Crops

Nitrogen models can improve nutrient stewardship

Written by Dr. Jason Weirich on .

What a year we’ve had—from nearly perfect planting conditions to a drought that affected most of our trade territory to more rain during harvest season. Is this the new norm? Maybe.

In most cases, we’ve seen higher yields in corn this year than we expected, but we know that yield variability across fields is normal. We’ve also seen the same when we look at nutrient values. Do they always correspond? Do the high-yielding spots always have the higher nutrient values? The short answer to both of these questions is, “No.” Sometimes the areas with lower nutrient levels might be your highest-yielding spots in the field. This may sound confusing, but these areas are removing more nutrients than others. So it only makes sense that we would put back different rates of fertilizer. Right? This is a common issue we discuss when visiting with producers.

This variability in nutrient values can cause headaches when planning how to replace the P and K that your crop removed. While the flat-rate method of replacing what the whole field averaged has worked in the past, I believe that variable-rate application of nutrients is one of the best management practices that we should all consider to help minimize environmental issues and increase yield. This allows your fertilizer dollar to go further. Nutri-Track programs have a strong focus on nutrient stewardship. We want to put your fertilizer where it will get you the biggest return.

As you may have seen, the first week of October we announced that MFA is partnering with Adapt-N to offer Nutri-Track N recommendations with all of our current Nutri-Track acres (see related story on page 5). This program allows our agronomists and precision specialists to work with producers to employ a nitrogen model to determine optimal rates for your fields. This model takes in a number of factors to determine the right N rate. The tool evaluates organic matter, soil type, rainfall and other variables that affect nitrogen. We then use this model-based N recommendation to have a conversation with you to find efficiencies in nutrient stewardship as well as increasing yield.

Over the past couple of years, two of our producers have been named 4R Advocates, a national award for nutrient stewardship. The 4Rs promote general best management practices that are the foundation of our precision programs: the Right Source, Right Rate, Right Time and Right Place. While this may sound simple, it can also be very complex. The 4R program is important, because it demonstrates our commitment to soil stewardship, proper fertilization practices and the economic benefit of these techniques.

I also feel strongly that the average person, not involved in agriculture, misunderstands the concept of fertilization in commercial farming. The 4R program may help dispel some misconceptions by the general public. For more information, visit www.nutrientstewardship.org or stop by your local MFA.

Do you know your soil?

Written by Jason Worthington, Thad Becker, D.J. Vollrath on .

Fall always brings up conversations about soil management. Typically, when we think of soil considerations, we think about fertility. “How much N, P and K should I apply?” is generally the first question that comes to mind. Soil tests and yield maps are great tools for answering that question. Recommendations for these nutrients and other soil amendments such as lime are critical management aspects and perhaps the most important to address. However, fertility levels are only a portion of the insight growers can access through MFA’s Nutri-Track program.

Understanding physical soil properties and how they fluctuate across a field can provide valuable clues to address fertility management, hybrid and variety selection, planting rates and even weed control concerns. Among key properties are soil texture—the amount of sand, silt and clay in the soil—and organic matter. Both of these soil characteristics can impact drainage, resistance to compaction, nutrient-holding capacity, behavior of residual herbicides and other factors. Soil characteristics even impact the spectrum of weed species in the field because certain soil types are more conducive to certain weeds.

How do we manage not only variable soil fertility but also variable soil properties? There are many solutions for that: variable-rate nitrogen, nitrogen modeling, comparing yield zones to soil zones, variable-rate seeding, multi-hybrid planting or even something as simple as selecting a hybrid well suited for the unique conditions of your field. But, before any of these solutions can be implemented, it is critical to understand which soil properties you have. Traditionally, to do this, we used soil maps developed by the NRCS more than 50 years ago without the level of technology we have today. Now we have innovations such as Veris toolbars that use electrical conductivity (EC) and optical sensors to more accurately identify soil zones. These values relate closely to soil texture and organic matter. The chart in Figure 1 shows examples of how these readings can be used to measure zones and the other insights they can provide.

Just below the chart, the photos of soybeans in Zone 1, left, and Zone 4, right, depict the variability of the soil properties in the field. From these images, it’s clear that the varying soil types and properties greatly impacted the growth and development of the soybean crop, especially in a dry year such as 2018. Beyond the differences in canopy and plant height, there was a significant difference in the number of pods and blooms.  

It’s not surprising that coarser soils with lower water-holding capacities should be more prone to stress, but we did not anticipate the stark difference in weed pressure based on soil type. The coarser soil had a much higher level of weed pressure, likely due to multiple factors such as reduced canopy and differing soil/herbicide interactions.

So now that we know where these soils differ and how nutrients, crops and pests respond differently to these zones, how can we more effectively manage them? Zone 1 might respond better to lower seeding populations, a more defensive corn hybrid and lower cation exchange capacity. Coarser soil texture will not hold on to nitrogen fertilizer as well as soil with higher cation exchange capacity. Zone 4 may facilitate potentially higher-yielding hybrids at higher populations, and it may not be as risky to apply high rates of N to it.

