Gardener’s Guide to Mixing Topsoil with Compost

Mixing Compost and Topsoil

For new gardeners and landscapers, combining topsoil with compost is essential for improving plant health, yet many beginners struggle to achieve the right balance, resulting in poor growth. This article provides guidance on topsoil, compost mixing ratios and practical applications.

Combining quality topsoil and compost improves soil structure, nutrient availability, and soil temperature, creating an ideal environment for a healthy garden. A USDA study reveals that compost-enriched soil has superior water retention capabilities, allowing it to hold up to 20% more moisture, which is essential for plant health during dry spells. This blog will equip you with the knowledge to cultivate thriving gardens, whether for vegetable gardens, flower beds, or new lawns when mixing topsoil with compost.

What is Topsoil?

Topsoil is the uppermost layer of soil, typically 5 – 10 inches or 10 to 25cm deep, and is crucial for plant growth. Formed over thousands of years through natural processes like weathering and decomposition, quality topsoil is rich with essential nutrients and microorganisms.

This fertile layer supports various plant life, making it essential for gardens and lawns. Its dark colour is due to its organic content, which is teeming with life, including earthworms and beneficial bacteria that enhance soil fertility.

What is Compost?

High quality compost is nutrient-rich organic matter created through the decomposition of plant and animal materials making it a fantastic natural fertiliser. This composting process involves breaking down garden waste, and other organic materials through microorganisms and worms, resulting in a dark, crumbly substance that improves soil health.

There are several types of compost:

  • Hot Compost – Made from a mix of green (nitrogen-rich) and brown (carbon-rich) materials, processed at high temperatures for rapid decomposition.
  • Cold Compost – Decomposes more slowly and requires more time.
  • Worm Compost – Created through vermicomposting using earthworms to break down organic waste.
  • Mushroom compost – nutrient-rich material from mushroom farming byproducts that enhances soil structure, improves water retention, and provides essential nutrients, all while being virtually odourless!
  • Manure – introduces beneficial microorganisms that improve nutrient cycling, suppress pathogens, and promote a healthier soil ecosystem.

Compost improves soil structure, the ability to absorb water, and provides a slow-release source of nutrients while suppressing soil-borne diseases. By incorporating compost, you can create a fertile environment that supports vibrant plant life and improves existing soil, without the use of chemical fertilisers.

Mixing Topsoil with Compost

Blending topsoil with compost is an effective strategy for gardeners. Key benefits include:

  • Nutrients in compost are readily available for plant uptake.
  • Compost and topsoil improves aeration and drainage, preventing soil compaction while leaving a neutral ph.
  • Compost boosts water retention of existing soil – great for new garden beds.
  • Microbial life in compost helps suppress soil-borne diseases.

This perfect blend of topsoil and compost is versatile, suitable for garden beds, flower or vegetable gardens, and new lawns.

Essential Tools:

  • Shovel or Spade – For digging and mixing the soil.
  • Wheelbarrow – To transport materials.
  • Garden/ Leaf Rake – For levelling the mixture and breaking up clumps.
  • Measuring Container – To ensure correct ratios of topsoil to compost.
  • Tarp or Container – To hold the mixture.

With these tools in hand, you’re prepared to create a rich soil blend for successful gardening, whether you’re starting a new garden bed or establishing a lawn. This combination will help ensure your plants thrive and your outdoor space flourishes.

Potted Plants

Topsoil compost forms a well-draining, nutrient-rich growing medium. To prepare it, mix 1 part compost with 3 parts topsoil, filling pots to a depth of 6 to 8 inches. Water regularly, and consider applying a balanced fertiliser every few weeks throughout the growing season to support healthy plant growth.

Vegetable Patches

Mixing compost with topsoil enhances vegetable patches by providing essential nutrients and stability. For the best results, use a ratio of 1 part compost to 2 parts topsoil, ensuring a minimum soil depth of 12 inches. Water regularly to keep the soil consistently moist without becoming soggy, and apply mulch to retain moisture and improve soil structure.

