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Updated: 1 hour 39 min ago

Use of dicamba on dicamba-resistant soybean

Wed, 10/28/2020 - 07:58

Most people are aware that EPA approved new labels for the dicamba products used on dicamba-resistant crops.  The following describes major changes in the labels and important restictions.  The labels only describe use on the dicamba-resistant crops, therefore eliminating some of the confusion on earlier labels.

Major changes to dicamba use on DR soybean

  • Must use volatility-reduction agent;
  • Apply before June 30 or up to R1 stage, whichever comes first;
  • Always maintain a 240-ft buffer between last treated row and downwind field edge (roads, mowed grass, tolerant crops can be included in the buffer). The previous label required a 110 ft buffer at 22 oz and a 220 ft buffer at 44 oz.  The 44 oz rate has been eliminated from the label.

General restrictions

  • Apply only one hour after sunrise through two hours before sunset;
  • Apply when wind speed at boom height is between 3 and 10 MPH;
  • Do not apply during temperature inversions;
  • Do not apply product if sensitive crops or certain plants are in an adjacent downwind field;
  • Do not apply if rain is expected in next 48 hours that may result in runoff;
  • Maximum boom height of 24”, maximum ground speed of 15 MPH;
  • Dicamba specific training still required;
  • 57 ft omni-directional buffer required in counties with endangered species (Hardin, several in NE IA).

This list isn't comprehensive, just a quick summary of the label. I assume other products will have similar restrictions. 

Bayer Xtendimax w/VGT label

Category: WeedsTags: dicambaXtendimaxEngeniaAuthor: Bob HartzlerCrop(s): Soybean

VIDEO: Tips for Applying Fertilizer with a Spinner Spreader

Tue, 10/27/2020 - 10:54

Field Agronomist Meaghan Anderson and Program Specialist Ryan Bergman explain some tips to make sure you have the best dry fertilizer application for your operation when using a spinner spreader. This includes some tools recommended tools to keep in the cab, like an SGN sizing tool and a crush tester to check the size and density of dry fertilizer particles, and how to set up your machine for the best application with a specific fertilizer or blend. 

Category: Equipment and MachineryTags: Digital Agdry fertilizerfertilizer applicationspinner spreaderAuthors: Ryan W BergmanMeaghan AndersonVideo: 

Soybean sudden death syndrome and the 2020 derecho

Fri, 10/23/2020 - 12:45

The 2020 derecho left large amounts of downed corn as it swept across Iowa. Farmers faced the challenge of determining the best way to deal with this corn, which in some cases is being left in the field. Most of these fields will be planted to soybean in 2021, which brings up an interesting question – how will all the corn residue, including corn kernels, affect soybean diseases next season?

If there is increased corn residue in the field, the typical concerns about cooler, wetter soils should be considered. Cooler, wetter soils in the spring can lead to root and seedling diseases of soybean (e.g., Fusarium root rot, Pythium root rot). As a sidenote, a lot of corn residue in a field may increase the risk of certain corn diseases if planting corn on corn.

Another soybean disease that may be affected is sudden death syndrome (SDS). Corn has been shown to be an asymptomatic host, which means it can be infected by the fungus that causes SDS, but does not show symptoms. But more concerning, research from 2016 showed that the pathogen that causes SDS, Fusarium virguliforme (Fv), can actually grow on corn residue, especially the kernels (Navi and Yang, 2016). With soybean checkoff funds, the role of corn residue on SDS development was investigated in Iowa, Indiana, Michigan, Wisconsin, and Ontario, Canada from 2016 to 2018. In these studies, we explored the timing of Fv colonization of corn and soybean roots under different tillage and residue management systems. In all years, Fv levels were detected in corn roots from most fields when sampled at multiple times, with greater levels of Fv being detected in 2017. Tillage practices showed inconsistent effects on Fv root colonization and SDS foliar symptoms. Residue management did not alter root colonization of corn or soybean by Fv. In general, plots with corn residue did not differ in SDS development across site-years, although plots with corn residue did have more SDS in one location. This study did not include corn kernels, which in most years are generally not present in corn residue in large amounts as they are this year.

What does this mean for derecho-affected fields for 2021? To begin with the good, we generally did not observe corn residue affecting SDS development in our research. However, if fields have a history of SDS (Figure 1), the extra corn residue, especially with kernels, may increase the risk of SDS a few ways – it may increase the chance of getting the root rot phase of the disease (cooler, wetter soils early in the season) and may increase the amount of disease-causing inoculum in a field if the corn kernels are indeed colonized by Fv. To put this into perspective however, the role of corn residue on SDS risk is minor compared to the field history (did you have SDS in a field before?) or the weather conditions during the 2021 season.

Foliar symptoms of soybean sudden death syndrome. 

Should farmers treat seed next year for SDS if there is more corn residue? Probably not. The possible greater risk of SDS caused by increased corn residue should not change your previous plans regarding SDS – in other words, if you were already going to treat with an “SDS seed treatment”, then do so. If you are on the fence, perhaps this may push you to use an “SDS seed treatment”. Keep in mind, not all the SDS seed treatments are created equally. Check out the seed treatment efficacy chart for last year’s SDS ratings and a recent Crop Protection Network article on efficacy of seed treatments for SDS, again with the support of soybean checkoff. We will be updating the efficacy chart in early 2021 when we start crunching this summer’s data. Stay tuned.