When evaluating plans for next spring, soil fertility is critical, but it is not the only soil property to consider. Advanced EC and organic mapping solutions from MFA’s Nutri-Track program can provide valuable insights and a basis for fertilizer recommendations, seeding information, aerial imagery and even pest scouting reports. It all starts with understanding the underlying soil properties and the extent of how those properties vary across the field.

For more information on EC mapping, contact your MFA precision specialist or Nutri-Track consultant.

Manage diseases with multi-faceted approach

Written by Jason Worthington on .

When selecting a foliar fungicide, producers typically had two choices: triazoles and strobilurins. Before making a decision, you had to weigh the pros and cons of the two chemistry groups.

Time passed, and eventually premixes of the two classes of fungicides became the norm, making those decisions much easier. Two modes of action with a broad spectrum helped fight resistance concerns, extended the effective application window and increased the fungicide’s effectiveness.  

Over the past few years, foliar fungicide choices have been enhanced again with products containing not only strobilurins and triazoles but also the SDHI (succinate dehydrogenase inhibitors) class of chemistry. Examples include Trivapro from Syngenta and Priaxor from BASF. Unlike a strobilurin-triazole combination, adding SDHIs to the mix makes fungicide selection a little more complex. I believe complexity is a more than fair price to pay for added efficacy, but it does mean that you need to consider the options more carefully.

Like strobilurins, SDHI are respiration inhibitors, but they are commonly mischaracterized as having unique modes of action. Rather, they have different “sites of action” affecting mitochondrial respiration that prevents spore germination and mycelial growth in plant pathogens. Because strobilurins and SDHIs share the same mode of action, there is concern that cross resistance will develop between the two fungicide classes. That’s why we recommend using them with an additional mode of action, such as triazoles.

While premixes with SDHIs are fairly new, the SDHIs have been used in specialty crops since the 1970s. However, they’ve had limited uses in row-crop production until recently. Their application in corn, soybeans and wheat has been limited because, as a standalone product, SDHIs are effective against a very narrow range of diseases compared to strobilurins or triazoles.  

So if SDHIs are not a separate mode of action to the strobilurins and have a more limited spectrum of disease control, why adopt them? Depending on the particular active ingredient, benefits of SDHIs include extended residual activity, control beyond that of other active ingredients and synergistic performance with strobilurins. Good examples of additional control from adding an SDHI is extended residual activity against rusts such as stripe rust in wheat and southern rust in corn when using Trivapro. Trivapro is basically Quilt XL, a strobilurin and triazole premix plus Solatenol, an SDHI. Though Solatenol is pretty narrowly focused on rusts, it has a higher efficacy and length of control on that family of diseases than Quilt XL alone.  

Since strobilurins and SDHIs share a mode of action but have different sites of action, they attack mitochondrial respiration and the production of adenosine triphosphate (ATP) in targeted diseases at two spots, creating some synergy. Think of it this way. If ATP production were a road that had to cross several creeks, using both an SDHI and a strobilurin would be like taking out two bridges instead of just one.

With the added benefits that these new three-way fungicide mixes offer, it’s important to understand what diseases you most commonly face to ensure that you get the most out of the product. If the proper SDHI is not matched to your driver disease, the additional benefit won’t be realized. It would be like adding a grass herbicide to help with waterhemp control. It may not hurt control, but it won’t enhance it. Are you in an area where southern rust is a perennial problem, or is northern corn leaf blight or grey leaf spot a bigger issue? What diseases are favored by this year’s weather conditions?

It will be less of a one-size-fits-all approach when selecting fungicides going forward, but, if managed appropriately, the benefits of the additional chemistry bring rewards.

With weed control, do the right thing

Written by Dr. Jason Weirich on .

With all the talk about weed control and the issues surrounding it, I find it fitting to discuss that topic this month. Even with the drop in commodity prices, weeds are still going to emerge and compete with your crop. When it comes to weed control, we can’t afford to give up on doing the right thing.

Herbicide resistance has driven the adoption of residual herbicides in corn and soybeans. Overlapping residual herbicides are still the best weed control practices you can implement on your farm. It might be the only way we can preserve multiple herbicide trait packages.

Let me explain. The overuse of Liberty as a source of weed control makes me believe it’s only a matter of time before we lose the effectiveness of that technology. I know many growers are using overlapping residuals with the Liberty Link system, but we also have growers who are not. This single mode of action on off-label weeds leads us down a road that doesn’t end well for the technology.

When we look at the Roundup Ready system, overlapping residuals are controlling our driver weeds such as waterhemp, Palmer pigweed, marestail, giant ragweed, etc. Yes, we do have issues at times with failure to get that timely rain to activate the residuals, but it is the best option we have.

In the Roundup Ready system, we have seen increased over-the-top applications of the class of herbicides known as PPO (protoporphyrinogen oxidase). With timely applications, we can usually do a good job of cleaning up some of the escaped weeds. But every year, we all can pinpoint that one field that gets hit with everything but the kitchen sink. We have seen a rise in performance issues with these type of products (Cobra, Blazer, Flexstar, etc.) even on labeled weeds. Over-the-top usage of PPO has provided much relief from some of the herbicide resistance issues we have seen, but it appears that is coming to an end, at least for the time being.

