18 March 2014

5 minute read

The topic of cover crops has been getting lots of discussion, writes Jim Paulson, Extension Educator at the University of Missouri.

Cover crops are not new but we are certainly looking more at their benefits in recent years. Green manure crops were an early method to add nitrogen to the soil.

Jim Paulson: "Cover crops work best when included in a whole farm cropping system."

Ten to 15 years ago, planting a cover crop such as winter rye following a corn silage harvest was used to reduce erosion on mostly bare ground. We now realize the benefits of rooting depth to break up soil's hard pan and how roots bring microbial activity to the soil. Cover crops can also fix nitrogen or scavenge nitrogen in the soil while adding organic matter and ground cover, improving water holding capacity and providing forage for livestock.

Cover crops work best when included in a whole farm cropping system. Cover crops can provide additional forage supply to a livestock farm when used as hay, silage, baleage or grazed in rotation while still providing the other benefits as well. But the questions that need to be considered are what and when. What cover crops provide the best forage? When will I plant? When and how to harvest? And, will this be profitable for me?

A variety of cover crops can work for forage. Which one you use may depend on when you want to plant it. Probably the most common scenario is to plant a cover crop following small grain harvest or corn silage harvest. This would be planted sometime from the middle of August to the middle of September. A cool season crop such as a small grain would be a likely choice. Do you plan to graze it in the fall or let it grow until spring and harvest it for silage, baleage or hay?

Here are some possible mixes and planting strategies to consider:

• Plant 1 to 2 bushels per acre of winter rye. This is a simple choice and usually a successful forage stand. Not the best for forage quality compared to other small grain choices. Grows tall but seldom out-yields other choices.
• My first choice for a fall seeding would be to use a winter triticale. It combines the hardiness of rye and the forage growth of wheat. Triticale yields comparably to other cereal grains and is usually the highest forage quality due to being less stem and more leaf. Winter wheat could be substituted as well. Plant at 1 to 2 bushels per acre at 1 to 2 inches deep. These mixes could be grazed in the fall or left until spring and harvested as a silage crop by Memorial Day and then same ground planted to corn for silage, soybeans or BMR sorghum-sudan.
• If you plan to fall graze for a lower cost feeding, plant spring oats in combination with turnips or even with tillage radishes, crimson clover and annual ryegrass. This can provide good yields of high quality forage. These forages are best grown in cooler seasons but will freeze out at the end of the growing season and not interfere in the spring. Seeding rates I would recommend are 1.5 bushels per acre of oats and 1 to 2 pounds of turnips. If you want to add more to the mix, I would use 5 pounds of radish, 10 pounds of crimson clover and/or 10 to 12 pounds of annual ryegrass.
• So why do we use these combinations? For fall seeding, we want to use cool season species. With adequate moisture, these species will grow much better in the fall and will even tolerate a light frost. Warm season species, such as BMR sorghum-sudan grass, millets, berseem clover and buckwheat will do best planted when the soil temperature is above 65 degrees F. They provide an early- to mid-summer seeding following a canning crop, after removing first crop hay on an old stand, winter killed fields, or other emergency forage situations. Suggested seeding rates are: 15 to 20 pounds for the millets and sorghum-sudan species, 20 to 25 pounds for buckwheat or 12 to 15 pounds for clover.

Mixes of different size seeds require certain considerations at planting. The best method is to use a drill with two different seed boxes and the ability to sow the small grain at an inch and a half deep while sowing the smaller seeds at a quarter to one half inch deep and pressed firmly. Research has been done to evaluate sowing both sizes of seeds together at one inch deep.

Depending on soil type, this may or may not be successful. A heavier soil type makes this a risky method because the smaller seed will not emerge from that depth. Broadcasting seed of different sizes is affected by seed weight and density.

Larger, heavier seeds tend to be distributed further from a cyclone seeder. Smaller and lighter seed do not carry as far and can be carried by the wind as well. The result can be streaking of seed with this type of seeding. Broadcasting seed, with or without light tillage, requires a higher seeding rate to obtain similar stand density. For these reasons, it is usually more successful to use a drill.

As always, working with your team of farm, nutrition and agronomy members will help to formulate a plan for your operation. These are guidelines to get started that hopefully will lead to a greater forage supply for your farm.