Get the Most Out of Cover Crops

August 25, 2020

by Jeff Pastoor, Beef Technical Consultant

Cover crops have continued to grow in popularity over the last 10-15 years, and they can be a win/win for the producer that has both a cropping enterprise as well as a cattle enterprise.

Cover crops have many agronomic benefits. The term cover crop comes from their earliest intended benefit of reducing soil erosion on crop ground by covering the ground to absorb rainfall and to hold the soil in place with its roots. This saves soil for the farmer and improves water quality at the same time. When legumes are used in a cover crop mix, fertilizer costs can be reduced due to nitrogen-fixing. Organic matter in the soil is greatly improved by the use of cover crops. The root growth below ground is about equal to the forage growth above ground, so even when chopped for feed cover crops can contribute to the organic matter in the soil. This increase in soil organic matter greatly improves the water holding capacity of the soil as well as improving the overall soil fertility. Some cover crops, such as turnips and radishes, are effective in breaking up compaction to allow more oxygen to the root level, to allow the soil to work up better, as well as improving the water holding capacity. When used intensively, some producers have been able to reduce or eliminate the need for herbicides by having cover crops crowd out undesirable weeds; some cover crops even have natural herbicidal effects through root exudates. Cover crops can even reduce or eliminate the need for pesticides by acting as hosts for beneficial insects that then act as predators to harmful insects. Some cover crops also host beneficial microbes or produce compounds that discourage diseases and pests such as nematodes. In addition, to cover crops, producers can improve soil health through the use of QLF Agronomy products such as L-CBF Boost, which excel in feeding the soil biome.

Cover crops can also be a valuable feed resource for the cattle operation. Small grain silages typically have a TDN and protein level that is ideal for cow gestation rations. These small grain silages can also be used in lactation rations, usually along with some corn silage and some additional protein.

Cover crops can be grazed in either the fall or the spring, by either the cow herd or stocker calves. ISU research showed that at a stocking rate of 1.5 head/acre stocker calves could get 20-27 days of spring grazing or 8-13 days of fall grazing on small grain cover crops, with gains comparable to summer pasture. Many producers have very successfully grazed off the cover crop in the fall and were then able to harvest a good crop of silage again in the spring.

Cover crops can be a very cost-effective feed source. A client I work with wanted to calculate his cost for using the cover crop in his cow rations. He figured the soybeans he would grow on those acres would pay for the ground, so that didn’t get figured in. He had all of the expenses for drilling the cover crop, for fertilizing the cover crop, for harvesting and bagging the cover crop, and the total tons he harvested. His calculations showed that the rye silage he put up cost him $18/ton, and that allowed us to formulate a gestation ration that would maintain BCS for 88 cents/cow/day.

Cover crops can work well in grower rations, but we need to be careful using them in finish rations as the effective fiber of small grain silages is much lower than dry hay, and the primary need for forage in a finishing diet is to supply effective fiber.

Depending on the schedule for the next crop that needs to be planted, producers would have some flexibility of when to harvest cover crops in order to meet nutritional needs. If they mainly need tons of medium quality forage, then they can allow the cover crop to mature a little more; if they are needing higher energy and protein levels to help support cow lactation then they can harvest cover crops sooner when they are less mature.

There are some potential problems with feeding cover crops that can be avoided by properly balancing the ration fed to the cattle. The most common challenge is that cover crops can be very wet. With some cover crops, cattle could reach a gut fill of water before eating enough dry matter to maintain TDN intake. Also, the wetness increases the rate of passage making it more difficult for the cattle to absorb the nutrients on the way through the animal – this would not only affect energy and protein digestion but also mineral and trace mineral availability. Feeding some dry forage to cattle grazing cover crops, or adding some dry ground hay to a TMR based on cover crops can be a real benefit.

Some species of plants that make good cover crops can actually be toxic to cattle. Examples of toxic cover crops include Hairy Vetch, some species of Lupines (avoid Silky, Tailcup, Velvet, Silvery, Summer and Sulfur lupines) and some species of Amaranth (avoid Spiny amaranth, Redroot Pigweed, and Palmer Amaranth); several of these are also considered weed species in many row crop areas.

Many cover crops are nitrogen accumulators, which means they have the potential to cause nitrate toxicity. To avoid nitrate toxicity, sample feedstuffs before feeding, don’t force the cattle to graze the crop down too close to the ground, and ensiling crops will reduce the nitrate levels to about half.

Forage sorghums, sorghum/sudan grasses, and some millets can cause prussic acid poisoning.  Rotational or strip grazing can reduce this risk. Allow sorghums to grow past 24 inches and millets past 18 inches tall before turning cattle in. Do not graze or harvest prussic acid plants for 10 days after a killing frost.

Legumes are well known for their bloat risk. Some small grains can also cause bloat, especially if grazed after the heads have filled out. Small grains, being grasses, can also cause grass tetany in lactating cows.

To get the most out of your cover crops, be sure to work with your local QLF Representative or Consultant to ensure that the ration you feed will get the most out of the crop you have harvested and the cattle you are feeding it to.


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