Properties of Ideal Soil and Potting Mixtures

Gardening Basics
// December 15, 2017
properties of soil

Many plant growers often ask what kind of soil or potting mixture should be added to a pot of indoor plants? What is the ideal potting mix? Are the properties of ideal soil or potting mixture measurable? Well, it turns out that physical and chemical properties of ideal soil and potting mixture are measurable. Let’s have a look at some important ones:

best soil for potted plants

Physical properties of an ideal potting mixture:

The essential physical properties of potting soil vary with intended use. A soil that is excellent in a field may be entirely unsatisfactory in a pot. Following are some important physical properties of soil and potting mixtures:

1. Bulk density:

Bulk density expresses soil weight (grams per cubic centimeter) and takes into consideration solid and pore spaces between particles within a volume. The bulk density of 0.5 to 0.75 g/ml is best for fully grown container plants.

2. Pore space:

Pore space of a field soil or potting mixture is an important measure of its suitability for growing foliage plants. Foliage plant growth is often reduced, and sometimes plants are killed because of poor aeration caused by compaction, and over watering of potting soil with inadequate pore space.

The total pore space should be 5-30 % while non capillary spore space should be 5-10% or more in potting mixtures. Excessive pore space is not desirable, since it indicates the low water holding capacity and causes more rapid drying of soil or potting mixes.

3. Water holding capacity:

This is the ability of soil or potting mixture to hold water against the pull of gravity. Water holding capacity is measured as a percent of dry weight or percent of the volume of water contained after gravitational drainage. Water holding capacity of potting mixtures should be in the range of 20 to 60 % by volume, provided 5 to 30 % pore space is present after drainage. Buy watering tools online in India.

watering soil to check water holding capacity

4. Texture:

Texture of the potting media is determined by the particle size of components, i.e., clay, sand, and silt and it should be moderate. Texture also depends on the amount of soil fewer media and soil conditioners added in the potting mixture, e.g., cocopeat, peat moss, perlite, compost, etc. For ideal texture, no ingredient should be added in disproportionately high quantity in a given potting mixture.

Chemical properties of the ideal potting mixture:

Chemical properties of soils and potting mixes have direct effects on production cost and quality in foliage plants. Following are some essential chemical properties taken into consideration:

1. Carbon-nitrogen ratio (C/N ratio):

The C/N ratio indicates the amount of carbon present in the soil or amendment relative to nitrogen. Higher the C/N ratio more the nitrogen is required. Competition for available nitrogen between microorganisms and plants can cause nitrogen deficiency. C/N ratio of 1:50 to 1:200 is suitable for potting media.  Material with high C/N ratio can be composted for 2 to 3 months with 8 kg of nitrogen per cubic meter of material.

2. Cation exchange capacity (CEC):

CEC refers to an ability of soils or potting mixtures to retain fertilizer ions against the leaching effect of water and to release them for plant growth. Organic materials are usually high in CEC and provide buffering action against rapid changes in nutrient availability and pH. Materials with low CEC require a more frequent application of fertilizers. CEC range between 10 to 100 milliequivalents per 100 cubic centimeters is satisfactory for grown container plants.

3. pH:

Most indoor plants should be grown in media having pH range of 5.5 to 6.5, which is slightly acidic. Read about soil pH & its effect on plant growth.

4. Soluble salts:

The soluble salts in ideal soil or potting mixtures should be less than 500 pp. A typical home gardener need not worry about counting and measuring all these properties in their potting soil. It is a good idea to rely on experts opinion and purchase the ideal products from trusted sources.

physical properties of soil

By considering all the factors mentioned above, following are some of the best potting mixtures for container gardening at Ugaoo.com

  1. Gardenia garden soil mix: For flowering and fruiting plants.
  2. Gardenia Pot-o-mix: For Indoor foliage/flowering plants.
  3. Gardenia organic veggie mix: For container-grown vegetables, microgreens and herbs.

permeability of soil

Read more about What’s Inside Your Regular Pot?

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