It‘s just about that time of year to start preparing for your garden. But there’s one important step in growing a garden full of fruits and vegetables that some beginning gardeners may not realize: knowing what is in your soil. If this is you, you may wonder why you should do this, what you might need, or how exactly one takes a soil sample. Why should I take a soil sample? Taking a good soil sample can give you an abundance of information that will make your gardening experience an enjoyable and successful one. All plants have certain nutrient requirements. Obtaining a soil sample can show that your soil needs supplementing with nutrients and minerals that aid in the production of a great harvest or the prettiest flowers. Not only will your plants thrive, but they will also live longer. This will, in turn, reduce fertilizer needs, which will save you money.
A soil sample can also show that there could be potentially dangerous chemicals or pollutants that you would want to avoid when growing foods in your garden. Alternatively, it could show that your ground is completely healthy and ready for planting. Nutrients, minerals, chemicals, and pollutants are all things that can affect the growth of plants from the soil. Therefore, it is important to have nutrient-rich ground to grow crops and flowers and other types of plants.
Another important piece of information a soil sample can show are pH levels. This allows you to monitor the acidity or alkalinity of your soil. A soil with a pH number below 7 is acidic, while conversely, a pH level above 7 is alkaline. Most garden plants typically grow best in neutral or slightly acidic soil and will not thrive in soil that is highly acidic or highly alkaline.
Testing your soil may give you an answer on why your garden wouldn’t grow properly in the past or maybe why your grass may grow in patches. It could even show that there is an over-abundance of certain elements in your soil. These are only a few of the many advantages to having your soil tested. No matter the purpose for a soil test, whether it be for a beautiful lawn, a healthy garden, or a large field for crop, it’s always best to know exactly what is in the ground you are working with.
If using a spade, try to avoid disturbing the soil or mixing it up as you remove it from the side of the hole. Additionally, avoid digging too deep as there can be a lack of nutrients below this point; however, if you dig too shallow, there can be too many nutrients. With that being said, for the best sample of your space, 6 inches deep is ideal for a garden. Once you have removed your sample, place the sample into the bucket or container and repeat this process of obtaining samples about 10 times throughout your space at random and add them to your container.
Once you have the core samples all in one container, thoroughly mix them to make one larger sample. This sample should be about 2 cups or 1 pint. You can then transfer your sample to a Ziplock bag or a place it in a container with a lid. Be sure to write the location your samples are from, especially if sampling two or more garden areas, as well as your name and address. You might label these areas back yard, front yard, raised bed, garden area, etc. When you have completed all of the steps, you are ready to submit your samples to your local extension office where they will handle it from there. You will typically receive results in 1-2 weeks.
To understand your soil and your results, you will need to understand soil PH. The PH tells how acidic or how alkaline (basic) your soil is and it tells us whether or not the nutrients are available for the plant to take up. Back in high school when you thought, “I’ll never use this chemistry”, you probably weren’t thinking about how those concepts could help you with your garden, right? When you have the right PH, the plant can take up nutrients that it needs from the soil. In general most garden plants need a PH that ranges from 6.0-7.0. The graph below (pda.org.uk) shows you how much of a nutrient is available at certain levels of PH. The wider the white band the more of that nutrient is available at the level of PH (levels of PH are listed across the top).
Image from pda.org.uk, October 2022. Impact of PH on Nutrient Availability.
(redrawn for PDA from Truog, E. (1946). Soil reaction influence on availability of plant nutrients. Soil Science Society of America Proceedinqs 11, 305-308.).
If you have a PH that is high (8.0), the plant will not be able to take up the iron, manganese, and boron that it needs to thrive. In contrast, if the PH is to low (5.0) the plant will not be able to take up the phosphorus and calcium that it needs. The goal is to have a balance of nutrients so that you can have the best plants and harvest possible. The PH plays an important role in balancing out the nutrients for your plant’s needs. It really is important to know your plant’s recommended PH. Plants such as blueberries, rhododendrons, azaleas, and conifers prefer a more acidic soil (5.0-5.5). Vegetables and ornamentals grow best in slightly acidic soils (6.0-7.0). Note: there are also meters and PH kits available that also help you monitor your soil PH. Now that you understand soil PH, let’s look at a report from a soil sample we took on the farm. Below, you will see an example of results from a soil sample taken from a field where we planted corn.
You can see that the results were very easy to read. The bar graph shows exactly what is lacking in nutrients in the soil, what is adequate and what is high. Knowing this information allows us to make informed decisions about what fertilizer and amendments to use as we prepare the soil for the season. It also shows the soil PH. Again, majority of plants like a PH between 6.5-7.0 and different plants can have a different recommended PH. In our garden plot, we have mixed species of plants, as you probably will also. In general we go with a corn nutrient recommendation when planning fertilizer and nutrients for our garden because fertility for corn is generally adequate for most other plants. Notice the two gray bars show sodium and organic matter. It is a good thing to have adequate organic matter in your soil. If this is low, adding compost can help. Sodium generally needs to be lower. If yours is high, pay attention to your fertilizer and make sure that it is not high in sodium. The great thing about soil samples is that they also give recommendations. Notice the comment section and the graph right above it tells us what we need to do to get the soil right where it needs to be so that we can grow our best crop.
Be sure when you take your soil sample into the lab or extension office, that you specify that area your area growing in and the general size of the area so that the recommendations fit your space and are not based on acres. Follow recommended label rates for any amendments you add to the soil. If your results are in acres, you will need to adjust accordingly to the size of your plot or raised bed. Either way the graph will tell you what you need to look for in amendments and fertilizer options. You will be amazed at the difference in your harvest and plants if you use this basic test to help you make informed decisions about your garden.
Have lingering questions about taking a soil sample? Visit any of our social media pages, message us or come see us in person at The Bloomery to ask any questions! We are more than happy to help!