Category: Plant DiseasesTags: sdsderechoresiduefusariumAuthors: Daren MuellerLeonor LeandroAlison RobertsonCrop(s): Soybean

Protect Yourself From Grain Dust This Fall

Fri, 10/23/2020 - 08:44

Farmers should always be mindful of the respiratory hazards and associated health concerns with exposure to dusts and molds during grain harvest and handling. This becomes especially important in a year like 2020 with the derecho windstorm, drought stress, and harvesting overly dry grain creating a higher potential for damaged and broken grain that could have more fines, dust and mold. 

In this interview with Carolyn Sheridan, founder and executive director of Ag Health and Safety Alliance, she discusses what the respiratory hazards and health concerns are when working around dusty and moldy grain, as well as how to protect yourself with respiratory equipment. Also discussed are some common questions like how to know what type of mask you need, what might be a good alternative to N95 masks during the COVID-19 pandemic, what are the recommendations on reusing disposable N95 masks, and how to store respiratory equipment.

Additional resources: 

Category: Grain Handling and StorageTags: derechodroughtdamaged graingraingrain handlingAuthors: Kristina TeBockhorstCarolyn SheriddanCrop(s): CornMinor cropsSoybeanVideo: 

Core Each Grain Bin This Fall

Tue, 10/20/2020 - 12:30

2020 corn harvest in Iowa is likely to include increased amounts of damaged grain from the drought, derecho, or excessively dry corn at harvest. As grain bins are filled, fines and broken or damaged kernels tend to accumulate near the center of the grain pile, while whole and higher quality kernels tend to slide to the outer edges of the pile. This leads to a concentration of low quality and damaged grain in the center core of the bin. Additionally, with the greater depth of grain under the center of the peaked fill, this central core receives less airflow and is at much higher risk for spoiling. Reduce this risk by coring the bin as soon as it is filled.

Coring the bin removes the narrow cylindrical core of grain extending from the grain surface down to the unloading sump. The center peak will be the first grain drawn down through this core to the unloading auger. Unload until half of the grain peak is removed and the grain surface makes a “W” shape. This serves two purposes. First, the center core of grain with the highest concentration of fines and damaged kernels is removed. Second, the grain depth at the center of the bin is now roughly equal to the grain depth at the sidewall, making the overall grain depth more uniform. Both results increase aeration uniformity and reduce the risk of grain spoiling during storage.

The number of bushels removed with half of the peak height to properly core the bin is a function of bin diameter. The bushels to remove when coring is equal to the bin diameter (in feet) cubed, divided by 90. Bushels = (diameter x diameter x diameter) / 90. For a bin with sidewall height roughly equal to diameter, coring bushels equals about 1.5 percent of bin capacity. If sidewall height is only ¾ of bin diameter, coring would remove about 2 percent, and if sidewall height is 1.5 times diameter, coring would remove about 1 percent. Core each of your bins this fall and contact your Extension field Ag engineer for more information.

Category: Grain Handling and StorageTags: corn graingraingrain bingrain storagecoring binAuthors: Shawn ShouseKristina TeBockhorstCrop(s): CornMinor cropsSoybean

Harvesting Excessively Dry Corn

Mon, 10/19/2020 - 12:56

Unusually warm weather in Iowa the second week of October led to rapid in-field drying of crops. Many farmers now find corn at 11 to 14 percent moisture content in the field. Excessively dry corn is more brittle and susceptible to mechanical damage during harvest. Dr. Charles Hurburgh notes that corn breakage potential increases by a factor of 2 for every 2 points of moisture below 16%.

The primary risk of breakage occurs in the threshing cylinder. Because threshing of drier corn is easier, it may be possible to maintain efficient threshing while adjusting settings to be less aggressive. If unacceptable breakage is occurring, try reducing cylinder speed and/or opening concave clearance. Check for complete threshing as you make adjustments. Remember that extra mechanical damage during harvest increases the need for coring bins after they are filled.

One more challenge for 2020. Stay safe. Take care of yourself. We’ll get through this together.

Category: Crop ProductionEquipment and MachineryGrain Handling and StorageTags: droughtcorn harvestharvest issuesAuthor: Shawn ShouseCrop(s): Corn

Early Fall Applied Manure Can Lead to Corn Yield Loss

Wed, 10/14/2020 - 21:00

The early harvest this year has created opportunities to complete fall field work and manure applications much earlier than usual. However, applying manure before soils have cooled to below 50°F can be a costly decision. Pushing manure application to later in the fall or waiting until spring can help to prevent nitrogen loss and better match nutrient availability with nutrient demand by crops.

