Putting it in the bag: the new garden soil heads to the soil test lab.
It’s still the first week of starting a brand new food garden from scratch. And as long as your dirt isn’t frozen solid, November is the time to do it here in upper New England. A few days ago I dug a new 5 foot by 20 foot garden space in my lawn by carefully removing the layer of sod. And today I’ve got to send a soil sample out to a lab. You never really know what you are going to find under your lawn, but it’s probably going to be somewhere between rich, black loamy topsoil that’s 5 feet deep and a hazardous waste horror story like Love Canal.
As luck would have it, my soil is closer to loam than Love Canal. It’s about a foot deep. It’s dark.
When I squeeze a handful it crumbles but doesn’t run out between my fingers like sand. It’s got a few resident earthworms in every shovel-full. But it’s the stuff that I can’t see that will determine what kind of work I need to do to help the soil get ready to grow me a good garden here next spring. I could neglect the soil test, take my chances, and maybe grow a good garden… or discover, too late, that my dirt isn’t good for much beyond service as a burial ground for seeds.
Here’s the simple list of what the stuff is that I need to test for: Soil acidity, i.e. “pH” (the acidity of the soil affects just about every aspect of plant growth); Cation Exchange Capacity or CEC (a measure of how well the soil can supply nutrients to the plants); Nitrogen (plants must have nitrogen to grow); Phosphorus (a key to photosynthesis); Potassium (helps plants make the best use of nitrogen and water); Calcium (sort of the Wonder Bread of the soil–helps plants build strong bodies in a dozen ways); Magnesium (an essential ingredient in chlorophyl); Micronutrients (plant don’t need much, but they must have a tiny amount of each: iron, manganese, magnesium, copper and boron).
So with a new garden, and not much time, and no home soil test kits tucked away in my garage/potting shed, I am going to gather a soil sample and send it off to a soil testing lab. I’ve heard stories about people who have heard stories about farmers who can taste their dirt and know what it needs. My palate ain’t that evolved. I suppose I could tell a vinegar-sour acid soil from a sweet soil if it had a pH of 2 (that’s VERY acidic) but to discern the bouquet of a 6.0 pH soil (very mildly acidic) from 7.0 pH (neutral) is out of the question. So dig we must.
Your state university probably has a soil testing lab. You can ask experienced farmer or gardener friends of yours where they send their soil for testing, or you can call you local agricultural extension service. I would steer you away from doing what I did last year…sending your little baggy of soil to International Ag Labs, the Mecca of the “nutrient density” growers. It cost me $50, and took me way, way further down the specialty growers’ rabbit hole than I was prepared for. Not that nutrient density isn’t a very, very interesting niche in the quest for higher productivity organic food, but…trust me…you really don’t need to know about the arcana of nutrient density growing in order to grow a great potato, turnip or head of cabbage.
I’m sending my soil test to the University of Massachusetts Soil and Plant Tissue Tesing Lab. The test costs $13, and our friend and expert gardener Lou Schuller sends her dirt there.
A little bit of science goes a long way: take soil samples from a dozen random positions in your garden. Note: avoid sampling aberrations like where the horse manure just landed.
Instructions for the way to gather your soil sample are on line, but sampling for any soil lab is the same. You want to stake out about a dozen random points in the garden…avoiding any point that might be extreme or out of line. For example, the place where the neighbor’s horse just deposited a steaming garden gift. Put that in your compost pile, but avoid pulling a soil sample from beneath it. In my new garden I grabbed a dozen little stakes and pushed them into the dirt in a rough zig-zag pattern.
Next, find a card board box or a very clean bucket. Wash your trowel thoroughly. Put on a pair of new gloves (old gloves will be coated with who-knows-what that could throw the sample off), or simply wash your hands. This is science now, so pay attention.
Go to each place where you’ve set a stake, scrape off the first inch or so of dirt, dig a couple of trowel scoops out of a hole around 6-8 inches deep, and then take one more trowel scoop down off the side of the hole and throw it in your box or bucket. Now, mix your little pile of testing dirt thoroughly so that you’ve got a homogenous sample of your garden dirt. Let it dry for a day, then mix it again very, very thoroughly and put about a cup and a half in a plastic sealable bag, fill out the test lab’s form, write the check, and send it off. We’ll get the results next week.
Oh! and don’t worry about what we’ll do with the results for a few months. We’ve got all winter to think about soil health. Meanwhile, back in the new garden it’s Week #2 coming up, and we’ll make a big compost pile and tuck the garden, its soil, its worms and its microbial and fungal populations in for the winter.