. Take out of the oven and allow to cool, leaving the foil in place until ready to use.

Microwaves cause water in the soil and cells to absorb heat, which effects in high temperature that kills the soil organism. For this cause, the lethal action of microwaves is higher in moist soil than that of dry soils.

Seed germination:

The soil has been sterilized by heat speeds up the decomposition of organic matter in it, resulting in a more airy tilth. This non-compacted soil arrangement is ideal for seed germination. Once seeds are sprouted, roots can develop freely downward and stems are able to easily emerge upward. The lack of weeds allows the seeds to thrive without competition for nutrients.

Chemical method:

Chemical methods of sterilizing soil include the following;

Sodium oxide (NaN3)

Gaseous chemicals

Mercuric chloride (Hgcl2)

Formaldehyde or formalin method:

For soil sterilization commercial formaldehyde or formalin is diluted with water. Success depends on the penetration of the dilute solution to each particle of soil at the requisite depth, its retention in the soil for an adequate length of time and careful clearance of the fumes before potting or planting begin. Since soil does not absorb formaldehyde appreciable. It will penetrate as far as the water that carries it. Thus, a large quantity of water must be used to carry the formaldehyde well down into the subsoil. Approximately speaking, a heavy soil requires twice as much water as a light one; too wet it to a given depth. Penetration is made sure by seeing that the soil is loose, friable and moist (potting condition). Formaldehyde must not be used when the soil temperature is 40° F. or less. Retention is approximately inevitable since the fumes are given off slowly (especially in winter) and consequently act over a long time.

In some cases, covering the soil can be beneficial. They are;

  1. For soil sterilization commercial formaldehyde is diluted with water to add formaldehyde is sprayed in the total area of the field or onion plot.
  2. And the field is covering with the help of polythene paper. 

Soil sterilization tips:

Well Sterilized Soil.
Well Sterilized Soil.

Some of soil sterilization tips are given below;

  • Containers want to be sterilized before the newly sterilized potting soil can be added. Soil-borne diseases, fungi, and insects can live on small amounts of soil and debris remaining in before used and uncleaned containers.
  • It creates ideal conditions essential for plant growth and development in the soil.
  • The death of these microorganisms due to sterilization helps to discharge certain nutrient to the plant such as nitrate which increases plant growth.
  • Sterilization of the soil leads to high quality in marketing produce.
  • Soil sterilization reduces the population of microorganism that is damaging to the crop plant.
  • Reusing potting soil is fine when using with mature plants, while new seedlings or bedding plants require sterilized to have the best chance to thrive.
  • Don’t use dirt straight from the garden for a potting medium; mix it with other ingredients to create it lighter and more beneficial for your plants.
  • Make sure that potting containers themselves are clean since they can harbor disease organisms. You can wash the containers in bleach and water solution.

That’s all folks about soil sterilization techniques and tips.

Read: Homemade Organic Fungicides for Plants.


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