Timely Topics
Spring has arrived and many folks are thinking about improving their landscapes and fields. A soil test can provide information on the proper amount of lime and fertilizer to apply to your soil to optimize the soil environment for what you want to grow. Applying the correct amounts of lime and/ or fertilizer at the appropriate time minimizes nutrient runoff into surface or ground water, money is saved, and plant health is optimized. Soil testing can also help diagnose common nutrient deficiencies for plants that are growing poorly.
The reliability of the soil test, however, can be no better than the sample you submit. For results you can depend on, it is vitally important that you take samples correctly to accurately represent the soil in your landscape.
To collect samples, use stainless steel or chromeplated soil probe, hand garden trowel, shovel or spade. Do not use brass, bronze, or galvanized tools because they will contaminate samples with copper and/or zinc.
Mix soil samples in a clean, plastic bucket. If the bucket has been used to hold fertilizer or other chemicals, wash and rinse it thoroughly before using it for soil samples. Even a small amount of lime or fertilizer transferred from the sampling tools to the soil can seriously contaminate the sample and produce inaccurate results.
Sampling well in advance of planting will allow time for applied soil amendments to begin making the desired adjustments in soil pH or nutrient levels. Adjusting soil pH (which is raised with lime or lowered with acidic soil amendments) takes some months to fully react but fertilizers containing nitrogen, phosphorus, or potassium react in the soil and become available to plants much more quickly.
Established areas of lawns, trees, shrubbery, and other perennials can be sampled any time of year; however, an ideal time to take samples is when the garden season has ended in the late summer to early fall. Sampling in the fall allows time for corrective pH and nutrient management before new growth starts in the spring. However, the adage “better late than never” applies here and it is better to take a soil test now than not at all.
For areas recently limed or fertilized, delay sampling at least six to eight weeks to allow those amendments to take effect.
A good soil sample should be drawn from numerous sub-samples taken from the area to be tested, so a soil that is too wet will be impossible to mix together. As a rule, if the soil is too wet to work (or is good for making mud pies), it is too wet to sample. Another way to judge is to squeeze soil into a ball. If it easily breaks apart, then the soil can be sampled.
How often should a soil be tested? The sandy soils do not hold nutrients as long as other soils and are more likely to become acid through the addition of nitrogen but sandy soils are not common in Rockbridge. The nutrient levels in the silt and clay loam soils typical of Rockbridge change less rapidly with lime and fertilizer applications. In these areas, soil testing once every three to five years is usually sufficient.
For more information on getting your soil tested through the Virginia Tech soil testing laboratory contact the Rockbridge Extension Office at (540) 463-4734 or email [email protected].
