Soil Testing in Johnson County, Kansas
A soil test provides information on the basic fertility of soil. It is the starting point for determining how much and which fertilizers to use on a crop. Without a soil test, everyone is guessing at what the soil fertility level really is.
Proper collection of a representative soil sample is important for accuracy and analysis of test results. Follow these steps to obtain a good sample:
Decide if your field can be treated as one sample or needs to be broken down into separate smaller samples. If you believe the soil type, previous crop and fertilizer treatments are consistent across the field, treat it as one sample. If soil type and topography change across the field, different crops have been planted on different parts of the field, or there are problem spots, break the field down into smaller units to sample.
Using a soil probe or shovel, dig vertically to a depth of 6 inches for row crop samples and to 4 inches for pasture samples. If the available nitrogen, chloride, or sulphur tests are desired, a subsoil sample to 24 inches is necessary.
Take at least 10 – 15 samples from the field and mix the samples together in a clean, plastic container to create a representative sample. The more sub samples you take, the more assured you’ll be that soil test results are representative of your field. Bring approximately two cups of the mixed soil to the Johnson County Extension Office in a re-sealable, plastic bag.
Samples should be dry. You can let samples air dry, but do not use heat to dry your samples.
Bring or mail the soil sample(s) to:
Johnson County K-State Research and Extension,
11811 S. Sunset Dr. Suite 1500,
Olathe, KS 66061-7507
Office hours: Monday – Friday, 8:30 a.m. – 5:00 p.m.
We will need the following information:
Name, complete mailing address and phone number
Previous crop and its yield
Intended crop and a yield goal (indicate if this is a new seeding for pastures)
Previous lime application
The sample will be sent to the Soil Testing Laboratory at Kansas State University for analysis. Their results will be analyzed by our Agriculture agent here in Johnson County, and a report will be mailed to you.
The average time required to complete the analysis is 2 – 3 weeks. During the spring season, this turn-around time may take longer due to the increase in samples volume. Please take this into consideration in your planning.
A list of possible soil tests and their pricing includes:
Routine Fertility - $12
The test includes determinations for pH, lime requirement on those samples with a pH of 6.4 or less, available phosphorus and exchangeable potassium. On most soils, this test will be adequate. The results of the general fertility test may be supplemented by one or more of the tests listed below.
Profile Nitrogen - $3
This test is recommended on areas you believe have significant residual inorganic nitrogen (nitrates). Continuous heavy applications of commercial nitrogen fertilizer and/or heavy rates of manure may result in a buildup of nitrogen, especially where yields have not been proportional to the nitrogen applied. Because nitrates are water soluble, movement of the nitrates down in the profile will occur when moisture penetrates into the soil. Sampling for the available nitrogen test should include subsoil samples to depths deeper than the tillage layer. A surface soil sample (0 to 6 inches) plus a subsoil sample (6 to 24 inches) should be taken. The samples must be air dried as soon as possible to stop microbial activity. This means spreading the sample on a clean sheet of paper or plastic to dry before sending to the laboratory.
Organic Matter - $5
Organic matter in the soil is the storehouse of most of the nitrogen, sulfur, and several of the micronutrients. Organic matter results can be very meaningful to agronomists in better understanding the soil conditions on your farm. Organic matter levels can be useful in determining rates of herbicides. This test is not recommended on all samples, but only in cases where the additional information is desired.
Available Iron - $3
This test is recommended on the calcareous soils of the western part of the state to determine the likelihood of iron chlorosis on grain sorghum, soybeans, and corn. The test also can be beneficial for selection of shrubs, etc. around homes.
KCl Extractable Aluminum - $3
Extremely acid soils (pH of 5 or less) may contain appreciable KCl extractable aluminum, which is very toxic to plant roots. This test is recommended for use where extremely low pH's are found and lime is not immediately available for spreading. The test results are helpful in diagnosing problems of poor plant growth.
Profile Sulfate-Sulfur - $6
The majority of the sulfur in the soil is in the organic fraction and is microbially mineralized to the sulfate form for plant utilization. For interpretation of the sulfate-sulfur test, soil organic matter and texture also need to be known. Therefore, the organic matter test needs to be requested and texture reported on the information sheet. Sulfur deficiency is most likely to be found on low organic matter, very sandy soils. Samples should be to a depth of 24 inches.
Available Profile Chlorides - $6
Wheat has been shown to respond to chloride application. Because the chloride ion is quite soluble and, therefore, mobile, soil samples to a depth of 24 inches is recommended. No interpretation of profile chloride results are available for any crops other than wheat.
Available Zinc - $3
This test is recommended on areas with high yield potential for corn or soybeans, which by erosion, terracing, or leveling for irrigation have had the topsoil removed. Sandy soils, low in organic matter, under high yield conditions also should be checked for zinc. Wheat, alfalfa, grain sorghum, and pastures are not likely to respond to zinc so this test is not recommended for these crops.