Soil testing measures the soil’s pH and nutrient levels and provides a basis for developing optimum fertilizer and lime recommendations.
Without soil testing, determining your correct fertilizer and lime recommendations is just a guess. Not knowing your soil’s nutrient status can result in either overspending for excess fertilizer or lime, or losing plant health and productivity.
Here is a step-by-step guide on how to collect a good soil sample, which you can send to Noble Research Institute. We process the samples and send them to a contract lab, which conducts the analyses. Noble Research Institute soils and crops consultants receive the lab data and make appropriate lime and fertilizer recommendations.
Sample most soils every two to three years. Sampling should be done more frequently for crops that remove large amounts of nutrients (hay or silage crops) or if nitrogen recommendations will be adjusted depending on soil nitrate levels. Soil nitrate levels are relevant for only a few months, where the other analyses are useful for several years.
Try to sample at the same time each year. Analyses data can vary depending on when the samples are taken. For example, soil test phosphorus and pH levels are higher in the spring than in the fall. Late winter is a good time to collect soil samples for summer crops, and summer is a good time to sample for fall and winter crops.
*A spade or shovel will do, but we recommend a probe because it saves time by collecting samples more quickly and efficiently, and collects a continuous core through the entire sampling depth with minimum soil disturbance. Here is a partial list of retailers that sell soil-testing probes .
Step 1: Order soil sample bags and sample information sheets by calling Noble Agricultural Testing Services: Soil Sampling at 580-224-6500 or print a form at bit.ly/soil-sample-form.
Step 2: Make a map of your property, note where each sample will be taken, and give the different fields unique names. Use the same field names each year so you can compare your results across time.
Step 3: Divide your property into sampling units in the following manner: Sample each field separately, no matter how small it is. For fields larger than 40 acres, subdivide these fields into smaller units. Sample areas separately if they are obviously different (bottomland vs. hills, areas that have been fertilized differently, etc), and sample problem areas separately.
Step 4: Confirm that your bucket and tool(s) are clean. Collect a core of the top 6 inches of soil at 15 to 20 random locations across each sampling area. Do not sample when it is too wet or dry because this can affect the depth of your sample. Make sure you collect the samples at random and do not sample just on ridges, sandy spots, etc. If you don’t have a soil probe, dig down 6 inches or more with a shovel, sharpshooter or spade. Trim the slice of soil that is collected with a knife or other cutting implement to a 6-inch depth and make sure the sample is the same width as its entire length. Remove any stones or sticks. Place the soil into the plastic bucket.
For additional information on collecting a soil sample with a shovel, watch our “How to Take a Soil Sample” video.
Step 5: Place all 15-20 soil cores collected from the field into the bucket and thoroughly mix to create one homogenous sample. Write the ID from your field map and other required information onto the sample bag, then put about a pint of the mixed soil into the bag. Simply scatter the remainder of the soil back into your field.
Step 6: Repeat sampling steps for each field.
Step 7: The following information is required for each sample: your name, address, email, field name and crop to be grown. If you want more customized recommendations, include your yield goal with this information.
Step 8: Mail your samples and completely filled information sheet(s) to: Ag Testing, Noble Research Institute, 2510 Sam Noble Pkwy, Ardmore, OK 73401
For more details on submitting your soil samples, go to www.noble.org/soil-sampling.
Eddie Funderburg, Ed.D., is a senior soils and crops consultant. Funderburg has broad experience in agriculture, soil testing, fertilization of forage crops and improved pasture management. He has conducted numerous research projects examining herbicides, fertilizer rates, sources, timing and soil test calibration.