Vetch and oats as cover crops. Green manure crops (copy)

The recent cold weather brought a clear end to the growing season in Pennsylvania and has folks wondering if it is too late to plant cover crops.

The answer is no, there is still time within some limits.

The first limit is the species you choose to plant. Cereal rye is one good option for late planting, and another species that could do well is triticale.

Rye is very hardy and can germinate in temperatures as low as 34 degrees F. Growth will require temperatures of 38 degrees or higher.

An ideal time to get the rye in the ground is when the ground freezes overnight enough to hold the weight of the tractor but warms enough in the morning sun for the no-till drill to break through. Aim to plant the seed from 0.75 inch to 1.5 inches deep. When planting late it is best to increase your seeding rate to the 2- to 3-bushel-per-acre range.

Rye is the best cool-season cereal cover for absorbing unused soil nitrogen, according to the SARE publication “Managing Cover Crops Profitably.”

It has no taproot, but rye’s quick-growing, fibrous root system can take up and hold as much as 100 pounds of nitrogen per acre until spring, with 25 to 50 pounds per acre being more typical. Early seeding is better than late seeding for scavenging nitrogen.

A Maryland study credited rye with holding 60% of the residual nitrogen that could have leached from a silt loam soil following intentionally overfertilized corn. A Georgia study estimated rye captured from 69% to 100% of the residual nitrogen after a corn crop.

Rye increases the concentration of exchangeable potassium near the soil surface by bringing it up from lower in the soil profile.

Rye is one of the best cool-season cover crops for outcompeting weeds, especially small-seeded, light-sensitive annuals such as lambsquarters, redroot pigweed, velvetleaf, chickweed and foxtail.

Rye also suppresses many weeds allelopathically (as a natural herbicide), including dandelions and Canada thistle, and has been shown to inhibit germination of some triazine-resistant weeds.

Rye reduced total weed density an average of 78% when rye residue covered more than 90% of soil in a Maryland no-till study and by 99% in a California study.

Don’t expect complete weed control, however. You’ll probably need complementary weed management measures.

Leon Ressler is a Penn State Extension educator based in Lancaster County, Pennsylvania.


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