There are many factors that will affect the viability of soil for your plants. Soil may have a loamy and light, clay or sandy consistency. PH levels may affect the type of plants you can grow in an area. Topsoil temperature can affect the rate at which plants grow and whether they will be able to survive. It is especially important to test your soil's temperature before starting your garden in the spring.
Select the area you want to test as a potential place for a garden. Take a measurement of the air temperature by holding your thermometer at shoulder height for one minute. Write your information in your notebook. Make sure to place the date next to your reading.
Record the temperature of the ground surface by laying your thermometer flat on the dirt surface for one minute. Record the information in your notebook.
Measure 2 inches from the bottom of your dowel rod and use your marker to mark the spot on the dowel. Repeat the process for 6 inches and 12 inches.
Press your dowel into the soil until the 2-inch mark is even with the soil surface. Put your thermometer in the hole you made. Wait one minute to record the temperature. The best temperatures for plant growth are between 65 and 70 degrees F. Early season seeded vegetables can be grown when the soil reaches temperatures between 65 and 75 degrees F at a depth of 2 inches in the soil. These plants include arugula, beets, broccoli, peas and cabbage.
Press the dowel into the soil to the 6-inch mark, and then replace it with the thermometer. Wait one minute to get a reading. Plants such as tomatoes, eggplants, peppers and squash do well when soil temperatures are between 65 to 75 degrees F at a depth of at least 4 inches.
Test the soil temperature at a depth of 12 inches by pushing the dowel rod to the 12-inch mark and then replacing it with the thermometer. This will give an indication of how cold or warm the soil is deeper in your garden area.
Repeat the process each day at mid-day for a week to make sure the temperatures are consistent and safe for your plants before planting.