A research trial at the ISU Northeast Research and Demonstration Farm near Nashua, IA found significant yield reductions when fall manure was applied when soil temperatures exceeded 50°F. In a corn-soybean rotation, late fall applied manure (soils < 50°F) averaged 40 bu/ac greater corn yield than early fall manure over a 3-yr period from 2016 to 2018. Weather conditions in the fall of 2018 prevented the early to late fall manure comparison for 2019. However, in a late fall to spring manure comparison, the spring manure treatment had an 18 bu/ac yield advantage. Similarly, a late fall to spring manure comparison in continuous corn showed a 38 bu/ac yield advantage (3-yr average) for the spring-applied manure. Research conducted at other locations has also reported yield advantages with delaying manure application timing (Table 1).

There is always a possibility of poor weather conditions if manure application is delayed, but this needs to be compared with the risk of nitrogen loss and lower yields when manure is applied too early in the fall. See this ICM Blog for more information, including the effects of a cereal rye cover crop with early-fall applied manure.

Table 1. Corn yield and gross revenue advantage with delayed manure application assuming a corn price of $3.25 per bushel.

Category: Crop ProductionTags: fall manure applicationliquid manure applicationmanuremanure nutrientsnitrogenAuthor: Brian DoughertyCrop(s): Corn

Tips for Handling, Drying, and Storing Damaged Grain

Wed, 10/14/2020 - 09:53

Grain damage from the August 10 derecho storm and drought is widespread in the state and highly variable. The following is a list of five tips or good practices that farmers should consider this fall for good grain management, especially when working with suboptimal quality grain. At the end of the article, you'll find a video that addresses these five tips as well!

Know your grain quality.

  • Information on grain quality factors will be essential to know the level of risk with attempting to store this grain. Molds, test weight, and high variability in quality may be issues.
    • Test weights could be low, as storm damage hindered photosynthesis and grain fill. Low test weight grain will have reduced storability. Test weights near 45 lb/bu will have a severe storage risk and extremely limited market potential; avoid picking this grain up with the combine or letting it enter the tank.
    • Mold growth is a concern in drought stressed and wind damaged grain. Some molds can produce toxins under the right conditions. Mold and toxins should not get worse in storage with proper drying and cooling (dried to 15% or less and cooled immediately), continued monitoring, and aeration.
  • Quality is an insurable factor but needs to be adjusted for by the insurance company before entering into storage, the elevator, or the point of sale.
    • With severely damaged grain, determine if a buyer exists and what the discount is. The buyer will ultimately dictate acceptance and pricing.
    • Ask insurer what quality factors (test weight, damage) and perhaps feed safety factors (mycotoxins) will be considered in their adjustment. Get another (repeat) adjustment if quality changes out in the field.
  • Sample from a representative area just before or at harvest. Grain quality can change under certain weather conditions or with enough time between sampling and harvest.
    • At-harvest tank samples are preferred. Ideally, to get a representative sample of the grain quality, a sample should be collected from a stream of grain, such as from the combine unloading auger into a wagon. Use a PVC pipe sampler or a large canister (a coffee can works well) on a pole/stick to sample all the way through the stream of grain three to four times. Ear samples are not recommended.
    • Tests are usually sufficient at local grain elevators for test weight, moisture content, and perhaps damage. For toxin testing, send to a Federal Grain Inspection Service (FGIS)-licensed grain inspection lab. Be sure you have a large enough sample for the test.


Dry quickly when quality is low.

  • High-temperature drying is recommended over low-temperature or natural air drying when quality is poor and storage life may be greatly reduced. Drying faster will minimize the risk of the grain spoiling before it dries.
  • For high-temperature dryers, use the max drying temp that does not damage the corn to increase energy efficiency and drying speed. Use the higher end of drying temperatures for in-bin dryers as well.
    • If damage from the high-temperature dryer is observed (discoloring, wrinkling, blistering, seed coat damage), the drying temperature may need to be reduced. For damaged corn, a maximum temperature of around 160-degrees may limit additional damage.
  • Dry low-quality corn to 1-2 points less than recommended moisture contents for high quality corn. Avoid drying too far below 15%, as this may increase Broken Corn and Foreign Material (BCFM) content and reduces the pounds of salable material.
  • Dry as soon as possible after harvest and don’t hold the grain wet long.
  • Low-temperature drying should be limited to good quality, 21% MC or drier corn, with at least 1 cfm/bu airflow rate.


Cleaning, coring, and cooling are essential.

  • Keep the poorest quality grain separate from better quality grain; do not blend differing qualities. Manage mixed quality grain based on the worst condition present.
  • Coring bins will be essential to remove light grain, fines, and damaged grain particles that are potentially molded and accumulate in the center core of the bin. Toxins are normally much higher in the fines and core as well.
    • “Core” the bin by removing about half the peak height, making an inverted cone or W-shape on the grain surface. Leveling grain surface will also improve aeration and cooling, helping maintain uniform temperatures and quality.
  • Get grain cooled to below 40 degrees as soon as possible.
    • If outdoor temperatures are still high at harvest, cool the grain in cycles with every 10-15-degree fall in average outdoor temperatures and run the fans during cool, dry nights.
    • Pay attention to the air dewpoint temperature when cooling, as low dew points indicate good conditions for cooling.
    • The time it takes to cool an entire bin depends on the airflow rate per bushel. A large drying fan (1 cfm/bu) will take 15 hours or so, while a smaller aeration fan (0.1 cfm/bu) will take at least 150 hours (close to a week). 


