How and Why to Test Your Soil

How and Why to Test Your Soil

Part of Ep. 304 Early Winter Garden Care

Join UW-Extension Soils Specialist Sherry Combs to learn how to test soil and how to compost properly.

Premiere date: Sep 30, 1995

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley:
I'm with UW-Extension Soils Specialist, Sherry Combs and we're standing in the middle of a "W" in her garden. Sherry, why do you have a "W" in your garden?

Sherry:
I intend to plant a new garden in here next year, vegetables. And, I need to test my soil. And, I'm going to be sampling at each point of this "W" today.

Shelley:
Why do we need to test soil?

Sherry:
Well, how would you decide how much fertilizer to apply for this site, for a vegetable garden?

Shelley:
So looking at it isn't going to give me the answers, is it?

Sherry:
No, no, no answers at all. In fact, that's not a very good way.

Shelley:
I have friends that put in lime every year. I mean, is there just not a simple way to do this?

Sherry:
No, there isn't really. The simplest way is to take a test. That's actually the most efficient because then we're able to match exactly what your soil has for nutrient supply with what your crop needs for nutrient supply. And, either tell you not to apply more nutrients and lime, or to instruct you how much and what kind to apply.

Shelley:
So, too much isn't necessarily good.

Sherry:
No, you can get some poor crop growth with too much nutrients. Also, some environmental concerns come up with too much nutrient additions.

Shelley:
Well, I know, like if I over-add nitrogen, I end up with great leaves and very few flowers and fruits.

Sherry:
That's right and that's one example of detrimental crop growth.

Shelley:
OK, you've convinced me. How do I go about doing this? You said sample at every point.

Sherry:
Yeah, we'll use a probe and this is a standard tool for soil scientists. It can be borrowed at the Madison or Marshfield soil testing laboratories or at your local county extension office. And you'll push it into the soil to a depth of about six to eight inches because that's what I'm going to be tilling here next year. So, I'll be mixing this soil up to a depth of six to eight inches.

Shelley:
Isn't it easy to probe if it were already tilled?

Sherry:
Sure, it's easier to probe, but you can't get a very good control of the depth that you take when it's tilled. So, we recommend that you sample prior to tillage.

Shelley:
OK, we dump it in there. Now, we're going to do this at every point of the "W." What if I don't have a probe?

Sherry:
You can easily use a trowel or a shovel. And, we'll show you the trowel. Step it into the soil to a depth of about six to eight inches as we did the probe.

Shelley:
The same depth.

Sherry:
Bring up the wedge and then carve off the corner of the soil. And, place it in the bucket, as well.

Shelley:
Now, do I have to take this whole bucket in to the soil lab?

Sherry:
No, we don't want that much soil to test. We test a small portion of it. So, it's very important that you take a good sample. But, what we want you to do is fill up this bag with about one to two cups of the soil after you've mixed up all of the sub-samples in that bucket.

Shelley:
Stir it up. OK, and what's the blue sheet for then?

Sherry:
Well, this tells us what crop you're going to grow. And, since the recommendations are specific for the type of crop, whether that's vegetables or flowers or fruit crops. We need to have you fill out this blue sheet to give us that information.

Shelley:
OK, then what do we get back from the lab?

Sherry:
You'll get a report back that says, for the sample that you sent in, what the level of pH, organic matter, available phosphorous and available potassium are, if those levels are low or optimum or excessive. And then, how much nutrients and lime that you may need for optimum crop growth.

Shelley:
OK, why are we doing this at the end of the growing season?

Sherry:
Well, I'm going to till next spring, so this is a good time to do it, before tillage. I only have to do it once every three years. So, it gives you a lot of time after you get your report back to think about how you're going to plan your garden, how you're going to apply fertilizer and get ready for spring.

Shelley:
Great, thanks, Sherry. You can find out more about soil tests from your local county extension office.

