Crops

Watch for seedling soy disease this year

Written by Steve Fairchild on .

If you see something, say something. That’s the mantra for national security, but it can help in your soybean field, too. The early season disease damage you see in the field this year will have an effect on yield at the end of the season. And the fungus will likely be waiting for the next soybean crop, too.

Soybean seedling disease pressure is most common in cold, wet conditions, which are stressful on plants and give diseases a foothold. Compacted soils and heavy clay also tend to increase chances of fungal disease.

The canary-in-the-coal-mine to watch in spring are low-lying areas and wet spots where seedlings often are first to exhibit disease.

What to watch for:

Pythium seed decay and damping-off. Pythium is the most common fungus causing damping-off in soybean. It is more likely to occur on soybeans that are planted early in the season in colder soils. Infected plants have a rotted appearance and can easily be pulled from the soil.

Phytophthora seedling blight. Phytophthora is a soil-borne fungus that causes seed decay, pre- or post-emergence damping-off and seedling blight of soybeans. It is most common in soybeans planted in warm (greater than 65 degrees) and wet soils. The seedling blight phase may cause yellowing, wilting and death of the plant. It is more likely to occur in low-lying or poorly drained areas.

Rhizoctonia seedling blight. Rhizoctonia is another common soil-inhabiting fungus that can cause seed decay and pre-emergence damping-off of soybean seedlings. Symptoms of rhizoctonia are found on seedlings, young plants and even older plants and consist of localized red to reddish-brown lesions near the soil surface. Infected plants may be stunted or less vigorous than healthy plants, causing uneven stands. Severe infestations and dry weather may cause death of the plant. Like phytophthora, rhizoctonia prefers warmer soils.

Fusarium seedling blight. Fusarium seedling blight is caused by a soil-inhabiting fungus and causes weak or stunted plants and uneven stands. The disease causes a rot of the root system while the aboveground portion of the plants may start to turn yellow. Plants may eventually wilt and die during periods of warm to hot weather. The disease is most severe when the soil is saturated and soil temperature is around 57 degrees at planting, conditions that are not as common this year.

Charcoal rot. Charcoal rot is one of the most common diseases found in soybeans. It typically shows up as a mid- to late-season disease on mature soybeans, but can also occur early in the season on seedlings. Symptoms include reddish-brown discoloration from the soil up the stem that may become dark brown to black as the disease progresses. Plants may die if conditions become hot and dry.

There are several approaches to manage seedling disease. The notes you take this year will help you decide which management techniques will best suit the field the next time it is in soybeans.

Seed selection and seed treatments are the key tools. Obviously, you should select resistant or tolerant seed cultivars. Soybean seed lines have disease ratings for Phytophthora root rot (look for the PRR). Keep records of cultivars grown in order to track PRR races that may be present in the field.

Fungicide seed treatments have become more popular as seed costs increase and crop protection companies fine-tuned the offerings. They consistently provide enough yield benefit to pay for the practice. A Kansas State study showed an average yield increase of 2.5 bushels per acre over an eight year period.

But chemistry is only so powerful. Your crop scouting is important for future success. Seed treatment active ingredients should provide control of the pathogens you’ve noted in the field. And it is worth noting: active ingredients that control Pythium and Phytophthora diseases do not affect Rhizoctonia and Fusarium species. Similarly, fungicides that are active against Rhizoctonia and Fusarium have little effect on oomycetes. The University of Missouri has a useful guide on soybeans that includes photos to help identify diseases. Download it at: http://mfa.ag/Tu2SmCf.

If you have questions about diagnosing or treating soybean seedling disease in your fields or about replant decisions, contact your local MFA agronomist.

Fine-tune in-season nitrogen

Written by Jason Worthington on .

In-season nitrogen applications on corn and wheat have long been a part of Midwestern fertility programs. It is rare that wheat fields don’t receive a topdress application of nitrogen—if not two spring applications.

In-season topdressed nitrogen in corn is increasingly common whether it comes as a planned application or as a rescue application.

The perennial question that growers and applicators ask prior to the in-season topdress is how much nitrogen should be applied. That, of course, is the million-dollar question. If you answer it right, you get maximum yield for the input cost. If you answer it wrong, you either leave yield on the table or waste inputs.

