Whether establishing a new garden or orchard or managing an existing planting, submitting a soil sample for analysis is an important step in sustainable food production. The results you obtain from this test will let you know if your soil has an appropriate pH for the crop you want to grow and offer recommendations of amendments necessary for optimal plant growth; they will also let you know if you can cut back on your fertilizer applications which will save you money and may result in greater yield.
Anyone growing fruits or vegetables should collect and submit a soil sample for testing every three to five years, more often if changing production systems or trying to identify the cause of poor plant growth and production.
A soil sample is a composite mixture of multiple sub-samples (10 to 15 should be sufficient for most home plantings). If your planting contains more than one soil type (different texture, color, drainage, etc.), then you should collect a separate sample of each.
Sub-samples should be collected randomly across the production area, to a depth of 6 to 8 inches. In perennial tree and vine crops you may want to collect a second sample as deep as 24 inches if you suspect severe subsoil problems; the root systems of these plants may extend 36 inches or more into the soil. Keep in mind however that amendments primarily affect just the upper soil layer; nutrients like phosphorus and potassium and amendments for adjusting pH like lime are not very mobile in the soil. Incorporating these amendments deeper in the soil is not an option for perennial plants because you want to avoid damaging their root systems.
A soil sample can be taken any time the soil is not frozen. It is best to submit samples in the fall or early spring so you have time to apply any necessary amendments before or early in the next growing season. Soil test values will vary by season; you will want to collect samples in subsequent years during the same season so results and recommendations can be compared.
For best results, collect samples when the soil is relatively dry rather than after a rain event or irrigation.
Soil pH and nutrient content have a direct effect on the health and productivity of fruit and vegetable plants. Submitting soil samples for testing will provide you with recommendations for amendments that can improve your soil quality.
Your results may indicate that you have been applying too much of certain nutrients. For example, excessive nitrogen in the soil will cause your plants to become excessively vegetative (lush green growth) with a negative effect on fruit yield and quality. Knowing this will allow you to reduce your fertilizer inputs, and therefore your annual input costs.
Use a soil probe, auger, spade, or shovel to collect sub-samples from 10 to 15 points across your production area. Make sure you sample from where the plant root systems are or will be (rather than from walkways, for example). Mix the sub-samples together in a clean plastic bucket, removing any large stones, vegetation, or other foreign material. You’ll need about two cups of soil to fill the lab-provided sample container.
Several labs in Nebraska offer soil testing. Midwest Laboratories in Omaha and AgSource in Lincoln are two options. Their websites contain information about requesting a soil sample test kit, which parameters they test for, and when you can expect to receive your results. The test will cost approximately $25 per sample.
Your soil test results will contain recommendations for soil amendments based on the garden or orchard crops you indicate on the sample submission form. If you have questions about interpreting your test results or which soil amendments will best meet the needs of your site and production system, contact your local Nebraska Extension office.
Most fruit and vegetable plants prefer an acidic soil pH. If your test results indicate that the soil’s pH is too high, elemental sulfur can be used to lower it. Just keep in mind that Nebraska’s clay soils have a high buffering capacity which means that their pH will immediately begin to rise after you add sulfur. To maintain the desired pH you may need to add sulfur every year or two.
For more information about managing soil and nutrients for vegetable production check out UNL’s Fertilizers for Vegetables in Home Gardens. The Midwest Home Fruit Production Guide is an excellent source of information about fruit production, including recommended fertilizer rates.