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Properly matching forage types to soil types can be a food-plot difference maker.

I have always been told that opposites attract. And as a general rule, it certainly seems as though couples with complimentary personalities build strong relationships. I am in no way trying to make myself out to be some sort of expert in match-making, but general observations over the years  seem to show that when the individual characteristics of each person within a relationship fit well together, the relationship works. If these characteristics or traits do not fit well together, it is a struggle to achieve harmony.

The value of proper combinations can be found elsewhere, too. The strongest steel results from the right combination of metals, the best tasting food from the best combination of ingredients and so on. In the world of food plots, there are many combinations that can affect the level of success. Planting the right forage variety based on the time of year you are hunting or determining food plot locations based on stand locations, prevalent wind direction, entry and exit routes, etc., can all greatly influence the amount of hunting success you will achieve with your food plots.

However, the most important combination to consider with food plots is matching the forage to the soil type in which you are planting. If this is not done properly, the rest of the combinations won’t matter because you won’t have a productive food plot from the beginning.

Soil Make-up

Soil is defined as the loose layer between the soil horizon (top of the ground) and the rock layer beneath, and is the area where plants grow and receive the vital elements for life. Soil consists of a mixture of organic materials, organic matter and various rock particles derived from the subsoil rock layer.

Organic material is the combination of once living organisms (plant, animal, insect, microorganisms) in varying stages of decomposition. Organic matter is the stable, fully decomposed fraction of organic material otherwise called humus. It is this portion that is an indicator of soil quality, with a higher humus content associated with healthier soil. Organic matter is important for several reasons, including microbial activity, nutrient supply and for water retention, because organic matter acts like a sponge, increasing the soil’s water-holding capacity.

The rock particle portion of the soil is directly influenced by the “parent” subsoil rock layer because it is the source of those minerals. If the rock layer is high in calcium, the soil will in turn tend to be high in calcium. The minerals found in the soil are utilized by the plants and forages growing therein. In general, the higher the mineral content and the higher the organic matter level in the soil, the more productive the soil.

It is little surprise that national soil maps show the highest mineral and organic matter levels are found in the most productive agricultural areas. Neither is it coincidental that areas with nutrient rich soils also generally have more B&C an P&Y whitetail entries than areas with poorer soil.

Determining Soil Type

Soil is comprised of three basic components: clay, silt and sand. While some soils are made up of only one of these elements, most are a combination of two or three. Clay consists of the finest particle size of the three basic soil types, which allows it to compact tightly and hold moisture. Predominant clay soil, however, does not necessarily “hold” moisture within the soil but rather the clay acts like a barrier holding moisture out. What moisture does make its way into the clay soil is often bound by the fine particles.

Ridges that have a high percentage of clay tend to have more moisture runoff as opposed to moisture absorption, and lowland areas that are high in clay or have a clay sub-layer have a tendency to stay wet and have poor drainage.

Sand contains the largest particle size and is highly moisture permeable. This characteristic results in a high amount of leaching of both moisture and soil nutrients.

Silt consists of a particle size that is between clay and sand and is typically associated with water runoff or creeks and rivers, but can be found in many areas.

A fourth soil category is loam, which is a combination of the three basic soil types. Loam can be broken down into subcategories such as sandy loam, clay loam or silt loam. If the predominant soil type is sand but also contains some clay and silt, the soil is categorized as sandy loam. The same is true for clay or silt loam, with the type of subcategory loam determined by the predominance of the specific soil type. In general, loam and its subcategories are considered the most productive soil types in comparison to soils classified as strictly one soil type or even two soil types, such as sandy clay or silt clay.

The reason is that the combination of the three soil types provides individual soil type advantages that when blended together produce a soil more conducive to plant growth. For example, a clay loam has enough sand and silt along with the clay to allow for some water absorption, but then will hold moisture better than soil that is predominantly sand.

There are different methods that can be used to determine the specific soil type of your food plots. First, you can take a soil sample by probing multiple areas of the plot, combining them to get a collective representation then sending the sample to a soil lab for analysis. The lab will test the sample by evaluating the levels of clay, sand and silt, which will determine the specific soil type of your food plot.

A common tool used in this process is called a soil triangle, which is a triangular-shaped grid with each side representing one of the three basic soil types. Each side has values ranging from 0 to 100 percent. The percentages of clay, sand and silt from your soil sample will be placed in the grid to determine the exact soil type. While this is a great way to be very specific, it can also be costly, so many people use a second method of soil type classification, USDA soil maps. The USDA/NRCS (Natural Resources Conservation Service) have maps of the United States that show soil types that can be used to determine specific soil types on your property. While this method might not be as specific as a soil test of a particular plot, it is far more cost effective, while still maintaining a high level of accuracy. You can visit an NRCS office and talk to an agent or there are several websites (including the NRCS site) that can be used to view soil maps.

