Garden Prep

2010 Gardening Info Series Topic #3:
"Preparing The Garden For Planting"

The first two topics in our spring Gardening Info Series were, "Why Garden?" and "Selecting a Garden Site". Now that you've decided to garden and have selected a suitable garden site, it's time to evaluate and prepare the soil, and then you'll be ready to plant!

There are three basic steps to follow in preparing a garden for planting.

Step 1: Test the soil

If you will be gardening on new ground, if it's been 2 years or more since your last soil test, or if you have recently not been happy with the quality of produce coming out of your garden, I highly recommend that you test your garden soil.

You'll see soil testing kits at garden stores, or I recommend sending a soil sample to the University of Wisconsin Soil Testing Lab, which offers a $15 soil test for home gardeners that includes analysis of pH, organic matter, phosphorus, and potassium; the report also includes recommendations for how to adjust the soil pH, if necessary, as well as how to select the proper fertilizer for your soil's specific needs. For additional fees, the lab also offers additional tests, including tests for micronutrients, soluble salts, heavy metals, physical analysis (percentage sand, silt, clay, and soil texture), etc.

You can collect your garden soil sample anytime when the ground isn't frozen or overly wet. If you will be growing vegetables, I recommend testing to a depth of 6 inches and taking a minimum of six samples from multiple locations within your garden plot. There are resources available from UW-Extension on how to properly collect a soil sample. You can also get more information from the UW Soil & Plant Analysis Lab's website or call the lab directly at 608-262-4364 if you have additional questions.


Step 2: Amend the soil, if necessary

The soil testing laboratory will make recommendations on whether or not and how to go about improving the fertility and quality of your soil. It is best to follow these recommendations to ensure good yields and quality of the produce you plan to plant this season. Following recommendations specific to your garden site is much better than guessing and randomly adding general purpose fertilizers to your garden. Many people don't know it, but overfertilization of the soil can actually diminish produce quality and vegetable & fruit yields. The bottom line is, when it comes to fertilizers, more is not always better. Also, though they are more expensive, I recommend using organic fertilizers. Organic fertilizers are safer for people & the environment and they are better for plant growth and long-term soil health.

One amendment that should always be on your mind as a gardener is the addition of organic matter!!! Organic matter is a complex topic, but basically, instead of just taking, taking, taking from the soil, as we do when we grow and harvest food year after year from the same ground, we should give back to the soil through the addition of organic matter. This can include adding plant-based compost, crop residues after harvest, green manures, composted animal manure, etc. Your soil test report will indicate whether the soil is in an acceptable range or in a low range for organic matter. But remember, organic matter is constantly being broken down and used up in the soil AND CHEMICAL FERTILIZERS ARE NOT AN ADEQUATE SUBSTITUTE. Therefore, unless you are regularly putting organic matter back into the soil, the soil organic matter value on your test results will inevitably decrease over time, as will the productivity of your garden. We want high levels of organic matter for sustainable gardening, so start making that compost!


Step 3: Prepare a well-aerated seed bed

After you test your garden soil and make the appropriate corrections through amendments for soil health & fertility, it is important that you now create a well-aerated soil environment for your plants to root themselves in.

Healthy soil is composed of many things: minerals, weathered down rocks (sand, silt, or clay), living and dead organic matter, active microorganisms, and last but not least, water and air. These last two ingredients, water and air, are essential to support healthy plant growth as well as to provide the right habitat for beneficial soil organisms that will help your plants grow!

The goal of Step 3 is to create airy soil, as opposed to trying to grow crops in compacted soil. When soil is well-aerated, air, water, plant roots, earthworms and other beneficial organisms will be able to infiltrate through the soil layers properly, and this, in conjunction with your now amended, fertile soil, will lead to strong, healthy plants that will bear much good fruit.

There are many ways to create well-aerated garden soil. You can use a rototiller if you have access to one. There are many types of rototillers out there, and not all are created equally. If you go this route, you should be sure to use a rototiller suitable to your garden conditions.

If you don't have a rototiller that can do the job, consider double digging your plot using a spade and a digging fork. There are many books and websites that detail how to double dig a garden. My experience has been that double digging a garden produces great growing results. HOWEVER, this is a very, very labor intensive process and I only recommend it if you are exceptionally motivated and also have a strong back!!! This year in one of our WFG demonstration gardens, we are testing the efficacy of double digging. For select crops, we will plant half the beds in double dug beds and half the crop in beds that will only have had the soil surface turned over with a shovel. We'll be able to tell you the results of our trial next season!

In the meantime, if you don't have a rototiller and you want to save your back, consider one of two other options: One, just turn the soil over with a shovel right before your plant it. If you have a rake or some other similar tool, use it to break up large chunks created by the shovel. The second method you can use to aerate the soil is to use a special hand tool called a broadfork, such as this one sold by Johnny's Selected Seeds of Winslow, Maine. The broadfork creates air spaces deep down but keeps the overall structure of the soil intact; that means it doesn't break up healthy soil aggregates or disturb the habitat of soil microorganisms. In short, both these methods, the shovel & rake or the broadfork, will loosen things up in your garden and create a well-aerated medium in which to grow your veggies.

One final thing to consider that can affect soil aeration and water infiltration capacity in the garden is the option to build raised beds. Some people like to construct raised beds with wooden sides that hold all the soil in. These types of raised beds contain the soil very nicely and can be attractive as well. Or, if you are like me and don't want to spend a lot of time or money, you can just make yourself some walking paths and use the soil from the walking paths to raise up your growing beds a little. If you have really bad garden soil, you may want to consider purchasing some extra topsoil and/or compost as you create your raised beds.

Keep in mind that growing in raised beds in not necessary for growing good vegetables. However, growing in raised beds THAT YOU NEVER STEP IN!!!! will give your plant roots a nice, deep, aerated growing medium. Plus, your raised beds will drain much faster in spring or during rainstorms throughout the season. Therefore, if you anticipate drainage to be a problem, raised beds are a worthy option.

Whether you use raised beds or just flat beds or rows, please, please please watch where you step in your garden. It may not seem like a few footsteps here or there would make much of a difference, but remember that plant roots, earthworms, and both air and water need spaces to grow and flow properly. If possible, create designated walking paths within the garden and let the plants, bugs, air and water have free reign in the growing spaces.


In summary, the three steps to garden soil preparation are:

1) Soil Testing
2) Soil Amendments
3) Soil Aeration


You are now ready to plant your garden seeds & transplants. Happy Gardening!