Potting soil vs topsoil – Differences + Which to use for Grass

Potting soil and topsoil are popular types of dirt in gardening. So, what is the different between potting soil and topsoil? Which one is better for grass?

Potting soil is a mixture of dirt, peat moss, organic matter and nutrients important for container gardening. On the other hand, topsoil naturally formed through slow weathering of rocks and decaying organic matter over a long period of time.

Potting soil vs Topsoil – Differences

Potting soil and topsoil differs in terms of composition, Application, longevity and characteristics.

1. Composition

Composition is among the main differences between potting soil and topsoil. Potting soil can be soilless or contain soil. It’s commercially manufactured to meet certain plant requirements. It usually contain various ingredients.

Some of them may include: garden soil, amendment materials like peat moss or coconut coir, organic matter like composted sawdust, fertilizer and other materials like perlite or vermiculite to improve its drainage. However, these ingredients may vary depending on the purpose of the potting soil.

On the other hand, topsoil is made up of natural garden soil that is rich in different nutrients. It may contain materials like clay or sandy soil, compost manure and other decaying organic matter. These ingredients may vary depending with soil and climatic conditions of your region.

2. Application

Potting soil that contain soil is ideal for growing vegetables outdoor either in large pots or raised bed. On the other hand, soilless potting soil is better for indoor plants like fern or cactus. It’s well aerated and drained to support healthy growth of your plants.

There are different types of potting soil that are commercially produced to suit various plants. They usually contain different materials to suit the needs of intended plants. For instance, a potting soil designed for succulent plants contain sandy soil and other amendments to improve drainage.

With topsoil, it is more of a soil conditioner than a growing medium for plants. It’s usually used for improving flower bed soil, enriching the existing garden soil, increasing the volume of raised bed soil and filling dirt or other debris when starting a new garden.

If you are intending to use topsoil when starting a new lawn or for vegetable cultivation, you should mix it thoroughly with native soil to improve aeration, drainage and nutritional content.

Topsoil is not ideal growing medium due to its poor structure. It has poor drainage that can lead to excessive water retention and poor roots development. Clay or sandy topsoil require some amendments such as organic matter to support growth of plants

3. Longevity

Longevity also differentiates between potting soil and topsoil. Unopened bags of potting soil can last for six month only. Storing it for more than this duration will degrade its quality.

Potting soil in containers will start to degrade after two years. It’s therefore, it’s ideal to replace potting soil in pots or containers after one or two years.

The quality of ingredients used for making potting soil will start to degrade in two years’ time. For instance, peat moss in potting soil will decompose fully within a period of two years. Therefore, it’s best to refresh the old potting soil in containers with 50% fresh potting soil.

With topsoil, it last longer than potting soil. Bagged topsoil can last up to 8 years when stored properly. However, it require some amendments prior to use. Adding fertilizer or compost will help to improve drainage and its nutritional content.

4. Characteristics

A true potting soil is soilless, light and fluffy. It provide suitable growth conditions for container gardening. It has soil amendments to improve drainage, aeration and its nutritional value. Potting soil is sterilized during production process and does not contain bacteria, fungi or weed seeds that may attack your plants in their initial growth stage.

With topsoil, it is coarse and heavy due to clay, sand particles, composted organic matter and other materials. It also contain soil microbes that are beneficial to your plants. Although topsoil is fertile, its poor drainage and aeration can prevent healthy growth of plants when not amended.

Will Grass Grow in Potting Soil?

Yes, grass can grow in potting soil. However, it is not ideal for outdoor plants such as grass. Potting soil is best when intending to grow your plants in containers. It is best for planters, hanging baskets, window boxes and other containers where drainage and weight may be a problem.

Potting soil is ideal for plants that require well drained and aerated soil. It allow excess water to drain out from bottom of containers through gravity. It pulls in air to replace the drained water. Plants breathe through roots. Therefore, they require well aerated growing medium.

Potting soil is carefully mixed with other ingredients to improve drainage, aeration and nutritional content. In most cases, it’s usually mixed with peat moss, composted organic matter like sawdust and other materials.

Peat moss is the main ingredient that is used in making potting soil. The other ingredients are added to make it ideal for certain plants use. For instance, potting soil for seed starters are made up of fine particles to encourage fast development and spread of the initial roots.

Between Potting and Topsoil which is good for grass

Topsoil would be the best choice over potting soil when choosing one for your grass. Topsoil provides a deep root development medium for a natural lawn grass. It also provide healthy germination and growth of grass.

If your garden soil is not working for your grass as a result of overuse of fertilizers or compaction, you may be required to buy topsoil. Put the topsoil in your garden and conduct a soil test to determine if other amendments are needed.

You may need to add organic matter like compost to improve drainage and aeration. It’s also important to adjust the pH. Incorporating your existing garden soil with a few inches of topsoil will give your grass a better chance of establishing roots properly and growing healthy.

Topsoil is also much cheaper since it’s sold in bulk and can be used in different ways prior to planting your grass. For instance, you can use it to level your lawn by filling old ponds and repairing cracks in your yard after a heavy rainstorm related erosions.

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