Spread a layer of your new topsoil evenly over the existing soil in your garden and then dig or till it into the existing soil that you’ve loosened.
You may decide to use a rototiller for a variety of reasons. If you are adding the topsoil to your garden to increase its fertility, you’ll want it to extend down into the ground so plant roots can access it. Further to this, adding soil on top of a different type soil can create problems; the two soils are likely to have different profiles and structures and therefore different water holding capacities. Water is likely to remain in one of the soils without moving to the other. This can cause drought stress even in well-watered gardens or alternatively drown plants, neither of which is what you want.
Distribute enough soil so the topsoil layer will equal a minimum depth of 6 to 8 inches but anywhere up to 12 inches is ideal. Topsoil depth is very important as too little topsoil means you will see little to no benefit which would be frustrating and disappointing after all your efforts.
When it comes to spreading the soil, it is best to work backwards, again to avoid compaction in the areas you have already laid. Distribute the soil in small piles around the area and use a rake to spread it out evenly and you can then use a fork to mix it into the top layer of the existing soil if necessary.
Be sure to use a dark brown good quality loamy topsoil like ours that’s moist, smells earthy, crumbles in your hands and is free of weed seeds, rocks and debris.