The soil types you will find using this service are identified by a specific name. For example, my farm contains the soil type called Sharpsburg Shelby, “Gently sloping to steep, moderately well-drained and well-drained upland soils containing silty clay loam or clay loam formed by glacial till or loess.”

A final and more primitive method of determining soil type is what I call the “dirt ball” method. While rudimentary, this test is fairly accurate and will at least help to quickly determine the likely soil type.

Take a handful of soil and make a ball. If the soil will not begin to form a ball shape it likely has very high sand content. If the soil forms a ball but easily loses its shape, the soil is likely a sandy loam soil. If the soil easily goes into a ball and when dry has a flour-like feel (silt) then the soil type is likely loam or silty loam. If the soil goes into a ball easily and maintains its shape, the soil type is probably clay loam. Finally, if the soil forms a hard ball that can be pressed flat and maintains its shape even when elongated, it is likely a clay soil type. 

Matching Forage to Soil Type

All food plot forages have unique growing characteristics that lend themselves to being more productive when planted in a specific type of soil. One of the most important of these characteristics is root structure and how it affects a plant’s ability to pull moisture from the soil. A highly popular perennial clover used in food plots is ladino clover. Ladino clover has a creeping root structure that does not grow very deep but rather spreads out horizontally, thickening the overall clover stand. Due to its structure, ladino clover requires a soil that has good water-holding capacity. From what we discussed earlier, we know that clay loam has good water holding capacity and therefore would make a good soil type to use for a ladino clover food plot.

Remember, however, that clay loam has a range based on the total percentage of clay versus sand and silt. A ridge classified as clay loam but is toward the higher side on clay, might not be as suitable for ladino clover because the heavy clay content results in less permeability of moisture in the soil and causes more water runoff. However, the same soil in a bottom or low-lying area might work well for ladino clover because runoff is not an issue. On a ridge, a silty clay loam might be a better soil for clover.

Alfalfa is another popular food plot perennial, but its root structure differs from that of ladino clover in that the roots can grow several feet deep.  Alfalfa does not respond well to “wet feet” and requires a well-drained soil such as sandy loam or sandy clay loam. Looking again at food plot topography to take in drainage considerations, an alfalfa field planted on a ridge would likely do well in a sandy clay loam but would do better in a sandy loam if the plot were in bottom ground.

Brassicas are another popular food plot planting used as a fall and winter food supply. Brassicas, especially tubers such as turnips, have a large and somewhat deep root structure. Like alfalfa, brassicas require well-drained soils and do not perform as well in soils that hold moisture.

To this point, I have a few fields on my farm that change in topography within the same field. The food plot starts out on a ridge, goes down a slope and ends in a low-lying bottom. When I planted these fields in brassicas, the normal result was larger more productive plants on the ridges where the soil was more well-drained and then a progressive decrease in productivity down the slope with the least productive area being in the bottom where the soil held moisture. Realizing this, I now plant only brassicas in those fields on the ridges. However, that does not mean that brassicas cannot be planted in bottom fields. Remember, soil type is the most important factor and in the bottoms where I have well-drained sandy loam, brassicas do fantastic.

Another comparison between two common food plot forages would be oats and wheat. Wheat does best in well-drained soil and while oats can do OK in a well-drained soil, they perform better than wheat in heavier soils. Most food plot forages have guides listing the best type of soil in which to plant. There are many other resources you can use including your local agronomy extension office.

The wild card in all of this is rainfall. During a year with above average rainfall, a soil type not conducive to shallow-rooted forages might produce fine and vice versa a drier than normal year might produce good alfalfa or brassicas in a more poorly drained soil. Since we cannot predict the weather, your best bet is to match the soil type to the right forage based on normal rainfall.

Conclusion

Without compatibility, you set yourself up for failure. That is true with most things in life and certainly true when it comes to matching forage varieties to the types of soils found in your food plots. Don’t try and force something that is destined to end in failure. There are many food plot forage varieties available and certainly one that will fit your situation. A little bit of research regarding soil types and then the right food plot forage to plant in it will at a minimum start you down the road to food plot success.

— Matt Harper is an avid whitetail hunter and food plot expert from Iowa.

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