A cover crop of winter rye will improve garden soil

The Detroit News

Every fall after the growing season is over, I continue my soil-building regime by planting a winter cover crop. You’ll sometimes hear cover crops used in this type of application referred to as a “plow-down” crop.

My tried-and-true cover crop is winter rye. Yep, the same grain crop that is used for rye bread and rye whiskey. It’s also known as field rye, cereal rye or just simply “rye.”

Winter rye (Secale cereale)  and annual ryegrass (Lolium multiflorum) are two completely different plants. While annual ryegrass is often grown as a cover crop, it will not survive freezing-cold temperatures so is not suitable for use as a winter cover crop. So don’t confuse the two.

As I mentioned earlier, rye is planted in the fall just like winter wheat. As a matter of fact, the two crops have almost identical cultural requirements. Rye however, is hardier and can be sown a bit later in the fall than wheat.

My winter rye seedlings are about two inches tall on Veteran’s Day.

One of the biggest advantages rye has for a farm or garden is its contribution to improving soil tilth.

Tilth refers to the physical condition of the soil as it relates to growing plants.

Soil is roughly divided into three types: granular, which is made of single grains such as found in sand; massive, which is made up of microscopic particles of clay compressed together; and aggregate, soil that has just the right sized clumps of soil adhered together.

Aggregated soils are loose, friable and porous allowing for good water drainage and plenty of aeration but still allowing nutrients to remain in the soil without being washed away. It’s the holy grail of soils that farmers and gardeners are hoping for.

Rye is able to germinate in relatively dry soil. So even though there wasn’t any rain after I planted, I still had a nice stand of seedlings.

Rye plants produce tremendously large and deep roots compared to most other cultivated plants.

As they grow, rye roots exert pressure on the soil itself that will compress aggregates together squeezing them into certain shapes depending on the size and chemical makeup of the soil particles. These distinct shapes can clearly be seen under a microscope. 

At the same time that the roots are doing the squeezing, they are also separating the compressed aggregates into smaller sub-structures. As the roots grow down through the soil, slightly different rates of dehydration happens between the tiny separated clumps of soil causing many minute cracks to open up in the clumps. This results in even more friable soil conditions.

In one part of the garden I spread the rye seed in dry grass stubble and lightly ran a tiller over it. This also produced a good stand of seedlings.

All plant roots have small structures called root hairs sticking out from them. The root hairs are responsible for the absorption of water and dissolved minerals from the soil substrate.

During active growth, these root hairs are constantly growing and dying and being replenished again over and over.

The dead root hair cells stimulate microbial activity that decomposes those dead root cells anaerobically into humus. Humus, among other things, acts as a kind of cement sticking together the sand particles found in granular soils. With additional humus, granular soils are able to retain more water and nutrients.

Interactions in soil are very complex but the takeaway is that cover crops have a profound effect on soil improvement. These improvements can be very apparent even after just one year.

I planted my rye during the last week of October. It might be a bit late to sow winter rye at this late date. However, with the warmer weather patterns being produced la Nina this year, a late planted crop of rye may still work. If you can coax a half-inch or so of growth out of your rye before the really cold weather sets in, you will see a good stand next spring - especially if we get a good cover of snow to blanket the crop.

Next spring the growing crop will be mowed while the stems are still green and tender at about 18 to 20 inches in height.

The resulting plant residue from the rye stems and leaves will decompose aerobically, adding compost (as opposed to humus) to the upper layer of the garden topsoil.

The improvement in next year’s soil will be noticeable as you plant and grow your crops and will continue to improve year after year.