The Importance of Soil Sampling

Howdy folks,

I know that I have mentioned it a time or two but I would like to visit the topic of soil sampling.

Pulling Soil Samples

Michael on the left and yours truly on the right at Watford Farms.

When most folks look at soil they say “Oh yeah, that’s dirt, its everywhere, no big deal.” What most people do not think about is that the ground beneath their feet is what agriculture is founded upon.

The definition given for soils from Soil Taxonomy, second edition is—“Soil – soil is a natural body comprised of solids (minerals and organic matter), liquid, and gases that occurs on the land surface, occupies space, and is characterized by one or both of the following: horizons, or layers, that are distinguishable from the initial material as a result of additions, losses, transfers, and transformations of energy and matter or the ability to support rooted plants in a natural environment.”

Shwoo, that’s a mouthful!

Basically in VERY over-simplified terms from an agronomic standpoint, soil supports plants and thus allows farmers to grow crops which provide the food that we need to survive and prosper.

Sometimes the soil needs amendments (additional nutrients or other materials that change the pH of the soil such as lime and sulfur) to meet the specific needs of the crops that are being grown.

Great…so how do we know which amendments to add?

Well I’m glad you asked!

The first step is to determine what crop will be grown on a particular location. If the crop is a perennial grass, such as Bahiagrass or Bermudagrass for pastures or hay patches, samples should be taken at a depth of 2-3 inches. Grasses have a shallow fibrous root system and samples taken below the root system would be useless. If you are growing annual field crops such as cotton, soybeans, or peanuts the samples should be taken at a depth of 6-8 inches since these crops have a deep tap root system.

Soil Sampling

Making sure we are taking the samples at the right depth.

Ok, I know what crop I am going to grow and which field I am going to put it in, but how do I know where to collect the samples from?

Samples should be taken in a randomized zigzag pattern starting at one corner of the field and preceding to the other end of the field collecting the samples at the appropriate depths.  Once the samples have been collected using a soil probe, the soil should be well mixed in a bucket and poured into an appropriate soil box to be sent off for testing (contact your local Cooperative Extension System Office for soil boxes and sample information sheets. The boxes will have directions to where the samples need to be mailed). Each soil box should represent 10 acres unless different soil types are encountered within those 10 acres. If this should happen, take samples of both soil types and place them in separate boxes.

Soil Samples

With the same soil type, use one box per every 10 acres.

Each crop has an optimum pH range. Recommendations will be made on your soil report instructing you what to do if your soils are out of range for the crops to be grown. Generally if the pH is too low for your crop limestone may be required to raise the pH. If the pH is too high, sulfur may be added to lower the pH. Usually, the soils in the southeastern part of the U.S. tend to be sandy and slightly acidic (unless you are in the Black Belt region).

Your report will also tell you what soil group you have, as well as the CEC (cation exchange capacity) for that group.  It will also give recommendations of how much nitrogen (N), Phosphate (P2O5), and Potash (K2O) to apply. Remember folks, water is the most important factor in crop growth and development. Without water, nothing else really matters. Behind water is having the correct soil pH. And lastly, but of no lesser importance, are nutrients for proper growth and development; pH is ranked above nutrients because the pH has to be correct for proper uptake of those nutrients by the plant.

With production cost as high as they are in today’s market, it just makes sense to take good soil samples. Sometimes success just has to happen from the ground up!

Please feel free to leave comments or ask questions, I’d love to discuss it with you.

Until next time, y’all keep your eye on the road and the greasy side down!


8 thoughts on “The Importance of Soil Sampling

  1. If Michael wasn’t one of my best friends, I’d have a serious issue with the fact he has on a Alabama shirt in these pictures.

  2. Now Jared, I have a small problem with what you said about the forage grasses and their root system. I will begin by saying that since you are not tilling a pasture, I agree with you saying that the soil sample should be taken at a shallow depth. Now here is the problem, you say that grasses have shallow, fibrous root systems. I agree that a good portion of their roots are shallow, however, they also have deep roots that are strong enough to penetrate the compaction zone in most south-eastern soils which is 6-8 inches deep. So even if you take the soil sample at the same depth as the cotton/soybean/peanut soil sample, you still will be in the realm of where nutrients can be taken up by the grasses.

    • Very true, T-Ray! I should have rephrased that. Bahiagrass does make a good rotation with peanuts and other tap rooted crops, such as cotton and soybeans, because of the root tip’s ability to withstand low levels of oxygen often encountered in hard pans. By penetrating through the hard pans, the Bahiagrass roots create macropores which promote better oxygen levels in the soil. It also allows for better water infiltration which is required for proper root development of the crops which are not tolerant to low oxygen levels in the root zone. If the root tip of a plant dies, such as cotton for example, the lateral roots will run parallel along the top of the hard pan which could result in lodging during harvest as well as the inability to take up water and nutrients during a drought.
      The point I was getting at in the post is that there is no need to take a sample on a permanent stand of grass deeper than 2-3 inches because you will not till the soil to incorporate the added amendments.
      Do you agree with my reasoning? I am open to suggestions or any advice. Thanks for stopping by!

      • Well said sir. I do agree that there is no need for the sampling to be done any deeper than 2-3 inches. You got a little deeper into the grasses and the things their roots do for other plants than I was going to get in to, but you are exactly right in what you said about them. Well played sir!! In my original post, I just wanted to say that forage grasses typically do have a good many roots that will go deeper and not stay shallow.

  3. yes,the importance of soil testing in Agriculture cannot be overemphasize as it plays a virtal role in lime and fertilizer recommedation.but the challenge is getting the poor and rural farmers to undergo these to enhance crop production

    • You are right! Although we see the benefits of soil sampling, it is still hard to make a certain few people see that times are changing along with the input costs that it requires to grow crops. You have got to keep an eye on your bottom line and applying lime and fertilizer to land that does not need it can be costly and can have adverse impacts on the particular crop that is being grown. I guess in the end though, people can say that soil testing is beneficial to crop production, but if they do not actually take a soil sample, then it was just a good thought. It is hard to produce a good crop on good thoughts… Thanks for stopping by!

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