For plants to grow properly, they need nitrogen, phosphorus and potassium. These are taken up into the plant through the soil. A soil test determines the level of these nutrients in the soil. If levels are deficient, the needed nutrients can be added.
Soil testing is an important tool. Excess or improperly applied fertilizer can end up in storm sewers and contribute to nutrient pollution in lakes, streams and rivers. Excess phosphorus promotes rapid and abundant algae growth in freshwater. Too much algae disrupts ecosystems, harms wildlife, negatively impacts water recreation and may contain toxins that sicken people and pets. Over-liming or over-fertilizing lawns and gardens can cause problems with plants and contaminate surface water. Testing the soil saves time, money and the environment.
Conducting the test now helps prepare for fall fertilization and lime applications if needed. The soil brought to our office is tested through the University of Kentucky Soil Testing Laboratory at the research station in Princeton.
The soil test determines pH of the soil. The pH indicates the degree of acidity or alkalinity of the soil. It is important because pH affects the availability of nutrients to plants.
The pH scale ranges from 0 to 14. A pH of 7 is neutral. Values below 7 make up the acidic range of the scale, and values above 7 make up the alkaline range. The pH scale is not a linear scale but a logarithmic scale. Soil with a pH of 8.5 is 10 times more alkaline than a soil with a pH of 7.5, and soil with a pH of 4.5 is 10 times more acidic than a soil with a pH of 5.5. Many plants will grow at pH levels of 6.0 to 7.0. Acid-loving plants, such as azaleas and rhododendrons, prefer a pH of 4.5 to 5.0. The pH is used to determine if lime should be applied to increase the pH of the soil.
The label on a bag of fertilizer has three numbers separated by hyphens. The numbers represent the amount of nitrogen, phosphorous and potassium, respectively, contained in the bag on a percentage basis by weight. A bag of 10-10-10 fertilizer contains 10 percent nitrogen, 10 percent phosphorus and 10 percent potassium. A 100-pound bag of a 10-10-10 fertilizer would contain 10 pounds of nitrogen, 10 pounds of phosphorus and 10 pounds of potassium. The remaining 70 pounds is filler used to spread the fertilizer evenly.
Fertilizers with different ratios of nitrogen, phosphorus and potassium are available. Look for the fertilizer ratio that best fits the recommendations of the soil test.
The soil test does not determine the nitrogen level. Plants need nitrogen to grow. The amount of nitrogen applied is determined by the plant or crop.
Phosphorus is essential for seed and fruit formation and root growth. The soil test, as well as the fertilizer bag, refers to phosphorus as P2O5. The University of Kentucky soil test results refer to phosphorus as phosphate.
Potassium, also mentioned as potash, is essential for root development and plant growth. The soil test result and fertilizer bag use K2O when referring to potassium.
The number of soil samples that should be tested from a lawn depends on your yard. If the soil in the front yard is different from the back, then two samples should be tested. Sample problem areas and areas with shrubs or flower beds separate from the lawn.
When collecting a soil sample from the lawn, take a garden trowel and insert it 4 inches into the soil. Remove a trowel full of soil and set it aside on a sheet of newspaper so it will be easy to place back into the hole. Then go to the back of the hole and make a slice of soil about 1 inch thick and 4 inches deep. Place it into a plastic container. Repeat these steps in eight to 10 locations in your yard. Take soil from a number of different locations to obtain a representative sample.
Next, remove the thatch and aboveground parts of the grass from the container. Mix all the soil in your container together and crumble big clods. Place the soil on newspaper to let it air dry for one or two days out of the way where it will not be contaminated by foreign matter. Then take two cups of soil to the County Cooperative Extension Service Office. In Daviess County, the cost of a soil test is $8 per sample. Tests will be completed in seven to 10 days.
To collect a soil sample from the vegetable garden, repeat the steps listed for the lawn, except push the trowel down to a depth of 6 inches. Vegetables have deeper root systems than grass. Collect soil from eight to 10 locations within the garden.
The soil in your lawn and garden should be tested every three to four years. For more information, contact the Daviess County Cooperative Extension Service at 270-685-8480.
As vegetables are finished producing in the garden, destroy or remove the plants to slow down the development of disease and to prevent insects from overwintering in the debris.
Owensboro Regional Farmers' Market is open from 8 a.m. to noon or sellout on Saturdays, and from 7 a.m. to noon on Tuesdays and Thursdays at 1205 Triplett St. Fruits, vegetables, meats, jam, jellies and baked goods are available.