Healthy soil is the foundation for any thriving garden. Soil that is rich in organic matter and nutrients provides plants with the essential elements they need to grow strong and produce an abundant harvest. However, not all soils are created equal, and it is essential to understand the makeup of your soil to improve its fertility and support healthy plant growth. Let’s explore how to determine your soil’s pH levels, composition, and nutrient content.
pH
pH testing is a measure of the acidity or alkalinity of your soil. The pH scale ranges from 0 to 14, with 7 being neutral. Most vegetables prefer slightly acidic soil with a pH between 6.0 and 7.0. However, some plants such as blueberries and potatoes thrive in more acidic soil with a pH between 4.5 and 5.5.
Testing your soil’s pH is important because it affects the availability of nutrients for your plants. If your soil is too acidic or alkaline, certain nutrients may not be available to your plants. For example, if your soil is too acidic, your plants may have difficulty absorbing calcium and magnesium, which can lead to stunted growth and poor yields. After testing your pH, see my post on Amending Soil pH Levels.
Composition
Soil makeup analysis involves testing your soil’s texture, structure, and composition.
This is important because it affects how well your soil holds water, drains, and provides nutrients to your plants. Sandy soils drain quickly but do not hold water well, while clay soils hold water well but drain slowly. Knowing your soil’s structure and composition can help you determine if you need to add organic matter or other amendments to improve the soil’s structure and fertility.
Nutrients
Understanding your soil’s nutrient content is essential for maintaining plant health. Plants require three primary nutrients: nitrogen, phosphorus, and potassium. These nutrients are often referred to as NPK and are listed on fertilizer packaging in a three-digit number. For example, a fertilizer labeled 10-10-10 contains equal parts nitrogen, phosphorus, and potassium. Soil testing can also reveal the presence of micronutrients, such as calcium, magnesium, and iron, which are essential for healthy plant growth.
Testing
You can have your soil tested professionally or you can do it at home. Let’s go over how each work.
Lab Testing
Sending a soil sample to your local extension office is a simple and effective way to get a comprehensive analysis of your vegetable garden’s soil. The analysis will provide you with information on your soil’s pH level, nutrient content, and composition, as well as any other soil properties that may be affecting plant growth. Most offices will charge a small fee. Currently in Minnesota, the fee is about $20 per sample. Here’s how you can send a soil sample to your local extension office:
Locate your local extension office: You can do this by searching online or by contacting your local government’s agricultural department. This is my local extension at the University of Minnesota.
Collect the soil sample: Follow the instructions provided by the extension office to collect a soil sample. Typically, you will need to collect soil from several locations within your garden to get an accurate representation of your soil’s properties. Be sure to use clean equipment and avoid any areas where you have recently applied fertilizer or pesticides.
Package and Send: Once you have collected the soil sample, place it in a clean container or plastic bag. Label the container with your name, the location of the soil sample, and the date of collection, and complete any required forms.
At Home Testing
Composition Test
This first test will let you know what your soil is comprised of and how much. Your percentage of sand, silt, and clay. You can use this information to amend your soil with the appropriate additives if necessary.
Fill a glass mason jar 1/3 of the way with a scoop of your soil from one area of your garden, removing any small rocks or debris.
Add one teaspoon of dishwashing detergent and fill the rest of the jar with water leaving an inch of space at the top.
Place the lid on and shake for a few seconds. Let the dirt settle in the jar for 24 hours.
The bottom layer will be your sand, the middle layer is silt, and on top will be the clay.
Biology Simulations has instructions on how to use the soil analysis chart to determine your percentages and classify your soil type.
Nutrient and pH Test
Purchasing an at-home test kit for nutrients and pH is an easy and affordable way to get a good understanding of your soil. You can visit your local garden center or purchase a kit online. Once you have your kit, collect a soil sample from the area you plan to test, making sure to remove any debris or rocks. Most tests use 4 small tubes, one for each nutrient as well as pH. Follow the kit’s instructions, then shake or mix thoroughly. After waiting the recommended amount of time, compare the color of the solution to the chart provided with the kit. This will give you a reading of the pH and nutrient levels in your soil, allowing you to make any necessary adjustments to ensure optimal growing conditions for your plants.