Here we've got a garden bed all cleaned up and ready to plant next spring, but you have to take all the debris out of the bed and do something with it. I'm with Dane County Extension Ag and Natural Resources Agent, Mindy Habecker. Mindy, we've got a pile of garden debris here and we've gotta do something with it. You are going to show me how to compost it. Tell me what compost is, first. Let's start out with a definition of compost. Well, Shelley, compost is just biologically broken down organic materials that form something similar to a soil. It has a granular texture, a pleasant smell like the earth and it is a perfect soil amendment with a lot of nutrients and a lot of benefits to your soil.

Shelley:
I've heard somebody call it black gold.

Sherry:
That's right.

Shelley:
Alright, what goes into it?

Sherry:
Well, you want a backbone of about two-parts green material or high in nitrogen materials, to one-part brown materials. The green materials can be such things as what's coming out of your last year's garden.

Shelley:
Your vines, your grasses.

Shelley:
Your vines, your broccoli, your annual flowers. All sorts of things that aren't heavily diseased or insect infested. You don't want to put those materials in.

Shelley:
So, grass clippings count.

Sherry:
Right, that's another major green material, your grass clippings. And then, your brown material can be such things as corn stalks, of which anything that's long like vines or corn stalks. You want to snip them so that they're no more than two feet long or you have problems turning your pile with a pitchfork.

Shelley:
So, keep it in small sizes.

Sherry:
Right.

Shelley:
Now, if green is high in nitrogen, then brown is high in ...?

Sherry:
It's high in carbon. And, your leaves fit into that, straw, a little bit of sawdust that would fit in there, too.

Shelley:
Alright, what about kitchen scraps?

Sherry:
Kitchen scraps are a wonderful addition. They fit in with the green materials. So, you want to add such things as your fruit waste, your vegetable waste. But, out of all your kitchen scraps, you don't want to add any fatty foods or any meats into it. But, coffee grinds can go in, egg shells. Your fatty foods or meats will lead to rancid piles, perhaps, and also--

Shelley:
Raccoons, maybe.

Sherry:
That's right, things like raccoons.

Shelley:
Alright, if we don't want to add those things, are there other things we shouldn't be adding to compost?

Sherry:
Well, I touched on one. You don't want to add any noxious weeds. Weeds that, if your pile doesn't heat up enough, that you may have persistent problems in future years. Another thing you don't want to add are any pet waste, such as cat or dog waste of which they can transmit some of the diseases that they have to us. So, you want to keep those things out of your compost pile, too.

Shelley:
OK now, here's a pile that we just started. Is the size appropriate? Does it make a difference?

Sherry:
The size is great. You want to check with your local ordinances, first. They may dictate where your pile can be placed, the size of the pile, whether you need a bin structure and, also, what you can add to your pile. But a pile that's about 4'x4'x4' is great. That will give it enough mass that it will heat up, even in the winter time some, but it isn't too large that oxygen can't penetrate because what breaks down the materials is bacteria which needs oxygen to breath and respire just like we do.

Shelley:
Why do you have a layer of soil on top of your garden debris here?

Sherry:
Well, the soil actually provides you with all the bacteria you need to get a compost pile started. It's ubiquitous in the soil itself and you don't need any special additives such as they sell in a lot of expensive catalogs. You can just add finished compost or soil and it will provide everything you need.

Shelley:
So, that's our starter.

Sherry:
Yeah.

Shelley:
What else?

Sherry:
Well, we want to make sure it's moistened. That bacteria--the pile should be about as wet as a moist sponge so the bacteria have enough moisture to thrive on. And, you can moisten it as you go. If you haven't moistened it until your pile is up to the four feet, then make it somewhat concave at the top. That will collect the moisture throughout the year. As wet as a moist sponge.

Shelley:
You said turn it once in a while and we're done.

Sherry:
That's right, yes. It will compost primarily in the center. Your outside ring won't be composted. So, you want to flip your pile over so that what's on the outside goes in the center and it heats up.

Shelley:
Where it's hotter.

Sherry:
Right, and composts completely.

Shelley:
OK, great. Thanks, Mindy. So, go ahead and compost all season long, whatever the season.

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