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PROBLEM SOILS

Cereal Rye is probably the best winter cereal for root mass, Problem Soils: Heavy Clay
and it grows at lower temperatures than other cereals. Black
Oats grow similar to white oats but have a much stronger Clay soils are a blessing and a curse! Clay has a very high
root system and seem to have a better soil aggregating effect. ability to hold water and plant nutrients, much higher than
Annual Ryegrass is a true star when it comes to improve- sand or silt. However, its small pore sizes restrict the move-
ment of compacted soils. It has a very dense root system, ment of air and water into the soil leading to low infiltration
and it is well adapted to heavy clay soils and poor aeration. and limited root depth. This combination of poor infiltration
Recent research by Murdock in Kentucky has shown that and poor root depth makes clay soils susceptible to water
annual ryegrass has root exudates that can actually dissolve deficiencies, even in high rainfall regions. Clay soils are also
fragipans, which are chemically cemented layers in the sub- sticky when wet and rock hard when dry. In the past, conven-
soil. Fragipans are found throughout much of the Southeast tional wisdom was to intensely till the soil to make it loose;
US and are very detrimental to crop growth. The research however, the result was the destruction of soil organic matter
indicated that annual ryegrass could dissolve about an inch (SOM) and soil aggregates, making the situation even worse.
of fragipan per year it is grown.
Some say that no-till won’t work on heavy clay soil. The truth
Warm-Season Species is, tillage doesn’t work very well either. The best remedy for
Sorghum-Sudangrass shines among warm-season grasses clay soil is to have plants growing as much as possible which
because it generates an absolutely enormous amount of high will add SOM and feed soil microbes that build aggregation.
energy root exudates that feed soil-aggregating microbes. Forming the clay into little balls (aggregates), around which
Okra has a very deep taproot and grows quite well in dense air and water can freely move, is the ultimate solution to im-
soils. Sunflower is famous for its deep taproots, but what is proving clay soil.
often ignored is just how fibrous the roots of a sunflower are
in addition to the depth. Pull a sunflower up and you will see We used to think the best way to increase SOM was to bring
just how enormous the root system is. Buckwheat has a very in manure from somewhere else, but this is an expensive pro-
small root system but has exudates with strong aggregating cess. What we have discovered recently is that SOM is best
ability. Sunn Hemp has a more vigorous taproot than most formed by two agents: microbes that feed on root exudates and
other summer annual legumes. mycorrhizal fungi, the benefits of which have been previously
described. It is essential for the growth of both mycorrhizal
Perennial Species fungi and rhizosphere microbes to maintain living roots for
Chicory has a very deep taproot and performs well on dense soil. as many days of the year as possible. This can be achieved by
Plantain seems to grow exceptionally well on soils so com- growing perennial crops or integrating cover crops between
pact no other plant seems to grow at all. the cash crops in a rotation. The cover crops and perennial
Eastern Gamagrass and Reed Canarygrass have a special- crops that tend to work well on heavy clay are the same ones
ized root tissue that allow them to grow on extremely dense previously listed that do well in compacted soils.
soils. Tall Fescue and Perennial Ryegrass are known for their
ability to grow well on compacted and heavy clay soils. In
drier areas, many wheat grasses can grow in compacted soils. Photo by Keith Berns

Photos by Dale Strickler Growing roots and soil biology cause soil aggregation which in turn makes high

clay soils much more productive!

“Stopped in today and got my seed. Please thank your staff for me.
Never have I met a better group of people. Absolutely amazing.
Left: Highly compacted, extremely dense soil with no roots penetrating below 18 Friendly, helpful, and just a pleasure from the minute we walked in
inches. Note the gray color due to lack of carbon and lack of oxygen being able to
move into the soil profile. Right: Same field after three years of Eastern gamma the door. Can’t wait to come back—I didn’t want to leave.”
grass production. Compaction layers are gone, roots are penetrating deep, oxygen Scott M, Canada
is moving freely, and productivity and infiltration rates are very high.

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