| Especially for the capital journal
One of the most common questions gardeners have is how to fertilize certain plants. Many plants have individual nutrient needs, but it is difficult for all plants to guess what you need without knowing what you have. Although soil testing is generally done to find out which nutrients are deficient, it is just as important to know if enough is already there.
The most basic soil test that K-State offers checks the pH of the soil as well as the phosphorus and potassium levels. Most lawn and garden soil tests that come from our soil test lab show more than adequate levels of phosphorus and potassium. If these nutrients are not needed, using them would be a waste of money and can become a source of pollution. In extreme cases, excess phosphorus can affect the absorption of micronutrients into your plant.
Start with a representative sample in different places in the garden or on the lawn. Each sample tested should consist of at least five subsamples. When testing your lawn soil, the samples should be 3 to 4 inches deep. For vegetables, flowers, and small fruits, dig to a depth of 5 to 6 inches. Tree and shrub soil samples should be 10-12 inches deep. Mix the subsamples in a clean container and select from these two cups of soil sufficient to fill a sandwich bag.
A separate sample should be taken if the areas being examined are far apart or if they have been treated differently. For example, if you want to test the soil around your house, the front flowerbed should be one sample, the back flowerbed different, and each side of the house should be separated for a total of four separate samples and tests. If you have two garden beds up front and one has been modified with organic matter and the other has not, you should split those into two tests.
Then take the soil to the Shawnee County Research and Extension Office. Samples are sent to the K-State soil testing laboratory for a fee. Depending on the chosen package, the individual test prices are between 10 and 18 US dollars. Soil tests take two to three weeks to complete, although this time can be longer in high season, generally spring and fall.
Soil samples should not be taken or taken while the soil is moist. If your soil is wet, it is best to wait for the sample to be taken or allow the sample to air dry before submitting it for testing. Do not use artificial desiccants, such as an oven or microwave, as such treatment can result in inaccurate nutritional information. Also, use a clean container to collect the sample. Wet samples are more likely to absorb foreign matter attached to the container, which can also affect soil test results.
Soil tests are useful for identifying nutrient deficiencies as well as soil pH, but they don’t tell the full story. We often hear from gardeners who have difficulty growing plants even though their soil test shows no flaws. Before testing your floors, consider the following common gardening problems.
Not enough sun: Plants need a certain minimum amount of sun before they can grow well. Typically, flowering (and fertile) plants need at least six to eight hours of full sun a day. There are of course exceptions like impatiens, which bloom well in the shade. Move sun-loving plants to more sun or use plants that are better adapted to shady conditions.
Bad physical properties of the soil: Roots need just as much oxygen as water. A dense clay soil or excessive water can limit the oxygen levels in the soil and make it difficult for roots to penetrate the soil. Increasing the organic matter content in clay soils can help rebuild a good structure. For these floors, add and order a 2-inch layer of organic matter.
Walnut trees: Walnuts give off a natural herbicide that disrupts the growth of some plants, such as tomatoes. Vegetable gardens should be at least 50 feet from walnut trees if possible.
Tree roots: Trees not only compete with other plants for sun, but also for water and nutrients. Additional water and nutrients may be required when growing plants near an established tree.
Flat floors: When new homes are built, the topsoil is often peeled off before the floors are brought to grade. Although the topsoil should be replaced, sometimes it is not replaced or not replaced to the same depth as it was originally. They have a subsoil in which plants usually cannot grow well due to poor soil structure. Adding topsoil to a depth of 8 to 12 inches would be best, but this is often not practical. In such cases, try to restore the structure by adding organic matter and working it into the soil.
Too much phosphorus: Most soils in Kansas are naturally low in phosphorus. However, soils that have been fertilized for a number of years can be quite high in phosphorus. Extremely high levels of phosphorus can affect the absorption of some micronutrients such as iron, manganese, and zinc. Soils with a high phosphorus content should only be fertilized with fertilizers that contain relatively small amounts or no amounts of phosphorus.
Improper watering: Roots develop where the conditions are best for growth. Shallow, frequent watering will cause roots to develop mainly near the surface of the soil where the soil is moist. It is better to water less frequently and at greater depth to encourage a deeper root system that is less sensitive to heat and water stress.
Overwatering: Roots have to breathe. In other words, they must have oxygen to survive. Be careful not to water so hard that the soil remains saturated. Water deeply, but allow the soil to dry a little between waterings.
For more information about soil testing in Shawnee County, including prices and soil test forms, visit www.shawnee.k-state.edu/lawn-garden/soil-testing.htm.
Ariel Whitely-Noll is the horticultural agent for Shawnee County Research and Extension. She can be reached at arielw@ksu.edu.
