Q1: What is a soil test?

A: A Soil Test is a process by which nutrients are chemically removed from the soil and measured for their plant available content within the sample.  The quantity of available nutrients in the sample determines the amount of fertilizers needed for a particular crop.  A soil test also measures pH and the amount of acidity within the soil to determine if lime is needed and how much should be applied.

 Q2: How often should a soil be tested?

 A: A soil test should be conducted if fertilizer is going to be applied or when problems occur during the growing season. Once every year is recommended when nitrogen fertilizer is applied, and at least once every three years if P and K are concerned.

 Q3: When is the best time to take soil samples?      

 A: Soil samples can be taken any time throughout the year for checking pH, phosphorus and potassium status.  Collect soil samples 3-6 months before planting. Early spring is a good time to take soil samples for summer crops, and summer is a good time to sample for fall and winter crops.  This allows time for lime recommended to react and change the pH before the crop is planted. To assess soil available nitrogen, sample as close to planting as possible. For Lawns, the late spring (May) is a good time sample for warm season grass and the summer (mid-Aug) is good for cool-season grasses.

 Q4: What tools and suppliess are needed to take a soil sample?

 A: A clean plastic bucket, and a soil probe are needed.  You also need soil bags (Both soil probe and bags can be obtained from your local County Extension Service office).  Specify the crop you wish to grow and a yield goal (for some crops) you try to achieve on the sample tag in order to get lime and fertilizer recommendations.

 Q5: How should a soil sample be taken?              

A: Collect a core with a probe or a slice with other tools of soil to 6 inch-deep from 15-20 random locations across the sampling area.  Different areas of the field may need to be sampled and labeled separately.  Example:  FRONT, BACK, SIDE of the house.  For most garden areas one sample/plot should be adequate.  Mix those cores thoroughly before placing in a sample bag. For more information please Check F-2207 How to Collect a Good Soil Sample. and PT 2003-5   SOP for Collecting and Handling Soil Samples in Oklahoma.

 Q6: Can samples be taken when soils are wet?

 A: Soil moisture does not affect the test results since samples are dried before they are analyzed.  However, extremely wet soils are difficult to collect and mix.  Therefore, allow soils to drain before sampling.  Soils too dry are normally hard to get the right depth.

 Q7: Where can I buy soil sampling probes?             

 A: The following companies sale soil sampling tools:

1.  Oakfield Apparatus Inc. 920-583-4114 (voice) 920-583-4166 (fax)

2. AMS 1-800-635-7330

3. Our Lab can sell you a soil sampling probe (T-Bar Style) for $45/ea.

 Q8: Where can I buy forage sampling tools?

 A: A portable hay probe can be purchased from Bill Jordan: 405-238-1740 or bjordan@brightok.net

 When the probe is not in use (about 24" long and 2.5" thick)

The probe is assembled for use.

     More selections of forage sampling tools can be found on National Forage Testing Association Website

Q9. How to set a realistic yield goal?

A: Aim for above average yields so crop yields will slowly increase over time. Keep a good production record of each field on the farm for at least five years. Some fields may produce more than others because of differences in soil quality and other factors. Adjust the past average to set a yield goal. The practical range for a yield goal should be somewhere above average to near the maximum yield in the last 3 to 5 years. Two common methods for calculating realistic yield goals are: 1) to add 10 to 30% to the recent average yield; 2) to take the average of the 3 highest yields in the last 5 consecutive years. These two methods are illustrated in the following table. Regardless of the method you employ it is important to be consistent from one year to the next.

Q10. How to Handle Animal Manure Samples?

1. A: Manure samples can come in different forms: solid, liquid, or slurry. They need to be handled properly to ensure safe shipment to the laboratory.
2. Solid samples: Place about 1 pound of representative solid sample, such as poultry litter and feedlot manure, in a quart sized plastic bag. Do not use soil or forage bags for manure samples because some nutrients may be lost before testing. Put completed sample label on the bag and place it in a second plastic bag the same size or larger for extra safety.
3. Liquid or slurry samples: Liquid and slurry samples should be placed in a quart sized plastic bottle with a screw top lid (it can be ordered from the lab).  Do not use glass bottle since it may break. Bottle should be filled at least half way with representative sample.  Screw lid on tightly.   Put sample label on the bottle and place the container in a zip-lock plastic bag.    
4. Use cardboard boxes to ship sample bottles and bags.  Pack the box tightly with expanded Styrofoam peanuts or shredded paper and seal with strapping tape. Ship samples to the laboratory as soon as possible.
5.        Preservatives are generally not needed for manure samples used for fertilizer recommendations. 

Back to Top