Check grain often and aerate for even temperatures.

  • Check low-quality grain in storage more frequently through the winter, or weekly. Check for any indications of mold growth starting to build up in the grain.
  • Smell the first flush of air through the grain for off-smells or odors (musty or sour). The amount of time for this first flush to exit the grain with a large fan could be less than one minute, so two people may be needed to do this.
  • Use a handheld Carbon Dioxide (CO2) sensor for early detection of grain spoilage; run fans and place sensor in the exhaust air (out of the top of the bin generally).
    • Models run from $50-500, with many good options for $100-150. Consider one with an appropriate operating range that includes cold winter temperatures.
    • When you locate a bin with CO2 concentration above 600 ppm and increasing from week to week, use aeration fans during proper weather conditions. When concentrations rise above 1,500 ppm, the grain should be removed within the next few weeks.
  • Aerate intermittently to keep grain cool (30-40 degrees or less) and temperatures even throughout the bin, and cover fan openings when the fans aren’t running.


Don't count on long term storage.

  • Do not attempt to store low-quality grain more than 3-5 months or past this winter, including grain with low test weight, mold damage, with higher CO2 levels during the storage period, or not stored at sufficiently low MC.
  • Use test weight as an indicator of which grain to sell first or keep.
    • Allowable storage time is definitely reduced in low test weight grain. Test weight below 52 lb/bu may have only about half the allowable storage life of good quality corn grain, based on recent anecdotal findings from years with poor quality grain.
  • Use CO2 readings as a real-time indicator of the storage life remaining for the grain.
  • Aerated storage is preferred over unaerated temporary storage practices such as poly/grain bags or unaerated covered piles. If harvest conditions are favorable, it may be possible to harvest corn dry out of the field. In this case, bags and on-farm piles are less risky, especially if filled fast on cold days to have even and cool temperature grain.

Additional resources:

  1. Iowa Grain Quality Initiative
  2. Iowa State University Extension and Outreach Storm Damage Resources
  3. 2020 Drought and Derecho Impacted Corn-Harvest, Mycotoxin Testing and Storage
  4. Sampling Downed Corn for Damage
  5. Combine Adjustments for Harvesting Lodged Corn
  6. Make Safety Your First Priority When Emptying Grain Bins
Category: Equipment and MachineryGrain Handling and StorageTags: derechodroughtcorn graindamaged graingrain dryinggrain handlinggrain storageAuthors: Shawn ShouseKristina TeBockhorstCharles R HurburghDirk MaierCrop(s): CornVideo: 

Cool Stored Grain Now

Tue, 10/13/2020 - 19:43

Recent warm weather was great for drying crops in the field, but resulted in warm grain going into farm storage. Cool that stored grain as soon as possible to extend storage life. Forecast temperatures for the next several days are favorable for cooling stored grain to around 45 degrees. 

Cool stored grain by running aeration fans any time outdoor air temperatures are 10-15 degrees cooler than the grain. The cooling front will move slowly through the grain in the direction of airflow. The air exiting the grain will stay warm until the cooling front gets there. With a big fan or partially filled bin, if the airflow rate is around one cubic foot per minute per bushel (cfm/bushel), the cooling should take around 15 hours. With a small aeration fan and aeration rate around 0.1 cfm/bushel, cooling will take roughly 150 hours (6 days). As outdoor temperatures decline, repeat cooling cycles until stored grain is at 30-40 degrees. 

Core the bin by removing about 2 percent of the bin capacity, or about half of the peak height, after the bin is filled. This removes the grain with the greatest fines concentration and damage, which poses the greatest storage risk. The resulting more uniform grain depth also creates more uniform aeration. Check stored grain weekly through the fall and winter. Run the aeration fan and smell the first air exiting the grain. A musty or sour smell indicates mold growth in the grain. Use a portable carbon dioxide sensor for even earlier warning of mold or insect activity. Carbon dioxide readings above 600 parts per million indicate potential problems, and above 1,500 indicate trouble. 

Contact your Extension Field Ag Engineer for more advice, check out this podcast for tips for handling, drying, and storing damaged grain, and see this bulletin for detailed advice on managing dry grain in storage.

Category: Grain Handling and StorageTags: grain storageaerationAuthor: Shawn ShouseCrop(s): Corn

VIDEO: Respiratory Protection During Harvest

Sun, 10/11/2020 - 20:54

While the weather is working in our favor this year for grain harvest, the crop is drying down quickly and mold and dust are prolific. Dust and mold cause significant respiratory issues that range in symptoms from minor discomfort to more serious illnesses. Protecting yourself from exposure to respiratory hazards should be a priority anytime but especially when working with grain dust or potential molds. With the significant demand for NIOSH-approved N95 masks this year, many farmers have noted that it is nearly impossible to find their typical respiratory protection for harvest and handling grain.

