What's the purpose of mixing native soil with store bought soil?

Question

On most store-bought soil, it gives instructions to mix the soil with equal parts of your native soil. Why should I create a mixture instead of using the store-bought soil purely?

I usually buy Kellogg garden soil. The texture is quite coarse - like that of ground up wood chips. I have been mixing this garden soil with store-bought soil conditioner/amendments, but never with my native soil. My native soil is tough clay, so I was hesitant of mixing it in. Could this be the reason why I'm having such bad luck in my first year of gardening? My blackberry and strawberries shriveled after one week of planting. However, others such as raspberry and goji berry are thriving.

Answer 1

Even though it's called Kellogg "garden soil", it does not appear to actually be a soil; it looks more like a soil amendment based on that video, product information and customer reviews.

A soil contains organic matter, nutrients, air, water, minerals, microorganisms, rocks and sediments like sand, silt and clay. Kellogg garden soil is a bag of compost and organic fertilizers intended to be mixed into your existing soil to increase its organic matter and nutrient content.

Based on reviews and customer photos I've seen, it doesn't appear to be a very good product. The compost is not composted fully or screened like it appears to be in the video but as you, and others, have described consists of a lot of uncomposted materials like wood chips. If you can find a good source of compost it will be cheaper. That's the bulk of what's (supposed to be) in the bag. Then add some organic fertilizers and you get the same thing except for less money. A lot less money if you're buying compost in bulk as opposed to bags.

It's a convenience product that has its place but it doesn't appear to be of very good quality.

Answer 2

I watched the video too - this product is intended for mixing with your garden soil at planting time, when you are planting out in the ground. It's meant to improve soil structure, assist with drainage, yet retain moisture, and also contains a small amount of feed.

There's an implication in your question that that's not how you've been using it - have you been using it for potting and not in the ground?

UPDATED ANSWER:

This Kellog stuff isn't causing a problem in your garden - I think what it means when it says 'mix' with your own soil is, it's just telling you, at planting time, when you've dug your hole, to mix the kellog stuff into the backfill soil you've just removed, and which you're going to replace around the rootball when its in position. In other words, don't just surround the rootball with the kellog stuff, but a mix of that and your own soil. That's certainly what I do with any soil amendment at planting time if its not already been dug in all over - that might be my own garden compost from the heap, or peat, or a little of something I've bought at the garden centre, such as soil conditioning compost. Whether it's got 'poop' in it or not, I can't say, but it wouldn't be a problem even if it had, unless you're growing carrots. And yes, it will become part of your own soil - it'll break down over time, creating more humus in the soil, which is a good thing.

If it is mostly wood chips, then the nitrogen already included in the mix will help offset the nitrogen loss once its in the ground.

Answer 3

Not sure. I guess the store bought soil has the function like "soil conditioner".

For example, water retention type soil conditioner can increase the water retention ability; Soil nutrients type conditioner can provide nutrients.

Ref:water retention type soil conditioner