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Are we facing a corn silage disaster?

Mark Boggess for Progressive Forage Published on 31 May 2019
Corn field

Those of you who have followed my articles know that I like to illuminate the complex challenges facing forage and livestock producers. Like you, I would prefer things were simpler, but unfortunately, just the opposite seems to be happening.

Consequently, at USDA Agricultural Research Service (ARS), we are more and more focused on understanding complex biological systems, with a keen eye on our goals of increasing the production, efficiency and value of agricultural systems and agricultural products.

One way we are now trying to simplify and better understand these systems is by separating the primary effects influencing a production system into four categories: genetic (G), environment (E), management (M) and socioeconomic (S), or GEMS. The moral here is there are things we can control, or at least influence, such as genetics and nutrition, but many that we can’t, such as weather. But all of these effects have an impact on the production system and on how we need to prescribe best management practices. And unfortunately, even for a crop as relatively simple as corn silage, the GEMS-level complexities continue to increase.

Let’s start with the good and great.

Good: Corn silage production is relatively straightforward. Using modern practices and production systems, growing corn silage is efficient, productive and comparably profitable. Improved varieties are available that continually produce impressive yields, along with weed and pest control, fertilizers, technology and equipment. The corn industry is well-supported, and these production factors are increasingly improved year after year.

Great: For the dairyman or feedlot producer, when managed properly, corn silage provides a high-yield, comparatively inexpensive forage that is easy to harvest, store and feed, while producing excellent performance. There are other options for the producer, but none that combine all of the efficiencies, benefits and production capacity afforded by corn silage. And it’s very rewarding to watch a high-producing dairy cow, or a healthy, fast-growing feedlot steer dig into a bunk full of corn silage.

So, what is the problem?

Well, let’s start on the ground. Corn, particularly corn silage, is hard on your soil. High-yielding corn silage requires a lot of nutrients that even a healthy soil can’t provide indefinitely. Consequently, corn silage production requires aggressive inputs of manure or other soil amendments and/or commercial fertilizers. And even under the best of management practices, soil carbon is steadily decreased over time in a corn silage system.

Research has shown in Iowa that a conventional corn-soybean rotation under moderate tillage loses 1,000 pounds of carbon per acre per year, and under corn silage, we could expect even greater losses. This loss of soil carbon reduces the soil’s ability to capture rainfall and store nutrients and leads to the production system being more dependent on external inputs to maintain economic levels of production.

Second, soil erosion continues to be a great challenge for agriculture, and corn production is certainly part of the problem. At our USDA-ARS National Laboratory for Agriculture and the Environment (NLAE) in Ames, Iowa, scientists study the relationships between crop production and environmental factors such as soil erosion. NLAE research on corn production across the U.S. has shown that, on average, for every pound of corn grain harvested, we suffer 1 pound of net soil loss. Think about that on the scale of corn production we now have across the country. An acre of corn yielding 200 bushels at 56 pounds per acre is losing almost 6 tons of soil annually. It is not a stretch to conclude that erosion rates for corn silage are higher yet, and it is also easy to see this situation is not sustainable.

These concerns have my attention. At the U.S. Meat Animal Research Center (USMARC), we produce a lot of corn and corn silage for our animal research herds. So as producers, what can we do? How can we continue to realize the value of corn silage in the feedbunk but do a better job environmentally?

There are no easy answers to that question, but I would start by saying conventional cover crops are certainly beneficial, and there are many options available. Use of cover crops is not perfect and can be cost-prohibitive, but it is a great place to start when considering sustainability factors on the farm.

Strategies for improvement

However, in addition to traditional cover crops, there are two other strategies being developed in ARS that are showing great promise. The first is a corn silage management system where alfalfa is interseeded directly into the corn crop. This strategy is being developed by ARS scientists at the U.S. Dairy Forage Research Center in Madison, Wisconsin. The approach is relatively simple. Alfalfa is planted between the rows of corn in the spring.

The growing alfalfa is then treated with a growth inhibitor, which retards the forage growth and reduces competition with the corn from the alfalfa. However, the growth retardant does not prevent the alfalfa from aggressively developing roots. The alfalfa also fixes some nitrogen (N), which is available for the corn crop. In the fall, the corn is cut for silage, leaving the alfalfa stand as a cover crop, which then produces a mature alfalfa crop the following spring. This approach is still under development, but the proof of concept has been established, and it is now being tested across the U.S.

The second strategy is the development of a kura clover living mulch under the corn crop. USDA-ARS scientists at the Soil and Water Management Unit in Saint Paul, Minnesota, along with collaborators at University of Wisconsin and University of Minnesota, have been working on this idea for several years with very encouraging results.

Kura clover is a bit tricky to establish and manage, but once established, it is a vegetatively spreading legume that fixes nitrogen, prevents weeds and improves water use efficiency. It is also winter-hardy and has the ability to survive harsh agronomic management. Kura clover’s N-fixing ability and dense mat of roots significantly reduce N application requirements for corn (up to 100 percent in year one and 40 to 60 percent in year two and later), while protecting against soil erosion and capturing excess N in the soil.

Water infiltration rates in the kura clover living mulch are eight to 10 times higher than corn, significantly improving water use and water use efficiency. There are other benefits relating to soil health and soil dynamics that are not yet well defined.

Current management recommendations suggest 5 to 8 pounds of seed per acre for initial seeding, with three years until full maturity. Corn can be interseeded in year two and every year after, if managed carefully. Corn is planted in strips that received a band application of herbicide or were rotary tilled to provide adequate space for the corn seed. The clover rhizomes then fill back in under the corn canopy, restoring the living mulch.

Kura clover can also be managed as a forage for either harvest or grazing and is equal or superior to alfalfa quality, with about 80 percent of the yield potential. As a forage, kura clover thrives and produces best yield potential when grazed or harvested aggressively three to five times annually. In dry years, there can be some yield drag on the corn crop, but the overall benefits are positive, and yields are similar to conventional corn with adequate moisture or with irrigation. The only really bad news is that kura clover seed is currently very difficult to find.

In summary, there is certainly more work to be done to enable widespread adoption of interseeded alfalfa and kura clover mulch, but these strategies are well-developed and show tremendous potential to provide economically viable options for forage and livestock producers. At USMARC, we are developing plans to evaluate both of these options with an eye on improving the efficiency of our integrated livestock systems, as well as our soil health and environmental sustainability. I am sure we will have a steep learning curve, but we are anxious to get started. We’ll keep you posted.  end mark

PHOTO: Use of cover crops is not perfect and can be cost-prohibitive, but it is a great place to start when considering sustainability factors on the farm. Photo by Lynn Jaynes.

Mark Boggess
  • Mark Boggess

  • Director
  • U.S. Meat Animal Research Center – Clay, Nebraska
  • Email Mark Boggess