Carolyn Sheridan, Executive Director and Founder of the Ag Health & Safety Alliance, and Iowa State University Extension and Outreach have several resources available, including a short video (below) to discuss an alternative option to disposable facemasks that is more accessible this year.

Category: Grain Handling and StorageTags: grain harvestgrain handlingrespiratory protectionharvest safetysafetyAuthors: Meaghan AndersonChuck SchwabCrop(s): CornMinor cropsSoybeanVideo: 

CropsTV Transitions Live Meetings to Online Delivery

Thu, 10/08/2020 - 16:58

The Integrated Crop Management (ICM) conference and Crop Advantage Series programs have been mainstays of Extension agronomic programming for many years. It is regretful that because of the COVID pandemic, those programs will NOT be offered this coming December and January. We are offering a new virtual program – CropsTV – to replace the ICM conference and Crop Advantage Series programs for this winter.

CropsTV will launch its inaugural season on December 1, 2020 and at least three new episodes will roll out each week through February 4. The episodes will be broadcast live on Tuesday, Wednesday, and Thursday from 9am to 10am. The live broadcast episodes will be available for viewing on-demand in addition to other presentations offered on-demand only. Look forward to seeing the same relevant agronomic topics as normal, just in this new and exciting format! Each presentation will have CCA CEUs available.

Access all the Live and On-Demand content for a one-time $45 registration fee. Registration will open in November 2020 and will continue throughout the program.

Category: Crop ProductionTags: ICM ConferenceCrop Advantage SeriesCropsTVAuthors: Mark LichtMeaghan AndersonBrent PringnitzCrop(s): CornMinor cropsSoybeanBiomass and ForageCover Crop

How much corn seed has germinated in Derecho damaged fields?

Wed, 10/07/2020 - 13:03

A concern for corn fields damaged by this year's Derecho is how best to manage volunteer corn in 2021. Our recommendation is to rotate to soybean or some other crop if at all possible since additional control options are available (Sept 3,2020 article). There have been questions regarding how much viable corn seed is left in these fields after the abundant germination following the September rain events (Figure 1).

Figure 1. A large volunteer corn population was present in a damaged corn field on Oct. 6.  Field was tilled in late August, a frost damaged the corn on Oct. 3.

To estimate how much corn seed remains in these fields, we visited a field that was determined mechanically unharvestable and had received multiple tillage passes in late August/early September. Several one ft2 samples of soil were removed to a depth of six inches, and the number of intact corn seed determined.  There were more than 1 million seeds per acre in the sampled areas (31 seed/ft2).  Based on emerged plants and rotted seeds found in the sampled areas we estimate the intact seed represent about one third of the seed present in the soil following tillage.

Figure 2.  Intact corn seeds found in one ft2 soil samples.

It is likely that a significant percentage of these corn seed will be lost prior to spring. However, there were large numbers of partial corn ears (~15,000/acre) on the soil surface (Figure 3). It is likely these seeds will overwinter more successfully than the corn seeds within the soil profile, and these ears will be a major contributor to volunteer corn populations next spring. In spite of the large amount of corn germination in damaged fields, volunteer corn will still be a signficant problem in these fields.

Figure 3.  Large numbers of intact ears will replinish the volunteer corn seed bank prior to next springs crop.

Category: WeedsTags: volunteer cornAuthors: Bob HartzlerMeaghan AndersonCrop(s): Corn

Anhydrous Ammonia Application in Dry Soil

Fri, 10/02/2020 - 09:47

It is almost time, but not quite yet, that anhydrous ammonia (NH3) applications could begin (remember 50○F and continued cooling 4-inch soil temperature, and the colder the better). However, some areas of Iowa have dry soils this fall. Can anhydrous ammonia be applied to dry soil? Will it be held in dry soil?

Can anhydrous ammonia be applied to dry soils?

Yes. Dry soil can hold ammonia. Even air dried soil contains some moisture, although quite low. Ammonia dissolves readily in water, but it is held or retained in soil by clay and organic matter. The problem with dry soil and low moisture is that soil moisture is needed to temporarily hold (“go into solution”) the ammonia so it can become attached to clay or organic matter as ammonium. If dry soils are cloddy and do not seal properly, the ammonia can be lost at injection, or seep through the large pores between clods after application. Therefore, proper depth of injection and good soil coverage are a must for application into dry soils. Wing sealers immediately above the outlet port on the knife can help close the knife track, limit the size of the retention zone, and reduce vertical movement of ammonia. Closing disks can reduce ammonia loss by covering up the injection track with soil that traps the ammonia as it moves to the soil surface. Reducing the application rate or narrowing the knife spacing reduces the concentration of ammonia in each injection band.

What happens when anhydrous ammonia is injected into soil?

Several physical and chemical reactions take place: dissolution in water, reaction with soil organic matter and clay, and attachment of resulting ammonium ions on the soil cation exchange complex. These reactions all tend to limit the movement of ammonia, with water having the greatest initial effect. The highest concentration of ammonia is at/near the point of injection, with a tapering of the concentration toward the outer edge of the retention zone. Usually the greatest ammonia concentration is within the first inch or two of the injection point, with the overall retention zone being up to 3-4 inches in radius in most soils. The size and shape of an ammonia retention zone vary depending upon the rate of application, knife spacing, the soil, and soil conditions at injection (soil texture, soil structure, organic matter, and moisture status).