Applying the right amount of in-season nitrogen is going to depend on a multitude of factors including soil organic matter; amount of nitrogen applied pre-plant; amount of nitrogen mineralization in the given year; yield potential of the crop; amount of nitrogen leached; amount of nitrogen denitrified; the previous crop, nitrogen stabilizers used, and more. You can see from that list of variables that the right topdress rate of nitrogen won’t be the same every year. Beyond season-to-season variability, changes in topography and soil type within the same field means the appropriate rate will not necessarily be the same from one end of the field to other.

We now have decades of experience in variable-rate fertilizer application. Through this experience and fine-tuning our abilities to collect yield data and soil test information, we have created very accurate recommendations for nutrients like phosphorus and potassium. Building an accurate variable-rate nitrogen recommendation has been more elusive. Improvements on variable-rate nitrogen are hitting the marketplace, however. Choices growers have right now basically come from one of three categories: machine-mounted crop sensors, aerial imagery or nitrogen models.

Crop sensors

Of variable-rate topdress options available, first to the market were crop sensors mounted to nitrogen application equipment. These on-the-go systems, such as AgLeader’s OptRx, work by reading near-infrared light reflected off of target plants. Dark green plants with sufficient nitrogen absorb more and reflect less light than lighter green plants that need more nitrogen.

For variable-rate topdressing with these systems, the first step is to measure areas of sufficient nitrogen and deficient nitrogen in the field with the sensors by driving over the field.

Once initial measurements are taken and application begins, the sensors continuously read the amount of light reflected. Application rates are calculated and adjusted on the fly by the computer and variable-rate controller on the machine. This process is very convenient due to the fact the applicator doesn’t need a recommendation built beforehand. The recommendation is built on the spot by the need of the plants. On the other hand, that means you won’t know how much nitrogen product is required until after application is completed, which can lead to challenges with product delivery.

Aerial imagery

Using aerial images to determine a variable-rate nitrogen recommendation on a field is similar to the principle behind on-the-go sensors. In this approach, the reflectivity of target plants is acquired by an aerial image to determine the topdress nitrogen rates throughout the field. The information can be measured in several different spectrums, but the theory is the same—crops with adequate nitrogen will be greener than those with inadequate nitrogen. The major difference between aerial and on-the-go measurements is that the aerial images can be turned into nitrogen recommendations before the applicator heads to the field, so the total amount of nitrogen is already known.

MFA is evaluating software that processes high-quality images captured from satellites, airplanes or even a grower’s drone to create in-season nitrogen recommendations. The processing time involved in building the recommendation is the challenge. Timing becomes an issue as well. Aerial images and crop sensors work best when the crop canopy is closed, which ensures reflected light is coming from leaves, not bare soil.

Nitrogen models

Nitrogen models work much differently than sensing technologies. Instead of taking a light reading to determine the nitrogen sufficiency of the crop at a specific point in time, nitrogen models attempt to measure the factors that affect nitrogen availability, loss, and a crop’s yield potential to create a nitrogen recommendation. The variables listed above are entered into the model or measured throughout the season to figure nitrogen loss and mineralization. The model’s goal is to predict nitrogen needs for the remainder of the season. This is advantageous from the standpoint that recommendations can be made with some added accuracy over typical flat-rate recommendations. However, if any information is left out or unaccounted for the accuracy of the nitrogen model will decrease. Where sensing or imaging technologies measure current conditions, models are working off of a lot of calculations and assumptions.

Regardless of the method used to develop more accurate in-season nitrogen recommendations, these new options should excite growers. The goal of variable-rate technology with nitrogen and other nutrients is to make sure the right rate is applied in the right place. This is good stewardship for the environment and leads to increases in agronomic productivity and cost efficiency of your inputs.

Keep tight reins on crop nutrients

Written by Dr. Jason Weirich on .

Nutrient management is a leading topic for farmers and ag retailers. It’s going to stay that way for a while. If you look at what’s going for agricultural industry, you see increasing restrictions and requirements on fertilizer manufacturers and suppliers. If you look at the farm level, you see increasing scrutiny on how we use commercial fertilizers.

A 2012 a study from Purdue found that 40.5 percent of row-crop expenditures were spent on fertilizer. That’s a major part of a crop-year investment. Clearly, to be a good manager fiscally, environmentally and agronomically, you need to prevent as much fertilizer loss as possible.

MFA’s Nutri-Track bases recommendations on soil test and yield removal. The program allows you to apply variable-rate N, P and K based on your yield goals and measured fertility levels across the field. Nutri-Track focuses on putting nutrients where they are needed and avoiding over-application in areas that won’t perform.

