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Managing winter rye cover crop as a forage

UW Extension
Properly manged, winter rye has multiple uses and benefits beyond conservation, including forage production, nutrient management and weed suppression.

Winter rye can be used as a cover crop after corn silage to protect against soil erosion, and in parts of Wisconsin is recommended by conservation planners.

Properly manged, it has multiple uses and benefits beyond conservation, including forage production, nutrient management and weed suppression. It can also provide a hedge against weather related forage shortage caused by alfalfa winterkill or drought.

Rye, planted in fall, can produce substantial dry matter (DM) yield the following spring, often without undue planting delay for the following crop. Rye harvested at the boot stage typically produces DM yield in the 2 to 3 ton per acre range at quality levels acceptable for many animal production groups.

Planting: Rye should be planted as soon after corn silage harvest as possible. In most parts of Wisconsin, rye planted in mid-to-late September produces higher forage yield, and tends to mature slightly earlier the next spring. However, yield potential does not significantly decline until October 10.

Later planting results in less soil cover going into winter, thus reducing soil protection. However, rye grows rapidly in spring and acceptable forage yield can usually be achieved with later October planting.

Seeding rates of 90 to 112 lb. per acre are needed for maximizing forage yield when rye is planted in a timely fashion. Published recommendations of 60 to 90 pounds are based on rye intended for grain production and will probably result in lower forage yields and insufficient soil cover. Seeding rate beyond 112 lb. per acre (2 bushel) may increase yield when rye is planted later than October 10 and will help to increase over-winter soil cover.

Harvest: Rye is harvested in boot stage to balance yield and quality, similar to oats. Boot stage is just before seed head emergence when the head can be felt near the top of the leaf whorl within the sheath of the flag leaf. 

Earlier harvest results in high quality but low tonnage and later harvest results in lower quality. Forage quality declines rapidly with increasing maturity beyond boot sage, 4 to 5 relative forage quality (RFQ) points per day, making timely harvest critical.

Also, boot stage is short, lasting only a few days. To optimize both yield and stage, well before the flag leaf splits and heads begin to show.

Boot stage typically occurs by mid-May in southern Wisconsin, but can vary, depending on growing conditions. This can complicate planning, especially if harvest involves custom operators and may delay planting of the summer crop.

This is also a period with high probability for rainfall in Wisconsin, potentially creating a problem with rapid quality decline if harvest is delayed. Practical experience suggests rye should be harvested early if long-term forecasts predict a wet period in the future.

Feeding considerations: Rye forage can contain high levels of potassium (K) which may limit its feeding flexibility in dairy rations. Date from the National Research Council shows average K levels of 3.34%, greater than most forages including alfalfa.

This increases concern about hypocalcemia (milk fever), especially given that its nutritional value is more suited to dry cow rations than lactation diets if harvested on the late side.

Care should also be taken because rye is a luxury feeder of K. Many farms have elevated soil test K levels which could lead to excessive K uptake. Wisconsin data has shown forage levels as high as 4.37% when rye was grown on soils exceeding 300 ppm K. Rye forage should be tested so K levels are known and rations adjusted accordingly.

When not to harvest: Variations in weather and maturity may make harvest of forage with satisfactory quality challenging in some years. Should delays prevent harvest at boot stage, termination with herbicide should be considered.

Conservation and nitrogen scavenging benefits will already have been realized, weed suppression potential improved, and an inventory of lower quality forage prevented. For more information on using a ray and other cover crop as a forage, visit: https://bit.ly/3b2rg9Z.