The benefits and challenges of cover crops

Written by Dr. Jason Weirich on .

This time of year I like to assess the previous growing season and see what lessons we can bring forward. The 2016 planting season started early and finished fast for most of our territory. One thing I noticed is now that cover crops have become more popular, growers are finding a few management challenges to consider.

There have been a several factors driving the adoption of cover crops. There is an incentive from local farm agencies ranging from $20 to $35 per acre, depending on what county you are in and what cover crop mix you plant. There is also increasing evidence of weed-control benefits from cover crops. And finally, I see an increase in general conservation efforts focused on runoff prevention and soil quality. Dr. Kevin Bradley and his team with the University of Missouri have been looking at cover crops for the past few years to determine what weed control benefits producers are seeing (you can see their work here:

In the past, I have mentioned on this page that using Italian ryegrass as a cover crop is a bad idea. That still holds true today. Italian rye can become a major weed with the ability to evade common control tactics, including evolving into a multiple herbicide-resistant plant. Although its growth characteristics are ideal for cover crops, its cons outweigh the pros.

During the spring of 2016, growers ran into challenges with cover crops planted the previous year. Some producers were planting into standing rye, partially killed rye, dead rye, clovers, etc. You name it, someone was doing it. This year these efforts worked. They worked better than I thought they would. I saw several fields planted in challenging conditions that ended up with ideal crop stands, emergence and weed control. I also saw several fields that looked much less than ideal. I am a firm believer that you need to have cover on fields in the off-season. I believe that cover crops allow us to meet that objective. I am, however, in favor of killing that cover crop before planting into it.

Here’s why. Early in the spring, it can take a while for cover crops to die from herbicide applications. I had the chance to walk a field this year and see something that I have only read in textbooks: a recently planted corn field where the corn was emerging, then dampening off. Upon further investigation, I found the grower had terminated the cereal rye, waited two weeks, and then planted corn. The trouble was with the corn that got planted at the base of cereal rye plants. These corn seedlings were dying off. As I looked over the field, I noted that the cereal rye was still green at the base. Cereal rye has been documented to have an allelopathic effect on corn. My recommendation is to avoid cereal rye before corn—use a different cover crop to avoid the risk of a yield hit. Additionally, if cereal rye is used before going into a non-corn crop, make sure the cereal rye is killed at least two weeks before planting the crop—not just sprayed two weeks prior. The cover crop should be dead, and I mean graveyard dead.

Another aspect that may be overlooked after a flourishing cover crop are the effects it might have at harvest. Last fall I got the opportunity to see some of the on-the-go learning that comes with cover-crop management. When it comes to cover crops, harvest disruption is something you probably don’t hear about too much. In this case, a cereal rye crop was balling up, causing a slower harvest than one would like. Of course, this wasn’t by design, but it was a struggle nonetheless.

Yes, I am a firm believer in cover crops. I believe they bring multiple benefits. It’s not just a soil conservation benefit, but moisture, weed control and organic matter, too.

A cover crop rotation can bring benefits, but there will be lessons along the way. Right now, agronomically speaking, I think we may have more questions than answers, but I believe you should give them a try. Start on a small field. Your top choice might be a highly erodible parcel or a field with the low organic matter. It’s a place to start.

There are a lot of resources available online, but this one will lead you down the right path:

If you have any further questions, please feel free to visit with your local MFA or AGChoice location.

Know your soil's biological history

Written by Jason Worthington on .

If the topic of fungi, bacteria or other microbes comes up regarding crop production, we tend to think of them as something that might harm a crop. We think of pathogens, challenges to plant health and lower grain yield. That’s a natural thought process. From fungicides to varietal resistance and cultural practices, disease management is a top priority. On the flip side, we seldom think about how to impact our beneficial bacteria—but it appears that awareness is growing. And that’s a good evolution.

In 2015, Missouri had over 1.5 million acres of prevented planting. If much thought was given to how 2015 fallow acres impacted the 2016 crop, it was generally centered on keeping weeds under control. Another consideration was how to adjust soil fertility. But there wasn’t a great amount of consideration on what might have happened to beneficial microbe populations. In 2016 we were reminded just how important the beneficial microbes in our soil are, and prevented planting acres from 2015 may still impact cropping decisions in 2017.

There is a common term used by plant pathologists to describe the necessary components for a disease to exist. It’s called the disease triangle. The three sides of the triangle are: 1) the infectious agent; 2) a host plant; and 3) favorable conditions. Without any of the three sides, the triangle is incomplete, and a disease does not advance. The same goes for beneficial microbes. They are infectious agents requiring a host plant and favorable environment. The only difference is they provide benefit to the host rather than harm. In 2015, on prevented planting acres, the host plant was removed. The result, in many cases, was that beneficial microbe populations plummeted. One possible result of reduced microbe populations is a condition called fallow corn syndrome.

