On Farm Research
As harvest rolls to a close you most likely noticed some field variability or have some questions about how various products or production practices may work on your farm. Every year during the winter, UNL Extension educators share research conducted by your peers-other farmers-in their own fields and often those presentations are very interesting to our clientele.
With the advance of farming technologies, it’s easier than ever for more farmers to conduct research on their own farms. Depending on the study, there may be additional time involved, but overall, the farmers I’ve worked with who have conducted on-farm research say they obtained answers to their questions and the power was knowing it was research based on their own farm.
Last winter the two on-farm research groups in Nebraska combined to form the Nebraska On-Farm Research Network. With help from the Nebraska Corn Growers and Nebraska Corn Board, three State-wide studies were rolled out in addition to other studies that producers wanted to conduct on their own farms. That data is still being collected and analyzed right now and results will be presented this winter.
So as you think about the 2012 season, what are the questions you have? Consider working with your local Extension Educator to design a valid research-based experiment to answer the questions on your farm. To learn more, please check out the CropWatch on-farm research page.
What studies would you like to see our group research on-farm in 2013?
Cover Crops after Harvest
The past few months I’ve received several questions on cover crop options particularly after corn or soybean harvest.
Key highlights from this CropWatch article from 
- Most cover crops need at least 30 days of growth to start being effective and many should have 60 days or more days to provide full benefits.
- Cover crop cocktails should be used as much as possible. The diversity in the mixture builds microbial and physical soil function and reduces the risk of failure.
- Check with your local USDA FSA Office and your crop insurance provider regarding the use of cover crops with your farm programs.
How many of you are planting cover crops this year? Which cover crops are you planting? What reasons did you decide to plant cover crops?
Wheat Planting Resources
This dry fall has raised questions about winter wheat planting…should I plant or delay? How much seed should I drop? My wheat has emerged but
how do I assess my stands?
UNL Extension’s CropWatch newsletter has featured several wheat articles from Bob Klein, UNL Extension Cropping Systems Specialist and other Extension faculty. Since they’re on several different CropWatch release dates, I decided to put all the info. in one place for you. Hope this helps!
Recommendations to Compensate for Delayed Winter Wheat Seeding and Improve Yield Potential
For those who have waited to plant winter wheat, Bob Klein, UNL Extension Cropping Systems Specialist, says to increase wheat seeding rate 10-15 lbs per acre (150,000-225,000 seeds/acre) per week for every week delayed after the seeding rate for our area. Hessian fly free seeding dates range from September 25 for most of our area to September 28 in southern Nuckolls and most of Thayer Co.
For no-till, he recommends automatically increasing seeding rate an additional 50%. So if you’re a dryland no-till producer planting in October, he would recommend seeding 90 lbs to 120 lbs maximum of wheat seed. For irrigated wheat, start at at least 90 lbs/ac and increase 15-20 lbs/acre every week later than suggested seeding date but don’t exceed a maximum of 180 lbs/acre of seed.
Determining the Seeding Rate for Your Winter Wheat
A review of seedling rates vs. yield potential: On the average, there are 22 seeds per head and 5 heads per plant, or 110 seeds per plant. With an average seed size of 15,000 seeds per pound or 900,000 seeds per bushel, a pound of average-sized seed with 80 percent germination and emergence has a yield potential of approximately 1.5 bushels per acre. Seeding 40 lb of seed with a weight of 15,000 seed per pound has a yield potential of 60 bushels per acre.
Seedbed Conditions and Seeding Equipment Affect Timing of Wheat Seeding
Paul Jasa, UNL Extension Engineer says to make sure the drill is running lower in back than normal. Transfer more drill weight to the back of the drill and add extra weight to the drill. This will allow for penetration into dry, hard soil, forcing the seed into the soil and insuring seed-to-soil contact. Also, don’t seed wheat too shallow. When using disc drills, plant at a depth of 2 inches or more.
Additional Resources:
- Fertilizer Options for Dryland Wheat: Is Wait and See a Good Option?
- Grasshopper Management Considerations in Emergent Winter Wheat
- Use of Seed Treatment Fungicides to Improve Wheat
- Guides to Winter Wheat Variety Selection
- How Wheat Seeding Date Affects Yields
- Assessing Winter Wheat Stands and Estimating Yield Potential
Drought Dichotomy
We often say water is the lifeblood of agriculture. In a drought year like this, that truly is the case! A case study showing the impacts of irrigated
agriculture to Nebraska this year can be found here.
Interesting is the dichotomy we’re experiencing in south central Nebraska where irrigated fields that were truly fully irrigated may have some of the best yields producers have experienced while in so many areas of the State-even neighbors a few miles away-are experiencing the worst year they have ever faced.
Dryland yields have been all over the board mostly depending on tillage type. Irrigated yields that were truly fully irrigated have been outstanding. Hybrid Maize predictions for our area had been good all year for fully irrigated corn and it looks like they are even better than the long-term average predictions!
