Amending Your Garden Soil, Organically and Sustainably

Amending Your Garden Soil, Organically and Sustainably

Feed the Soil, Not the Plants

When asked how to grow good vegetables, many gardeners and farmers will say “it starts with good soil.”  Soil is the foundation of your garden, it’s what feeds & aerates your plants.  Good soil is not just dirt, it is is a microcosm filled with microorganisms (hundreds of millions per gram!) that transform organic matter into food your plants can digest. Only with good soil will your plants thrive.

Soil Testing

The first thing you should do before planting a new garden is to test the soil to find out what nutrients it currently holds.  You should probably test the soil of your garden every few years, just to make sure your plants are getting everything they need.  You can buy a simple soil tester at any good nursery and most hardware stores, or you can buy one online.  These will not test everything a plant needs, they will only test the basics:  Ph balance, Nitrogen, Phosphorous, and Potassium.  But that should be a good indication whether or not your soil is healthy overall.

If you suspect there may be lead or other hazardous elements in your soil (for instance, if your garden resides where there was once a house that could have leached lead paint, or near a freeway or gas station), you should have your soil professionally tested by a lab.  This is more expensive, but worth your family’s safety.



Amending Your Soil With Nutrients

Make Your Own Compost

By composting you are recreating nature’s processes of recycling and renewing.  We’ll go into more detail about composting at a later time, but I want to mention this:  if you are afraid of composting or “don’t have time” to compost, just create a pile in the backyard.  Make sure it’s somewhat layered, so it’s not a big chunk of grass clippings.  But really, just make a pile.  Put food scraps, leaves, retired plants, grass, etc. into the pile, and if you don’t have time to turn it that’s ok – let it be.  It will decompose and become compost. (You can also learn about composting and compost tumbler here and here)

Bring In Compost and/or Manure

If you’re just starting your garden, your garden is rather large, or you just haven’t got around to composting, you may have to bring in compost.  We bring in a compost and aged manure mix, to get a more or less good mixture of nitrogen and carbon.  Make sure to use aged manure – it is high in nitrogen, so it will burn your plants if it is new.

If you have a truck – or have a friend or relative with a truck – the easiest and cheapest way is to find your local municipal compost service, and pick up a truck load of compost.  My mother and I picked up a truck load (1 cubic yard) for $20 over the weekend.  I have no idea how many bags of compost that equated to, but um… it was a lot.

If you don’t have a truck, you can usually have it delivered.  Generally there is a minimum delivery, so you may want to go in on it with your neighbors.

To find out how many cubic yards of compost you need to order, use this calculation (it’s fairly standardized):

(length in feet) x (width in feet) x (depth in feet) = (total feet)

then, (total feet) divided by 27 = (cubic yards needed)

Once you have your compost, you’ll want to make sure to incorporate it into your topsoil (the top foot of your soil) with a shovel, fork, cultivator, or broadfork.  If you already have plants planted, you can do this gently, or simply sprinkle around the outside of the plants, carefully avoiding the very base of the plant.  Make sure you do this when the soil is moist but not wet.

Other Deficiencies

If your plants are not looking happy (yellow leaves, stunted growth, purple veins, or sickly in general) and you know it isn’t due to water, sun, nor compost, you may have a deficiency in other areas.  You can send a soil sample to a lab to find out exactly what is wrong, or you can talk with your neighbors and local master gardeners to see if there are particular known deficiencies in your area.

Calcium and magnesium: Unfortunately, in the Pacific Northwest we’re particularly vulnerable to these deficiencies for a number of reasons. If your garden is deficient in calcium and magnesium, you can mix 1 part “agricultural lime” (calcium carbonate) with 1 part dolomite lime (calcium carbonate and magnesium carbonate) – at a rate of 5 lbs. per 100 square feet.  For calcium alone, you can add crushed egg shells to compost.

Phosphorous: Add phosphate rock, 9 lbs per 100 square feet.

Potassium: Add wood ash, 1.5 lbs per 100 square feet. (Note that wood ash has an alkaline effect on soil, so make sure you know your pH first.)



Amending Your Soil With Worms and Microbes

Most healthy soil should have loads of beneficial microbes, worms, bacteria, beetles, mites, and fungi.  Together these things break down organic matter and turn it into plant nutrients, aerate the soil, fend off diseases, and often work with the plants in a symbiotic feeding and fending-off relationship.

However, when you spray chemicals on your soil to kill the bad bacteria, or if you till repeatedly, it kills the beneficial creatures that live in the soil.  Because you don’t have microbes to help the plants break down nutrients and fend off disease, you have to feed the plants more, and spray them more for disease.  This creates a vicious cycle of farming that depletes the earth and relies on chemicals made from and/or distributed by fossil fuels.