Fallow corn syndrome received a lot of attention in 2016. While there is little doubt that fallow corn syndrome existed, to what extent is debatable. Fallow corn syndrome can easily be confused with nutrient deficiencies in the soil, herbicide injuries and common conditions associated with cool, wet weather. Fallow corn syndrome is a phosphorous and zinc deficiency in corn growing in soil that has adequate levels of those nutrients. The plant is deficient of these nutrients due to an inability to retrieve phosphorous and zinc. This failure results from a significantly reduced population of mycorrhizae.

Mycorrhizae microbes work as an extension of the corn’s root system helping to reach and solubilize nutrients that are highly immobile in the soil. Mycorrhizae have the ability to colonize many different plant species and do not necessarily need corn as a host to maintain populations. Planting cover crops in fields that would otherwise lay fallow is one prevention measure, and weeds are a host that can support populations. The most likely locations where fallow corn syndrome may have existed fit some specific parameters. They were non-planted fields where growers actually did a good job of controlling weeds, didn’t plant a cover crop, and planted corn in 2016. The actual impact of fallow corn syndrome depends on how quickly mycorrhizae populations recover. Biological products like Quickroots or Cue (designed to either inoculate seed with mycorrhizae or stimulate growth and reproduction of beneficial microbes) may speed mycorrhizae population recovery.

An issue that may be more common in 2017 than 2016 is reduced soybean nodulation in fields that were fallow in 2015. Like mycorrhizae, rhizobia bacteria, which fixate N for soybean plants, form a symbiotic relationship with the crop. Unlike mycorrhizae, different rhizobia species are require specific plants to survive. Rhizobia japonicum, the species associated with soybeans, will not maintain adequate populations to provide significant nodulation when soybean plants are not present. While inoculating soybean seed annually is an excellent practice, it becomes increasingly important during extended absences of soybeans. Because crop rotations were disrupted with non-planted acres, there are fields this year that may be planted to soybeans for the first time since 2014.

As time pushes on, we tend to forget about the impact some weather deliver and how they can continue to affect our soil. Past cropping practices don’t just have longterm effects on things like the weed seed bank, or soil compaction. They also affect the biological activity of soil. As always we need to remember the needs of this crop year. However, it pays to remember what fields have endured past years and what we expect of them into the future.

New technology and new technique

Written by Dr. Jason Weirich on .

Back in April, I wrote about the use of new weed control technologies. We had just received approval from China for the Xtend trait. Just a few days after the election, we finally received federal registration for the use of XtendiMax with VaporGrip. With all of the media and publicity around off-target dicamba applications in the past season, these announcements could not have come fast enough. 

Proper stewardship of the new technology is a must—not only from a weed-resistance management or environmental perspective, but from a neighborly perspective. 

Xtend or Enlist will be tools that allow you to use a mode of action that hasn’t been used in soybeans or cotton in the past. And, it will show you if you have any off-target movement within a few hours or days. These new formulations are labeled for over-the-top or preplant applications to Xtend soybeans, but it’s not the same old dicamba formulations from the past—Banvel, Clarity, Detonate. Monsanto’s XtendiMax with VaporGrip, and BASF’s Engenia are two formulations that have considerably reduced the volatility of dicamba. 

These traits will provide you with new flexibility to control weeds, especially some of the difficult-to-manage herbicide-resistant weeds that have become prevalent in the MFA trade territory. 

But using the technology won’t be as simple as mixing herbicides in the past. This new trait will come with some new procedures as well. You will now be required to visit a website listed on the label to find out what products can go in the tank. Each manufacture or retailer has submitted a list of proposed tank mixes. These have been sent to an approved lab. This lab looks at several characteristics of the tank mix volatility, driftable fines, and compatibility to name a few.

Ken Carmack, adjuvant specialist for MFA, has been working with the top adjuvant manufacturers to develop MFA’s Crop Advantage lineup. This lineup is second-to-none. Rest assured when you see the approved Crop Advantage adjuvants on the list, they have been tested by our experienced field team. 

Drilling down in the specific requirements of this list, you will see that nothing is supposed to go in the tank unless it is listed on these websites. Some of the questions that I have received over the past few weeks are about the use of foliar nutritional products that may have gone in the tank in the past. Again, you want to make an application with any of the new cropping systems, Enlist of Xtend, you will need to follow the label and look at the website seven days before application. I would look at this as a living document. I believe the companies will add and remove different herbicides at any given time, albeit hopefully adding more than removing. You must check within seven days before application. 

I write this not to scare you from using these great tools, but to inform you about application requirements.

I am sure you will have plenty of opportunities to learn about this system, during the winter grower meetings that you attend. Please reach out to your local MFA for more information on MorSoy RXT soybeans and approved herbicides.

If you would like to hear about a specific topic or agronomy issue, please send me an email at This email address is being protected from spambots. You need JavaScript enabled to view it..

Variable yields call for variable rates

Written by Dr. Jason Weirich on .