Ammonia moves farther at injection in coarse-textured soils and soils low in moisture. Also, if the injection knife causes sidewall smearing (when soils are wet), then ammonia may preferentially move back up the knife slot. Movement toward the soil surface can also occur for some time after application if the soil dries and the knife track “opens up” as the soil dries (also less soil moisture to retain free ammonia in solution with drying soils). A similar movement within the soil can occur if the soil breaks into clods at application and there are large air voids left in the soil and poor knife track coverage. These conditions can result in greater ammonia concentration toward the soil surface, and greater potential for loss to the atmosphere at or after application.

When ammonia is injected into soil, the initial reaction at the point of release is violent. The ammonia reacts and binds with soil constituents such as organic matter and clays. It reacts with water to form ammonium (NH4+). These reactions help retain ammonia at the injection point. With the high affinity for water, soil moisture is important for limiting the movement of ammonia, but does not ultimately determine retention in soil. After conversion to ammonium, which is a positively charged ion, it is held on the soil exchange complex and does not move with water. Only after conversion to nitrate (NO3–), via the nitrification process, can it be lost from soil by leaching or denitrification.

Chemical and biological reaction of anhydrous ammonia in soil

1) NH3 + H2O = NH4+ + OH–

This is chemical reaction of ammonia with water and causes an initial alkaline pH in the ammonia retention zone (pH can temporarily rise above 9 at the point of highest concentration). It is free ammonia and not ammonium that can be lost from soil at application and is damaging to microorganisms and plant seedlings. As pH goes above 7.3, the equilibrium between ammonium and ammonia results in increased free ammonia (the percentage as ammonia would be 1% at pH 7.3, 10% at pH 8.3, and 50% at pH 9.3).

2) 2NH4+ + 3O2 ⇔ 2NO2– + 2H2O + 4H+

3) 2NO2– + O2 ⇔ 2 NO3–

These two reactions are the steps in the biological nitrification process that occurs with ammonium in soil, and ultimately results in a lowering of pH back to the original pH or lower. Nitrification occurs first at the outer edges of an ammonia band, and progresses inward as the initial effects of ammonia injection decrease and the soil conditions become more conducive to microbial growth. Nitrification rate will slow in dry soil, which increases time for high ammonia concentrations, but will resume quickly when soils rewet.

What about damaging corn next spring?

The potential is usually low for fall-applied ammonia to damage corn seed or seedlings. However, if the soil remains dry (and limits nitrification), the ammonia is injected shallow or there is poor soil structure (ammonia placed near the seed location), or the rate of application is high, then it is possible for ammonia damage to occur. The best cure is to inject deep enough with friable soil coverage to get adequate soil separation between the point of ammonia injection and the depth where corn seed will be planted, or offset ammonia bands from future corn rows. For example, if the injection point is 6 to 8 inches in depth, the outer edge of the ammonia retention zone (which would be low in ammonia concentration) is 4 inches from the point of injection, and seed is planted at a 2-inch depth directly over the ammonia track, then the seed would be outside the applied ammonia band. Shallower injection, greater ammonia movement upward from the injection point, wider knife spacing, or higher rates can lead to ammonia being in the seeding area at rates high enough to cause damage.

Bottom line

Be mindful of what is happening at application, especially if soil conditions are not ideal. If you make an application round in the field, and you can still smell ammonia from that application, then you should make adjustments or wait for better conditions. If the soil is breaking into clods, there isn’t good coverage of the knife track with loose soil, and ammonia is escaping (remember your nose tells you if ammonia is escaping; a white vapor is condensed water vapor, not ammonia which is colorless), then stop and either change the way the equipment is working or is set up, or wait until the soil has better structure or moisture.

Category: Soil FertilityTags: fall fertilizationammonia applicationAuthor: John SawyerCrop(s): Corn

Farmed prairie potholes

Tue, 09/29/2020 - 15:11

Prairie potholes?! What are they? Prairie potholes are low-lying, poorly drained soils that are prone to flooding. The prairie pothole region spans north central Iowa as well as Minnesota, the Dakotas, Montana, and parts of Canada. ISU Biomass is exploring how perennial crops (miscanthus) compare to annual crops (corn and soybeans) when planted in prairie potholes. The goal of the project (year 2) is to see if miscanthus is more profitable and can improve ecosystem services compared to corn and soybeans. Dr. Amy Kaleita of the ISU Agricultural & Biosystems Engineering Department has created a diagram (Figure 1) that shows what questions will be addressed.

Driving along the countryside early in the growing season gives a clear picture of why prairie pothole management needs to change. Corn and soybeans are not considered flood tolerant, so planting them in flood-prone regions often leads to loss of yield and sometimes replanting. An alternative to planting corn and soybeans in potholes would be to plant miscanthus instead. If miscanthus is found to yield better than corn and soybeans in potholes, it could be crucial in saving farmers’ resources, time, and money. Figure 2 shows corn and miscanthus plots side-by-side in a prairie pothole. The miscanthus looks healthy (the tall green crops on the right), and the corn (center of the image) looks unhealthy (very short and yellow in color) or dead.  

