Soil Sampling And Testing
DR. NUTIFAFA ADOTEY
JACKSON, TENN.
Planning to get the most out of your crop next spring? Soil testing after post-harvest is a valuable step in accomplishing this goal. While soil testing is the only practical means to adequately evaluate the nutritional needs in a field to prescribe appropriate lime and fertilizer recommendations, the reliability of soil test results depends on the quality of the sample submitted to the soil testing laboratory. Poor sampling can result in inaccurate soil test results and produce unreliable lime and fertilizer recommendations. Some helpful soil sampling information:
Soil samples can be collected at any time, but some soil properties (soil pH, phosphorus (P), and potassium (K), for example) can vary depending on the time of sampling.
While soil test results from University of Tennessee Soil, Plant, & Pest Center come back within 3 to 5 days, it is best to sample months ahead of planting to allow for planning and getting prices on lime or fertilizer.
A good rule of thumb for soil sampling is to collect samples in a way that adequately represents the soil in that field. A well represented sample will consist of 10 – 20 core samples taken at the appropriate depth within a 5/10-acre grid.
University of Tennessee Soil, Plant, & Pest Center as well as commercial soil testing laboratories in Tennessee recommend taking soil samples to a depth of 6 inches.
The frequency of soil testing depends on cropping intensities, soil types, fertilization rate, tillage methods, and weather conditions; however, fields should be tested every two to three year to estimate the residual nutrient levels. For high-value cash crops (tobacco, vegetables, etc.) soils should be tested annually.
Soil testing is also recommended any time a nutrient deficiency problem is suspected or at the beginning of different crop rotation system.
Soil samples and a completed soil information sheet can be taken to your county Extension office or directly sent to University of Tennessee Soil, Plant, & Pest Center, Nashville. ∆
DR. NUTIFAFA ADOTEY: Soil and Nutrient Management Extension Specialist, University of Tennessee