Soil Amendments

A common problem here on the Palouse is our soil. Sometimes "soil" is too kind of a term - it's more like heavy clay. I once had to use a pick axe to cut away the soil to create a new retaining wall. You can use great websites like the USDA Soil Maps to find out exactly what kind of soil you are working with, but most of us have some type of silt loam. I spent a semester in college studying soil (they really hate it when you call it "dirt"). We looked at composition, drainage, maximum slopes, etc., but pretty much anyone with a yard here can tell you that we're not working with the best stuff on earth. The soil maps say that our Palouse silt loams are "well drained", but I've seen trees drown and suffocate in holes that essentially served as concrete pots in the ground with zero drainage.

So, what do you do? You have to work with what you've got. Some people try to truck in topsoil, but that doesn't work because it's usually just what local construction companies have dug out for foundations and if you live in a newly constructed house it could be the same exact stuff you're already dealing with! So unless you actually need to increase the volume of soil on your property, topsoil is out. The best option is amending the soil that you have in order to improve drainage and increase nutrients. Over large areas, this can become expensive. Here are some general tips:

: : If you can take care of large areas all at once, mix in about a 5 gallon bucket of sand and four 5 gallon buckets of compost (like EKO compost or any other compost that you can buy by the cubic yard at a garden center) for every 25 square feet. Some places even have something like a 3-way mix of mulch, compost, and sand which also works well.

: : If you have an already established yard and can only amend in each new planting hole as you go, then mix in about an inch of sand into the bottom of the hole and use a 2:1 mixture of original soil to compost as back fill (soil that you put back in the hole around the root ball).

: : If you just want to amend your planting beds and aren't planning to plant anything new, spread an inch or two of compost on top of the soil and work it in as much as possible without tearing up any roots.

: : The best top dressing for your planting beds is mulching bark. It doesn't stay in place like river rock and you have to replace it every year or two, but as far as quality of your soil goes it's the best thing. As it breaks down it adds nutrients to your soil and improves drainage. This obviously won't work if you put a weed barrier (the black plastic/fabric type stuff) between your bark and soil, so if you can resist, don't do that. If you make your bark layer two or more inches thick, that should work in two ways to prevent weeds: it will keep sunlight from reaching the soil where the weeds will usually grow and whatever weeds do happen to pop up in the bark are very easy to pull because their roots are just in the loose bark (as long as you don't wait till they're a foot tall!).

mulching bark

: : And last but not least, my very favorite soil amendment is Whitney Farms Soil Conditioner. It is my favorite because a few years ago I set up two planting beds, one with Whitney Farms Soil Conditioner to amend the soil and another with a basic planting compost. I planted gladiolus bulbs in both beds and after two months the bed with the Soil Conditioner produced much taller, fuller blooms than the other. Because of the cost, this is probably the sort of thing that you would want to mix in to each individual planting hole, again at a 2:1 ratio of native soil to conditioner.