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6 Ways to Test Your Garden Soil

To understand what your soil needs to be able to produce the biggest produce and prettiest flowers, you need to understand what your soil is made out of. In this post, I’ll go over six different ways to test your soil to give you a better understanding of what your garden needs.

What Is Soil Made Of?

To understand how to test your soil and what we’re looking for when we test, we need to have a basic understanding of what soil is made out of and how it works.

Soil, fundamentally, is composed of three main components: minerals (tiny rock particles), organic matter (the remains of plants and animals) and living organisms (fungi, bacteria and nematodes).

The texture of the soil – and it’s subsequent health – is driven by the shape of the tiny minerals within it. For example, sandy soil feels gritty due to the large size of the mineral particles. Clay soil feels sticky because it has finer particles which can hold more water.

This diagram by the USDA can help you visualize what makes the different soil types – the percentage of clay to silt to sand will tell you what type of soil you’ve got.

usda soil types

1. Test Your Soil Composition In a Jar

This very low-tech method can help you understand the percentages in your soil of the different soil types: sand, loam and clay.

To perform this test, simply dig into an area of your garden that you’d like to test – clear away the grass and roots and organic material until you’re dealing with just the soil. Scoop a few handfuls into a mason jar until it’s 3/4 of the way full. Fill the rest of the way with water and let sit for at least 24 hours.

If you want to test a larger sample size, you can take samples from around your garden and mix them all together in a bucket to make an average sample, or run separate tests in multiple locations.

Due to the consistency of each that we talked about above, we know that the sand will sink to the bottom first, then the loam, then the clay. Your result after 24 hours will be layers of soil in the bottom of your jar.

2. USDA Online Soil Survey Website

If you’re looking for a more detailed, more tech-y method of testing your soil, you’ll want to check out the USDA Online Soil Survey Website.

Before we bought this property, I knew we wanted to grow hops and other crops. Since I daydream better than I plan, I went to the USDA soil survey website to see what kind of soil our new farm would have.

While not 100% accurate, it’s a great place to start. There’s a bit of a learning curve, but once you get the hang of it it’s really neat. In the first tab you’ll select your Area Of Interest (AOI) and in the second tab, you’ll be able to see the outline and explanation of the different soil types in your AOI.

Here’s an example of part of our property:

You can see it gives you the classification of the soil “sumerduck loam”, the slope “2 to 7 percent slopes” and if it floods or not.

If you click on the blue classification, it gives you even greater detail:

While this fly-out gives you a TON of detail – probably more than you want – the parts I find especially useful/fascinating are the “mean annual precipitation”, “mean annual air temperature”, “frost-free period”, the “typical profile” which tells you want to expect in layers as you dig down.

For example, ours is silt loam from the top to about 11 inches down, clay from 11-49 inches and channery loam from 49-65 inches.

The “natural drainage class” and “runoff class” are especially important if you have a drastic slope. The “capacity of the most limiting layer to transmit water” (ours is .57-1.98 inches/hour), the depth of the water table, and the “available water storage” are particularly important in drier climates.

If you don’t know what a term means – for example I didn’t know what channery loam meant – you can always google the term and learn more.

What’s amazing, is that all of this information is available across almost every inch of the United States, so if you have several properties you’re looking at, or are thinking about starting a new garden plot somewhere you’re not familiar with, this information is available to you – for FREE!

The property we were going to buy before this one was labeled “not prime farmland”, “very high runoff class”, 10-20 inches to a restrictive feature (fragipan), and had a very low available water storage in profile. Thank goodness we didn’t buy it!

3. Soil Quality Report Card

This simple technique is merely a survey you fill out yourself regarding your soil. While this can give you some insight into the current state of your soil, it’s best to fill it out at least once a year (preferably twice a year) over the course of many years to mark your progress.

Going back over several years of report cards will let you know if what you’re doing to improve your soil is actually working, or if you need to change approaches.

Here are a list of example soil quality report cards from various extension agencies across the US. Find the one closest to you or look at many of them and create your own. NRCS Soil Health Card.

4. Soil Density

For fairly cheap you can buy a handful of wire flags from your local hardware store – the kind used to mark power lines or boundaries. Over the area you’re interested in, push a number of these into the ground in a grid-like pattern.

How hard are they to push in? Do they slide right in with firm pressure, or do you have to struggle to push they in before they bend? Is one section of your area of interest harder than another.

I can tell you from personal experience, during a drier week, most of our hop yard is as hard as rock. A landscaping flag will go in barely 3 or 4 inches before bending.

ways to test garden soil

5. Soil Drainage

There are several ways to test this. First is to simply observe your ground after a long, soaking rain. How long does it take for the water to drain? Is it instant? 12 hours? 24?

Additionally, you can dig a hole and fill it rapidly with water. Watch to see how quickly, if at all, it drains.

6. Test Soil Acidity With Vinegar

If your soil’s pH is your concern, there’s a very easy method to test for that. Simply collect about 1 cup of soil (maybe extras from one of the other tests above) and add 1/2 cup of vinegar to it. If it fizzes, you have alkaline soil, with a pH of between 7 and 8.

If nothing happens, add some distilled water to another sample of soil and sprinkle on some baking soda. If it fizzes, you have acidic soil.

If nothing happens in either scenario, you may have perfectly neutral soil.

These six ways are all free (or nearly free), however your local extension office is able to perform detailed tests for a small fee. Simply Google “agriculture extension office [your area]” and give them a call for instructions!

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