Flower Gardens

Mixing compost with topsoil is an excellent way to enrich vegetable patches by adding essential nutrients and improving soil stability. For optimal results, use a 1:2 ratio of compost to topsoil, ensuring the soil depth is at least 12 inches. Water the mixture regularly to maintain consistent moisture without oversaturating it, and apply mulch to help retain moisture and enhance soil structure.

Trees and Shrubs

Incorporating topsoil and compost improves the soil for trees and shrubs while helping to suppress weeds. For a balanced nutrient mix, use a ratio of 1 part compost to 3 parts topsoil. When planting, dig a hole that is 2 to 3 times wider than the root ball. After backfilling, water deeply, allowing the soil to dry slightly between watering sessions.

Turf and Lawns

Mixing compost with topsoil creates a healthy lawn while minimising weed growth. Purchasing topsoil for a new lawn is an effective way to introduce essential nutrients to the soil. Therefore, use a ratio of 1 part compost to 4 parts topsoil to improve drainage and nutrient content. Aim for a depth of 4 to 6 inches, then level the mixture and water thoroughly after sowing grass seed or laying sod.

Can You Just Put Compost on Top of Topsoil?

While you can put compost on top of topsoil, this method is not the most effective way to improve soil quality. Layering compost without mixing may limit its benefits, as it won’t adequately integrate with the soil below. For optimal results, it’s best to mix compost into the topsoil, creating a uniform blend that enhances nutrient availability, soil structure and water holding capacity.

What is the Difference Between Topsoil and Compost?

Topsoil and compost serve different purposes but complement each other well. Topsoil is the uppermost layer, rich in minerals and organic matter, providing a stable foundation for plant roots. Compost, on the other hand, is nutrient-rich organic matter created from decomposed materials. In summary, premium topsoil supports plants and the planting process, while compost enriches the soil with essential components. Using both together can significantly enhance gardening success and microbial activity.

Discover the Secret to a Healthier Garden

Mixing topsoil with compost improves plant health and soil quality. At Alsoils, we provide high-quality products and expert advice tailored to your gardening needs. Contact us today for all your soil and gardening solutions!


Helpful links and resources

Not sure how much you’ll need? Why not check out our topsoil and compost calculators below:

About the Author

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Alsoils

The Alsoils Team

For more than three decades, Alsoils has been a trusted name in delivering superior soil, compost products and offering landscaping services. Based in Hampshire, Alsoils caters to a diverse clientele, including both homeowners and businesses. Our team are experts in all things gardening, so you can be sure you get the very best advice for topsoil, compost, manure and so much more!

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Based on 14 reviews
Mark Belshaw
Mark Belshaw
2023-02-17
Ordered 2 bulk bags of manure on Wednesday, late afternoon and all was delivered by Friday lunch time. Great quality product and excellent delivery turnaround.
Charles Smith
Charles Smith
2022-06-30
Excellent, from order to delivery. 10 tonnes of loose load top soil delivered within a few days. Best price and the 10mm screened soil is great quality. Thank you
Lesley Barry
Lesley Barry
2022-05-15
Excellent product ordered 4 bags of top soil the driver was so accommodating as we have a very long driveway. The customer sevice was excellent. Thank you.
David Robberts
David Robberts
2021-05-13
Excellent product at a sensible price from a local supplier. Staff are friendly and willing to help: I asked if just one bag of topsoil could be delivered quickly and it arrived next day! Great service.
Mark Hibberd
Mark Hibberd
2018-06-11
Smooth execution of the transaction and delivery. Very helpful phone call and conversation. Ordered three bags of Border Blend topsoil. Paid by Paypal. They delivered, on the specified date, carefully, exactly where I wanted the bags placed. All in all, a very pleasing purchase. The topsoil was excellent and had been very carefully prepared. No lumps. Would definitely recommend and I will use again. Everyone I spoke to was nice and helpful.
David Stamp
David Stamp
2015-09-18
Ordered topsoil on Tuesday came by Friday at the exact time quoted. Was WAY cheaper than anywhere else (by about £15 per bag) and was dropped off via a crane on back of the lorry, not by pallet which most of the other places use. Soil was fine and dry. Brilliant !