Figure 2. Flooded pothole at ISU's Sorenson Farm. Photo credit: Heaton Lab


This project is not only interested in end-of-season yield, but also the environmental issues associated with farmed potholes. Natural potholes offer a variety of services including flood abatement, improved water quality, groundwater recharge, carbon sequestration, and increased biodiversity. On the other hand, farmed prairie potholes (annual vegetation) are often hotspots for nitrous oxide, a potent greenhouse gas, and can result in a loss of ecosystem services. In most cases, ISU Biomass expects miscanthus to yield higher, reduce nitrous oxide emissions, and improve ecosystem services of farmed prairie potholes compared to corn and soybeans.


Be sure to check out past and future blogs as well as ISU Biomass on Facebook, Twitter, and Instagram for updates regarding miscanthus!


Product of ISU Biomass Undergrad Team

Category: Crop ProductionTags: miscanthuspotholesAuthors: Tyler DonovanDanielle M Clark (Wilson)Emily HeatonCrop(s): Biomass and Forage

Tips for Harvesting Downed Corn

Fri, 09/25/2020 - 09:26

Farmers in Iowa are faced with some new challenges this harvest season after the derecho swept through the state in early August. In this video, Ben Covington and Dr. Matt Darr with ISU Agricultural and Biosystems Engineering share their tips for harvesting downed corn this fall, including ways to stay safe as you harvest a difficult crop. 


Iowa Concern Hotline - 1-800-447-1985

County Extension Offices

Category: Crop ProductionTags: Digital Agcombine harvesting tipsharvestderechoAuthors: Ben CovingtonMatt DarrRyan W BergmanCrop(s): CornVideo: 

VIDEO: Livestock Feeding Options for Damaged Grain

Wed, 09/23/2020 - 22:57

Many producers in central and east-central Iowa are facing severely damaged corn fields from the recent August 10th derecho. With poor quality grain not suitable for the general grain market or storage, and fields that are not mechanically harvestable, a producer might consider salvaging some value through livestock feed and forage options.

Field Ag Engineers Kristina TeBockhorst and Brian Dougherty recorded two video podcasts to get some of this information out to producers, which have been posted on the Iowa Grain Quality Initiative Website. The first podcast on grazing and baling wind-damaged corn is available at this link. The second podcast with Garland Dahlke, Assistant Scientist in the Iowa State University Animal Science Department, details silage and dry grain quality and nutritive expectations for damaged corn fields, testing recommendations, and pricing adjustment considerations.

Before making any grain or forage harvest decisions, producers should discuss their options with their crop insurance provider. An additional resource for this podcast is the "Corn Quality Problems Could Mean Opportunity for Cattle Feeders: http://www.iowabeefcenter.org/information/DamagedCorn.pdf.

Category: Crop ProductionTags: derechodamaged corndamaged grainlivestock feedAuthors: Kristina TeBockhorstBrian DoughertyCrop(s): CornBiomass and ForageVideo: 

VIDEO: Livestock Grazing and Baling Options for Wind-Damaged Corn

Wed, 09/23/2020 - 22:46

Many producers in central and east-central Iowa are facing severely damaged corn fields from the recent August 10th derecho. With poor quality grain not suitable for the general grain market or storage, and fields that are not mechanically harvestable, a producer might consider salvaging some value through livestock feed and forage options.

Field Ag Engineers Kristina TeBockhorst and Brian Dougherty recorded two video podcasts to get some of this information out to producers, which have been posted on the Iowa Grain Quality Initiative Website. The first podcast with Russ Euken, Iowa State University Extension and Outreach Beef Specialist, discusses the options of grazing and baling damaged corn fields, including insurance questions, infrastructure needs, sizing grazing strips, and good practices for baling dry forage. The second podcast discusses feeding damaged grain and is available at this link.

Before making any grain or forage harvest decisions, producers should discuss their options with their crop insurance provider. An additional resource for this podcast is the Grazing Down Corn Factsheet: http://www.iowabeefcenter.org/information/GrazingDownCorn.pdf.

Category: Crop ProductionTags: derechofeeding foragesforage for livestockdamaged cornAuthors: Kristina TeBockhorstBrian DoughertyCrop(s): CornBiomass and ForageVideo: 

Tips for Calibrating Your Combine's Yield Monitor

Wed, 09/23/2020 - 15:00

When heading into the field for harvest, it’s important to make sure your monitors, sensors and scales are getting accurate numbers. Taking the time to calibrate your combine yield monitor is the first step in making sure you are using high quality yield data to make decisions in your operation.

Iowa State University’s Digital Ag team provides an online interactive monitor guide with step-by-step instructions for operating your displays. Refer to this tool for directions on how to calibrate your combine’s yield monitor. 