Now let’s talk about the Xtend cropping system. By now you are aware of the protocols that MFA has put in place to help steward this program past the 2018 season. I feel that this is the best way to keep this technology for the future. You may ask, “Why past 2018?” When these products received the label for the 2017-18 season, it was good for two years. This season will be pivotal for the future of this technology. I believe that this system can be stewarded, but we must utilize overlapping residual herbicides to make it so. We simply must follow the label and all the guidelines to help protect this technology.

What does that mean? Well, we know that the label restrictions will limit the days in which applications of these products can be made during the season. If the spraying conditions aren’t right, we must stop application or change our weed-control tactics. We have to follow the label, or we could lose the use of this herbicide. This chemistry isn’t a silver bullet, and it shouldn’t be treated like one.

Does your integrated weed management plan consider the use or non-use of dicamba? Does your plan utilize overlapping residuals in all cropping systems? Does your plan have the proper adjuvants and/or drift reduction agents listed? I hope that by the time this reaches your mailbox, you already have that plan in place. If not, please reach out to one of our MFA or affiliated locations to develop yours today.

Lose the loss with nitrogen stabilizers

Written by Dr. Jason Weirich on .

Does this product work? That’s the question I often get about nitrogen stabilizers. There are plenty out there in the marketplace these days. Pick up any farm magazine (including this one), and you’ll see some type of advertisement or article about nitrogen stabilizer. I know this causes a lot of confusion, so allow me to explain more about their purpose and performance.

Nitrogen stewardship is one of the most important things we can do to protect our yield and environment. Nitrogen stabilizers are commonly used to protect against nitrogen losses through volatilization, denitrification and leaching.

It’s important to understand these processes, so I’m going to get technical. Nitrification occurs when ammonium is converted to nitrite in the soil by nitrosomonas bacteria, and then further oxidized to nitrate by nitrobacter bacteria. A majority of the nitrogen taken up by the plant is in the nitrate form, but most plants can also take up ammonium.

Once in the nitrate form, the nitrogen is subject to loss. Nitrate moves freely throughout the soil profile with moisture. In coarse-textured, well-drained soils, nitrate can leach below the root zone and become unavailable to the crop. Nitrate is also subject to denitrification, a biological process that converts nitrate to a gas that is lost to the atmosphere. This occurs in waterlogged soils.

Currently there are two proven nitrification inhibitors on the market: nitrapyrin and dicyandiamide (DCD). Nitrapyrin has been used since the 1960s. It has long been marketed as N-Serve and most recently as Instinct, an encapsulated product for dry and liquid fertilizers. Instinct can also be used in liquid manure. DCD is the nitrification inhibitor in Agrotain Plus and Super U.

Growers often ask me just how long N-Serve protects nitrogen in the soil. A general rule of thumb is 90 days for fall-applied nitrogen. Keep track of those days by counting the date of application until soil temperatures drop below 40 degrees. Resume counting in spring when soil temperatures warm above 40 degrees. In the spring, expect eight weeks of activity from an April 15 nitrogen application, seven weeks from a May 1 application and six weeks from a May 15 application. Research indicates about a 7-percent yield advantage from fall-applied nitrogen and a 5-percent advantage from spring applications.

Another nitrogen loss avenue is volatilization—the loss of free ammonia to the atmosphere. This process has several steps. First, an enzyme (urease) in the soil and organic residue act on urea and convert it to an unstable form, which can quickly change to ammonia and carbon dioxide. With ideal conditions, this unstable form is converted to ammonium and is available for plant take-up.

However, when conditions are less than ideal, the ammonia can be lost into the atmosphere. Factors that influence this process are urease activity, temperature, soil moisture, application method, soil pH and cation exchange capacity, a measure of the soil’s ability to hold positively charged ions.

The greatest potential for loss occurs when there are high amounts of residue on the soil surface and the nitrogen source is applied on top of the field. In MFA’s trade territory, the most common concern I hear from growers is about how much nitrogen they have lost when an application is followed by a week of hot, windy and dry days.

Research shows that the potential for nitrogen losses through ammonia volatilization can be reduced when using a urease inhibitor to slow or delay hydrolysis. Slowing this process gives Mother Nature a chance to provide precipitation that moves urea into the soil. The most effective inhibitor currently available is Agrotain (nBTPT).  

Then the question becomes, “How much nBTPT is getting put on my urea?” A few of the products on the market today state they have nBTPT in the jug.  While that may be true, be sure you find out how many parts per million the product provides on a ton of urea.

Nitrogen loss can be one of the most yield-limiting factors in the field. Keeping nitrogen in the root zone and available for the crop not only provides a return on the investment for the grower but also has a beneficial environmental impact by reducing losses into the water and air. Check with your MFA or AGChoice location for more information on using nitrogen stabilizers this spring.

Magazine

  • Subscriptions
  • Advertising
  • This email address is being protected from spambots. You need JavaScript enabled to view it.

Support

  • This email address is being protected from spambots. You need JavaScript enabled to view it.
  • FAQ
  • Copyright Notice