Gardening Basics: How to Amend Soil

We’ve talked about why composty soil, good watering habits, and a thick layer of mulch are important if you want to garden more organically; it’s all about giving your plants a foundation of good health so that pest problems will be few and far between.

Today we’ll talk about how to know whether you need to add compost to your soil, how much to add, and how to mix it in:

Rich soil makes for happy plants

Most people have some idea of whether their soil leans towards sand, clay or loam. You can find out what soil type you have here, but for our purposes, it really isn’t important.

The main thing to know is that adding compost will help any kind of soil.

Got clay? Compost will help the tiny clay particles bind together in larger crumbs that allow for better drainage and less of that sticky clumping. Got sand? Compost will help it hold moisture. If you’re lucky enough to have that in-between loam, then compost will do a bit of both and help your plants stay happy and balanced in their soil home.

In a new garden bed, I usually add 3-6” of compost to the entire surface of the garden bed and mix it in well to a depth of 6-8” – that is, go down about 6-8” into your existing soil. Mix it up until it’s well blended, so you don’t have large areas that are only compost or only soil.

In an existing garden bed, I’ll often just add an inch or two if it looks like it needs help, mixing it in just a couple inches down. The earthworms will continue your amending work for you! (If you have mulch on the bed currently, I just gently move the mulch aside and amend, then gently rake the mulch back into place. It only takes a few minutes.)

I like to use a spading fork to mix compost with existing soil, or my hori-hori in tight corners where I want to be careful of plants’ roots. Shovels are fine, but they are meant more for scooping soil than mixing it, so you have to work extra hard to end up with an even blend of compost and soil.

If you’re not sure if you have added enough or if your soil even needs compost, try this test:

Run your fingers through the soil and imagine being a plant and trying to send little baby roots out into it. Is it cool, does it both drain well and hold moisture, and is it crumbly and rich? Can you dig in it with your hands and not need a tool? If not, try adding a bit more compost and see how it improves things.

Now a quick what not to do: Don’t add compost to the hole when you plant. It can cause a situation where the plants’ roots circle around in the cushy compost and never venture outside of the planting hole into the great world beyond. A surface tension barrier can also keep water from draining out of your composty planting hole in winter, causing your new plant to drown.

Instead, apply the compost in an even layer to the entire surface of your garden bed, so your plants are invited to spread their roots.

You can use a bagged compost amendment or buy it in bulk from many landscape suppliers if you have a truck, or you can make your own from garden clippings and non-noxious weeds. (Check out some excellent real-life examples here.) Manure works great as an amendment as well, so long as it’s been composted long enough that it looks and smells more like soil than anything else!

Don’t use potting soil in place of compost since it contains sand (not helpful), and if you do buy bagged compost, try to find one that contains more than just composted wood (it should say on the bag).

Once you’ve enriched your soil with compost, the next step is to add some mulch! We’ll talk about that tomorrow.

What’s worked for you? Do you have any tips for improving soil? Let me know in the comments below!


10 responses to “Gardening Basics: How to Amend Soil”

  1. I can never create/purchase enough compost for my many beds, but I’ve found that simply planting beds improves the soil–it attracts micro&macro organisms and the soil does loosen over time. When starting off, it helps getting plants from friends that have proven themselves to handle the conditions of one’s local climate. My soil is crumbly now but you wouldn’t believe what I planted in harder clay soil, which has taken off over the years. So, yes, amend when possible, but just plant when not! 🙂

    Monica’s last blog post..Mish-Mash Monday

  2. I like the advice to run your fingers through the soil and imagine you’re a root looking for a place to grow. I was transplanting some annual vines from a container into one of my beds today and I was doing just that. It really does make a difference to think ‘can those tiny roots grow in this soil or do I have to loosen it some more’.

    Debbie R’s last blog post..Deer-Resistant* Annuals

  3. Monica, as always – fantastic advice. You are absolutely right! The roots really break up soil and keep the sun and rain from pounding on the soil surface, and great point about the micro-organisms flourishing near plants.

    Debbie, doesn’t it make a world of difference to imagine the roots actually trying to take hold? I’m glad to hear you do it too!

    Genevieve’s last blog post..Organic Gardening 101: How to Amend Soil

  4. Thanks fr adding the link to my compost entry. The last thing I tried on the bottom of my bin (layers of newspaper, a layer of fabric weed barrier, and the fine-gauge chicken wire) worked. A few small feeder roots still worked their way in, but the roots were easy to detangle from the compost; it was NOT one huge root-bound mess. Turning a lot also helps. AND I found a great compost activator/speeder upper: barley left over from beer-making and the juice leftover from fermenting. 🙂

    Monica’s last blog post..Mish-Mash Monday

  5. Making a new garden bed. Conditioning a garden bed is an ongoing effort. Here is my method. Building a New Garden Bed.

    General overview of preparing a garden bed which is basically grass covered to begin. The various operations are simplified with the right tools. Most can be rented at a reasonable cost, if the size of the garden doesn’t warrant purchasing.

    I have access to softwood chips and vegetative compost, plus what I make from spent vegetation, which I utilize liberally. The chips break down in about a year, and a layer of compost and chips is applied each year. All my vegetables are larger than life. The chips are utilized also for top mulch after the vegetables are well established to maintain moisture, particularly from evaporation.
    .-= Durgan´s last blog ..Cold Room in Baseme3nt =-.

  6. […] Take care of your soil, water regularly, and apply mulch. As a rule of thumb, pests find it easiest to attack plants that are already sickly or unhealthy in some way, and I most often see thrips on plants that are in hard, dead soil, with no mulch or regular water, so if that’s your garden, a little preventive work can go a long way towards preventing future pests. […]