Most yield monitoring systems require a single or multipoint calibration. It’s important to know what type of calibration process your particular yield monitor requires. Refer to the manufacturer’s guidelines to be sure you are meeting or exceeding those requirements. Some manufacturers now offer yield monitors with self-calibrating systems that require little to no input from the operator.

A typical calibration process requires three steps:

  • Harvest a calibration load. 
    • For multi-point calibrations these loads should be between 3,000 to 6,000 lbs. 
    • For single-point calibrations these loads can be larger up to a full grain tank.
  • Weigh the calibration load on a grain cart or truck to get a ground truth weight for the load.
  • Enter the ground truth weight into the yield monitor display

This process is repeated for multi-point calibrations using different crop flow rates.

Is Your Scale Accurate?

No matter the make and model of your yield monitor, a scale system is needed to get a “ground truth” load weight. There are many ways to accomplish this, including using seed buggies with scales, grain carts with scales or truckload scale tickets from an elevator. When collecting ground truth load weights for your yield monitor calibration it is important to verify that the scale system you are using is accurate, or you could be introducing more error into your yield data.

Grain Cart Scale Tip: Most growers verify their grain cart scales against truck load net weights from elevator scale tickets. This is a good practice and an easy way to ensure your grain cart scales are still accurate throughout the season. However, when using your grain cart to calibrate your yield monitor, consider leaving the grain cart half full when collecting ground truth weights. This will ensure the weight range on the grain cart scales is closer to the full cart weight values that you have been verifying against elevator tickets.

Why A Multipoint Calibration Process Matters

Yield monitors calculate yield based on fluctuations in mass flow rate. The yield of any given crop will naturally fluctuate throughout a field due to a host of agronomic factors. This means that even if you drive at a constant speed with the combine, the actual flow rate or through-put of the combine will fluctuate as the yield changes. It’s important to have calibration points for these different flow rate ranges to ensure the yield monitor is accurately calculating yield.

These changes in flow rate can be manually simulated for calibration purposes by driving at different ground speeds through an area of the field with consistent yield. It’s important to drive a consistent ground speed for the entire calibration load. Collect several calibration loads at your normal operating speed (for example, 4 mph), then, capture calibration loads at slower and faster ground speeds (for example 2, 3, and 5 mph). This process will manually fluctuate the flow rate through the combine and ensure that you have multiple points throughout the calibration curve.

Failing to calibrate at multiple flow rates will result in less accurate field totals and spatial distribution of yield on a yield map.

Recalibrate when Crop Moisture Changes

Recalibrating your yield monitor throughout the harvest season when crop conditions change. Changes in grain moisture can affect the accuracy of the calibration, and as your crop continues to dry down later in the season the yield monitor’s sensor will react differently. Yield monitors in corn are particularly sensitive to moisture changes.  Corn that is harvested above 20% moisture will require recalibration every 2.5% change in moisture to maintain yield monitor error of less than 5% (figure 1).

Figure 1:  Corn moisture influence on yield monitor error.

As you go through the season, pay close attention to the mechanical components of the grain handling and yield monitor system. Inspect the sensor periodically for dirt buildup or other debris obstructing it. Regularly check for proper tension on the combine’s clean grain elevator chain, as this is critical in maintaining consistent yield monitor accuracy. If you retention the clean grain elevator chain this will often require a new yield monitor calibration to be completed.

Category: Equipment and MachineryTags: Digital Agcombine harvesting tipsharvestcombine adjustmentsAuthors: Levi PowellMatt DarrRyan W Bergman

VIDEO: Management of Volunteer Corn

Mon, 09/21/2020 - 14:42

August's derecho left many Iowans with unharvestable corn. For operations that left their corn in the field, decisions should be made to reduce the problem of volunteer corn next planting season. 

In this video, Field Agronomist Meaghan Anderson and Weed Specialist Bob Hartzler discuss the unique situation many farmers face with volunteer and options for encouraging germination this fall and reducing the number of volunteer plants you may have to deal with next year. 


Category: WeedsTags: derechoweed managementvolunteer corntillageAuthors: Meaghan AndersonBob HartzlerVideo: 

Crop Protection Network (CPN) Needs Your Input!

Mon, 09/21/2020 - 13:31

Help the CPN determine how to serve you best through this short survey.

The Crop Protection Network (CPN) develops tools to help farmers, ag industry, and researchers with crop protection decisions. The CPN is a partnership of university Extension specialists providing unbiased, research-based information at no cost.

The CPN is conducting a survey to help determine how to best serve agricultural clientele now and in the future. You can help by taking a short survey at: https://iastate.qualtrics.com/jfe/form/SV_1FUAhZZ9YZmDva5

Since 2015, the CPN has developed free extension tools including publications, foliar fungicide efficacy guides, annual disease loss estimates, training for field scouts, and a tool for Certified Crop Adviser’s (CCAs) to earn continuing education units. See cropprotectionnetwork.org to access these resources.

Category: Crop ProductionInsects and MitesPesticide EducationPlant DiseasesWeedsTags: Surveycrop protection networkCornSoybeanmanagementwheatpesticidediseaseWeedsinsect pestsAuthor: Daren MuellerCrop(s): CornMinor cropsSoybean