If you are reclaiming soil that has not been gardened for some time (if at all), or it has been gardened with chemicals in the past, chances are that your soil is not very “alive” with worms and microbes. Fortunately you can help your soil ecosystem rebuild.

Adding & Encouraging Worms

Worms like organic matter.  Generally, there are two types in garden soil:  red worms – which are often used for composting and live near the top of the soil, and earthworms – which live lower in the soil.  You can encourage red worms by mulching and generally disturbing the soil as little as possible.  (I mulch with straw, which you can find for $5-10/bale at a local feed store – one bale goes a long way.)  And you can encourage earthworms by amending your soil with compost and minimizing tilling as much as possible.


Or if your soil is truly depleted and you’re not finding any worms, you can add them to your garden. There are many kinds of worms, and they all do different things, and people grow them for different reasons.  (Yes, there are worm farms all over the world!)  If you can’t find them locally, several places sell worms online, mostly for fishing bait.  I found the largest selection of worms at the Worm Man’s Worm Farm.  (Watch out for the “Superworms” – yikes).  And they have the perfect selection for the gardener:  a mix of red worms and earthworms called “Lawn and Garden Worms”.  You can buy them in 5 lbs or 25 lbs bags. They recommend 5 lbs per 600 square feet.

Adding & Encouraging Microbes

The best way to do this is to make your own compost.  If you live in a small space, you can create compost in your kitchen, with a worm bin.  A worm bin has the added benefit of multiplying worms, providing extras that you can give to friends or set free in your garden.  If you have room outside, you should create a compost pile or two.  Composting is the subject of another post – as there are loads of ways to do it – but do look into it now if you’re starting your garden!

Compost will help a lot, but to really jump start your soil into recovery, you an add microbes and worms to the soil.  I sprinkle a bit of “Beneficial Bacteria” whenever I’m planting seeds in a new bed.  It’s made by “Down to Earth”, and you can find it at many good nurseries, or online at Bountiful Gardens.

Using Inoculant

Inoculant is rhizobium, a type of soil bacteria.  Legumes (beans, peas, etc) and rhizobium bacteria live in a symbiotic relationship which allows legumes to fix nitrogen (ie, add nitrogen back into the soil – a great thing for gardeners!).  Because each legume needs a different kind of inoculant, most soils don’t have the particular rhizobium necessary to make your beans thrive.  So you have to buy it – it’s available at most good seed shops.  Make sure to get the right inoculant for whatever you’re planting.

From what I’ve learned, there are two good ways to inoculate:  either the “slur” method, or the “stir” method:

  • To slurry: Lay out the seeds in the shade.  Spray the seed with non-chlorinated, clean, cool water.  Shake the inoculant onto the seeds and make sure they are thoroughly coated.  Plant immediately.  Then water immediately.  (Apparently you can also dampen them with a mixture of 1 quart milk to 2 T molasses.)
  • To stir: Mix the inoculant in a small amount of water (approximately 1:1).  Put the seeds in the mixture and coat them thoroughly.  Plant immediately.  Then water immediately.  (This is the method I used.)

Note:  because inoculant is alive, make sure you check the expiration date, and keep it cool and out of sunlight.  You can store inoculated seed for a few hours, but it’s best to plant it immediately.  And according to “Peaceful Valley Farm & Garden Supply”, “you cannot use too much inoculant; but you can use too little.”



To Till Or Not To Till

Gardeners get into heated debates about this issue.  My common sense says that if you are slicing through the soil with big round knives, and at the same time crushing it with a big heavy machine… you’re going to kill microbes and worms.  So if you don’t have to till, you probably shouldn’t.

There are definitely cases to till, however.  When we first moved to our 1/2 acre in Geyserville, the land was dead, depleted, compacted, dirt.  We tried to just dig enough to be able to plant a few starts, and it was too hard to dig – despite watering for a long time to try to break it up.  But since it was dead, probably weren’t very many microbes in there to kill.  And after we tilled the first time, we never had to till again because we had worms and microbes doing the work for us.

The main reasons not to till are that every time you till, you kill worms (they don’t grow back into two worms – it’s a myth), you uproot good bacteria from their homes, and you unearth good nutrients so that they have a greater chance of blowing or washing away.  If you want to see the extreme examples of what can happen when over-tilling, check out the short film “The Plough that Broke the Plains,” the Farm Commission photos from the 30s, or Steinbeck’s “The Grapes of Wrath.”

By enriching your soil and gardening organically and sustainably, not only will your vegetables and fruits be more flavorful – and your family healthier – but your soil will actually absorb 30% more harmful carbon than conventional agriculture.

And Lastly

Whole books have been written on this subject, so I don’t mean for this to be a be-all, end-all resource, but simply a way for you to get started.  A way to let some fears fall away, if you are fearful.  A way to push you to do a bit more, if you have been wondering what to do next.  I encourage you to try new things and have fun with it!