How Often Should You Soil Test a Vegetable Garden?

New Gardens

• Testing the soil before beginning a new garden lets you know whether the soil contains the nutrients your vegetables need to thrive. Although the soil test can be taken any time the soil can be worked, testing it in the fall allows soil amendments, such as limestone or sulfur for adjusting pH, to take affect before planting. This also allows time for organic matter added to the soil to begin breaking down.

Established Gardens

• The structure and condition of your soil changes over time. The addition of fertilizers and organic matter, and the process of growing vegetables alter the nutrient balance in the soil. The soil pH may also change over time. Testing the soil every two to three years and making the necessary adjustments keeps your garden soil productive. Fall testing is recommended, but spring testing can be done. Keep in mind that if your soil needs major adjustments to the pH that it may take several months for the desired result to become evident in the soil. Simple adjustments, such as the addition of fertilizer, may take effect more quickly.

Special Circumstances

• Sometimes plant growth offers you a clue that your soil needs testing. Stunted growth, yellowed leaves and discolored foliage on your vegetables may indicate the lack of one or more nutrients in the soil. Typically, yellowed leaves on the bottom of the plant with pale green foliage on the newer leaves indicates a nitrogen deficiency. Blossom end rot and distorted new leaves may be a sign of a lack of calcium. The appearance of burnt leaf tips and older leaves that turn dark green or purplish are signs of a phosphorous deficiency. A potassium deficiency may cause the leaves to yellow. A nutrient deficiency in plants may be the result of insufficient nutrients in the soil, inadequate watering or an improper pH level for the plant. Testing the soil to determine the cause of poor growth allows you to make the necessary corrections.

Considerations

• Sometimes, a quick soil test with a home soil-testing kit is all you need to determine whether growth problems are from a nutrient deficiency. If your soil lacks nitrogen, phosphorous or potassium, a simple application of fertilizer may be all that's needed to correct the problem. Establishing a routine of testing your garden soil via testing services every two to three years and completing a quick home test whenever you observe signs of nutrient deficiencies or poor growth will keep in you informed about the condition of your soil.

pH Concerns

• All vegetables have a preferred range of pH. Most vegetable preferences fall within the 6.0 to 6.8 range, but there are some exceptions. For example, potatoes (Solanum tuberosum) prefer a soil pH between 4.8 and 5.5 and become scabby when the soil pH is above 6.0. Growing varieties resistant to scab is often recommended. Alternatively, you can adjust the pH in one corner of the garden, or create a new bed specifically for growing potatoes. When testing and adjusting soil pH, always consider the needs of the vegetables you intend to grow in that area.