While some growers assume this kind of management will reduce overall fertilizer application rates, that’s not the case most of the time.

Yield is never even across a field. But what is the variability in nutrient removal from your fields? We know that corn uses 0.45 pounds of P and 0.25 pounds of K per bushel grain produced. Soybeans use 0.9 pounds of P and 1.5 pounds of K per bushel.

How much difference does it make?

Try this example. You have a corn field that has a 150-bushel-per-acre average yield, but varies throughout the field from 80 to 190 bushels per acre.

If you made nutrient plans on a flat 150-bushel-per-acre removal rate, the areas that yielded 80 bushels per acre would receive an extra 31 pounds of P and 17 pounds of K. The areas that yielded 190 bushels would be short 18 pounds of P and 10 pounds of K.

Or, you have a soybean field with an overall 50-bushel-per-acre average but a range of 20 to 80 bushels per acre. If you use the flat 50-bushels-per-acre removal rate, the parts of the field that yielded 20 bushels would receive an extra 27 pounds of P and 45 pounds of K. Areas that yielded 80 bushels would be short 27 pounds of P and 45 pounds of K.

The trick is getting nutrients in the right place at the right time and in the right amounts.

Keep that nitrogen

The other aspect of making sure we are good stewards of our nutrients is stabilization nitrogen. Most recently, I’ve written about the importance of protecting nitrogen from volatilization losses. However, there other modes of loss. Let’s focus on denitrifiction and leaching.

Ammonium (NH4+) sources in the soil go through a process called nitrification. Ammonium is converted to nitrite (NO2-) by nitrosomonas bacteria, and nitrite is further oxidized to nitrate (NO3-) by nitrobacter bacteria. A majority of the nitrogen taken up by the plant is in the nitrate form, however most plants can also take up ammonium (NH4+). Once in the nitrate (NO3-) form, the nitrogen is subject to leaching and denitrification losses. Nitrate moves freely throughout the soil profile with moisture. In coarse-textured, well-drained soils nitrate can leach below the root zone where they become unavailable to the crop. Nitrate is also subject to denitrification losses. Denitrification is a biological process that converts nitrate to gaseous forms of nitrogen that are lost to the atmosphere. It occurs in soils that become waterlogged.

Currently there are two proven nitrification inhibitors on the market: nitrapyrin and dicyandiamide. 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. The other proven nitrification inhibitor on the market is dicyandiamide (DCD). 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 application until soil temperatures drop below 40º F. Resume counting in spring when soil temperatures warm above 40º F.

For spring nitrogen application, expect 8 weeks of activity from an April 15 application; 7 weeks from a May 1 application and 6 weeks from a May 15 application.

Research indicates about a 7 percent yield advantage from fall-applied and a 5 percent advantage from spring-applied nitrogen.

Not a complete wash

Written by Dr. Jason Weirich on .

I would love to deliver this column with the message that we harvested a bountiful crop at our research site last year. Instead, I have to tell you that our research and training plots got a taste of the same weather challenges and environmental damage that other producers in MFA’s trade territory endured in 2015.

This past year was one for the record books. Our planting crew got the corn in the ground in good shape on April 22. Everything seemed like it was going to be perfect. But we had a lot of moisture at the wrong times.

Over the past few years at our plot location near Boonville, Mo., we’ve had some trouble with lodging. In light of that, we made the decision to delay planting our soybean crop until later in May—even though weather would have allowed us to get it in the ground earlier. You can guess what’s next. Soybean planting at the location went from the planned May target date to planting on June 7. Following planting, the skies stayed dark and full of rain. Beans tried to emerge through standing water. Needless to say, our planting-date study turned into a two-date planting-date study—one on June 7 and one on July 6. Surprisingly, the late-planted soybeans caught up to the early-planted soybeans’ height.

Once the crops were in and up, we had MFA employee training on July 29 and a two-day producer tour on August 6 and 7. About 800 people attend these events to learn about different production practices and new products coming down the pipeline.

If you were able to attend either one, you will recall that the corn was outstanding. I only wish it would have finished that way. On Sept. 10, a severe windstorm blew through the area. It caused severe lodging in our corn plots. Flattened corn, with stalks jumping across plot lines is not a pretty sight for a researcher.