What a year. From a drought to what seemed like we had moved to the rain forest, Midwest weather never seems to be consistent. Maybe that’s the new norm.

And like the weather, crops were variable. In the combine seat this fall, more than likely you watched the yield monitor read-out dramatically rise and fall as you worked across the field. While I hope the overall yield was good, the acre-by-acre results probably looked like the picture at right.

With variable yields like we saw over much of MFA’s trade territory this year, the amount of nutrient removal will be variable, too. It’s all based where you are in the field and what yield you made there.

This variability can cause problems for growers as you think about how to replace the phosphorus and potassium your crop removed. The old standby of flat-rating fertilizer like my grandpa did hasn’t proved itself as the best use of your fertilizer dollar. Variable-rate technology allows you to replace and build your soil test levels in each field. You can target the optimal nutrient levels and make your fertilizer dollar go further. MFA’s Nutri-Track program is focused on putting nutrients where they are needed and avoiding over-application in areas that won’t perform.

While on the topic of nutrient management, and as we head into another application season, you need to take a step back and think about what practices you adopted on your farm.

The 4Rs promote the best management practices to achieve your yield goals while reducing nutrient loss and increasing nutrient use efficacy. So what are the 4Rs? Right source, right rate, right time, right place.

It’s important as a producer to pay attention to all the above. Not only from an expense standpoint, but from an environment standpoint.

Applying fertilizer while paying attention to the 4Rs will help growers produce more with less land. It will also help you retain nutrients where you intend for them to be—in the field instead of heading downstream.

There are increasing regulatory pressures zeroing in on your farm. Nutrient stewardship is just one of them. Out East, EPA has assigned 44 percent of the nitrogen and phosphorus loads to the Chesapeake Bay to agriculture. If that seems distant enough for comfort, look to the Des Moines Water Works issue. There is legal battling there over field runoff as I write this. Then there is Gulf hypoxia. These issues won’t just go away.

While you may be most interested in the 4Rs as a way to get the most efficient use of inputs, it is also important as a way to demonstrate our commitment to soil stewardship, proper fertilization practices and the economic benefit of using proper fertilization techniques.

I believe that the average non- farmer, the typical consumer, misunderstands the concept of fertilization in commercial agriculture. Hopefully, the 4R program can help dispel misconceptions by the general public. We know it can help you be more efficient.

For more information, please visit or stop by your local store for more information.

Phosphorus trends down

Written by Steve Fairchild on .

This summer when the International Plant Nutrition Institute released its latest soil sample survey, there was a new twist. For the first time, the organization did statistical analysis on long-term soil fertility trends. Looking at data from four million soil samples collected since 2001, IPNI was able to show that crop fields in parts of the Midwest are trending down in phosphorus. Missouri and Kansas were among the states leading in soil test phosphorus decline.

A look at input trends versus crop removal over that period, shows that in some areas cropland is being mined, a practice that will eventually reduce yield or require expensive fertility catch-up programs.

The trick with talking about soil nutrients in a sweeping fashion is that there is high variability in soil fertilities levels on different types of farms in the Midwest. The nearby map, shows the difference that separates Missouri and Kansas from Arkansas and Oklahoma. The kinds of crop grown have a significant effect on how much phosphorus is removed through harvest. Animal production and cycling nutrients back to the land through manure is a factor, too.

According to Dr. Tom Bruulsema, IPNI’s Phosphorous Program director, the soil sample survey revealed that “across North America, the fraction of soils testing below critical for phosphorus decreased from about 60 percent in the 1960s to a low of 40 percent in 2005, but has increased to 44 percent over the past ten years. In key states of the Corn Belt, the depletion trend continues from the mid-1980s. The 56 percent of soils currently above critical represent two levels of legacy.”

“Legacy” phosphorus refers to stores of phosphorus in soil profiles that may exist outside of cropping areas or remain unavailable to the crop. “While it is difficult to define the precise soil test level that separates “too much” from ‘optimum’ legacy, the tools of precision agriculture should equip growers to maintain soil test levels just a little above critical,” reported Bruulsema. “Variable rate technology—applying the ‘right rate’ of phosphorus in the ‘right place’ to match soil and crop need—enables the management of legacy to desirable levels.” He added, “Most soils retain most of any phosphorus applied. The little that leaks, however, can harm the environment. Acute risks of losses accompanying application of fertilizers or manures can be controlled through ‘right time’ and ‘right place.’ Timing applications to avoid periods when risks of runoff are high, and placing them into instead of on top of the soil can make large differences on the amount of phosphorus delivered to the edge of the field. Conservation practices that control soil erosion are also important in controlling losses of particulate forms of the legacy.”

As part of the organization’s continuing effort to educate growers, IPNI has developed an interactive website ( to share data from the soil test survey. This summary shows that soil tests do change over time in response to management. Regular soil sampling can pay its way


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