We were able to harvest one of the early-look variety trials by having two people on each side of the combine to make sure we didn’t have any contamination from any of the other hybrids. But as we progressed, the practice looked to be less than safe. Thus, we decided to let our plot cooperator combine the rest of the corn. It would have been great to see results from our studies on nitrogen timing; nitrogen source; phosphorus enhancement products; foliar fertilizer; fungicide timing; and variety trials. But employee safety was top priority.

While the corn ended up flat on the ground, we were very hopeful that the soybeans would continue to stand. Although we had severe water logging and stand issues from the rain earlier in the season, we ended up with several good trials. This was the first year we were able to harvest all of the soybean plots at training camp.

We have been testing biologicals from Monsanto Bio-Ag the past couple years and have reported excellent results. Some of the other trials we have been conducting include seed treatments, seed nutritionals, tank contamination, phosphorus enhancement products, Aspire with Microessentials, and varieties to name a few. While they are not reported here, they will become available.

Although last year wasn’t the year we wanted from a research standpoint, we did the best we could. We join you in looking forward to a better growing season this year.


CLICK HERE for more in the Feb 2016 Issue of Today's Farmer Magazine

Drive and learn

Written by Dr. Jason Weirich on .

One thing you can’t complain about as a farmer is the view. Whether it’s the sun setting over a freshly cut hay meadow or watching a whitetail buck dart across a field when he is spooked from a resting spot, there is a lot of beauty in the rural setting. We can debate just what kind of country scene is the most enjoyable, but I’ll suggest that of all the views on your farm, there is one that provides more useful information than most: the one from your combine cab.

What you see from the combine cab can tell you a lot about the cropping year, the success of your management practices and the success of the products you have used. How you’ve done with weed control, planter setup, and water management decisions are just a few things that you can really verify by paying attention to what your field at harvest is telling you.

Here are some tips for a successful combine ride.

Don’t devote 100 percent of your attention to your yield monitor

It can be easy to jump to conclusions if you are not focusing on the right things. For example, yield monitors are great, but often they become such a strong focal point in the cab that they blind you to other information that can provide real insight. The yield data that can be compiled and used for nutrient-removal recommendations along with other long-term trends is very valuable if looked at objectively. Watching the swings on the monitor from the cab can lead to rash decisions. Make sure your monitor is logging information so it can be analyzed later. Then dim the screen for a couple rounds so you can focus on what’s going on in the field.

Grade your planting job

One of the best ways to do this is to evaluate the consistency of corn ears as they enter the head. Not just consistency from one area of the field to the other, but consistency from one ear to the next. Ideally, every ear would be the same size, but fluctuations in timing of emergence or fluctuations of intra-row spacing can really influence ear-size consistency. After ear consistency, evaluate stalk consistency both in spacing from neighboring stalks and in size compared to neighboring stalks. The cause of a spindly stalk is sometimes obvious from the cab. If spacing is even, the plant probably emerged late. If spacing is uneven, intra-row competition is often to blame.

Grade your weed control

Evaluating how weedy a field is from the cab is a universal practice. But to say, “Boy, that field is a mess!” or, “Man, that field is clean!” is not enough. Try to note not just how severe the weed pressure is, but also how diverse it is. What weed species are present? Paying attention to weed height might give some clues about when they emerged. Also, look at the crop condition around the weeds. Was it late pressure due to a delayed or inadequate crop canopy, or is there something to evaluate in the timing or product selection of the herbicide program?

Look for causes, not just effects

There are hundreds of issues both positive and negative that can be picked up from the cab. There are thousands of variables that may have caused that issue. If there is lodged corn, get out and split some stalks. Are there tunnels from insects? Is stalk rot present? Is this a wet area of the field or a droughty area? Is the soil type the reason for a change in performance, or is the nutrient level? Very often the view from the combine will answer questions. It can also raise more questions. But raising those additional questions can still be a valuable part of finding the right answers to improve your stands and yield.

Take Notes

Finally, what I’ve mentioned above is the kind of information you use when you sit down to discuss a crop plan with your MFA advisor. Write it down so you can have it with you. When you bring your MFA precision representative yield data to analyze the notes you take from the field, these extra notes may be the key to really unlocking the information on that field.

Of all the points in the year, harvest can be one of the most enjoyable. However, to ensure that there are future, better harvests to enjoy, it’s best to take the information your field has to offer and make improvements on the lessons these fields provide. Those lessons and improvements must come from objective observations. Informed decisions are a best management practice!

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