Yet, as I drive around the countryside I can’t help but wonder at how many corn stalks are already being disked under. At a time when we’ve had several fires in our own State of Nebraska…when we have farmers and ranchers suffering trying to find forage for their livestock. We are so blessed to have irrigation here and that buffers our producers from weather extremes. But let’s not forget about the others who are hurting right now! I would ask our producers with irrigated fields to please consider leasing your stalks for grazing or baling them this year to help those in need of forage.
Research from UNL shows that cattle and cornstalks go well together.
Some producers worry about compaction but in a dry year like this, compaction is essentially a non-issue-at least this fall. UNL research from 1996-2011 showed the effects of fall and spring-grazing on subsequent corn and soybean yields. On average, yield of the following soybean crop was increased by about 2 bu/ac with fall-winter grazing, and 1.3 bu/ac with spring grazing, compared with no grazing of corn stalks. Yield of corn as the second crop after grazing was not significantly affected resulting in an average of 1-3 bu/ac yield increase depending on fall or spring grazing. Check out this study and all our resources to help with drought decisions.
An upcoming Webinar called Cornstalk Grazing-Understanding the Values to Cattle Producers and Corn Farmers scheduled for Oct. 2 from 12:30 to 1:10 p.m. will provide additional information. If you are unable to view it, it will be recorded with all our Beef Webinars.
So while irrigation has provided life and good yields to many producers’ crops in the area, let’s not forget about our neighbors who are less fortunate. Please consider leasing your corn stalks or baling them to help others in need of forage for their livestock! You can connect with other producers by checking out the Hay and Forage Hotline at 800-422-6692. This hotline lists hay and forage including cornstalks that is available via sale or donation.
Additional Resource: How much to charge for cornstalk grazing?
Harvest #Soybeans at 13%
In spite of green stems and even leaves on some plants, soybeans are surprisingly drier than what you may think. I’ve been hearing reports of 
soybeans in the 7-10% moisture range already in spite of there also being some “lima beans” along with the low moisture beans at harvest.
Harvesting soybeans at 13% moisture is a combination of skill and maybe some luck. Why is 13% so critical? A standard bushel of soybeans weighs 60 lbs. and is 13% moisture. Often beans are delivered to the buyer at lower moisture than 13%. The difference between actual and desired moisture content will result in lost revenue to the grain producer. Here’s how the loss works based on UNL Extension’s “10 Easy Ways to boost profits up to $20/acre”:
- Since 13 percent of the weight is water, only 87 percent is dry matter. The dry matter in a standard bushel is 52.2 pounds and the remaining 7.8 pounds is water.
- If this bushel of soybeans is kept in an open basket and some moisture is allowed to evaporate, the net weight of beans would decrease. If the dry matter weight remains unchanged at the standard 52.2 pounds, the wet basis weight for any moisture content can be calculated.
- For example, a standard bushel at 13 percent moisture weighs 60 pounds. If the moisture content were reduced to 11 percent (89 percent dry matter), the wet basis weight per bushel of the soybeans would be 52.2 pounds of dry matter divided by .89=58.65 pounds. (1.35 pounds less than the standard 60 lb. weight of beans initially placed in the basket). For each 52.2 pounds of dry matter delivered at 11 percent moisture, you miss an opportunity to sell 1.35 pounds of water.
- It is standard practice for buyers to assume 60 pounds of soybeans constitutes a bushel when soybeans are at or below 13 percent moisture. When the beans are below 13 percent, the difference in water content is made up for by an equal number of pounds (wet basis) of soybeans.
- Assuming a 60 bushel per acre yield and selling price of $8.50 per bushel, the potential extra profit the producer could realize if the beans are harvested at 13 percent moisture instead of 11 percent is $11.48 per acre.
Rapid dry-down and difficulty harvesting green stems and pods are the most common reasons for harvesting at lower than standard moisture. The following practices can help producers maintain quality and expected moisture content.
- Adjust harvest practices. When harvesting tough or green stems, make combine adjustments and operate at slower speeds.
- Begin harvesting at 14 percent moisture. Try harvesting when some of the leaves are still dry on the plant; the beans may be drier than you think. Soybeans are fully mature and have stopped accumulating dry matter when 95 percent of the pods are at their mature tan color.
- Plan planting dates and variety selection to spread out plant maturity and harvest.
- Avoid harvest losses from shattering. Four to five beans on the ground per square foot can add up to one bushel per acre loss. Harvest at a slow pace and make adjustments to the combine to match conditions several times a day as conditions change.
Grubs in Lawns!
The past week walking along the sidewalk to my office in the courthouse, I noticed the lawn browning and just thought “it must be late summer 
patch or brown patch”. One day the custodian came into my office saying, “You’ve got to see this!”.
So we went outside and sure enough, we could roll the turf back like a carpet and there were up to 10 grubs in a small patch the size of a dinner plate in several areas of the lawn! We definitely had a grub problem but no fear as it can be resolved.
If you are seeing brown patches in your turf right now, see if you can roll the turf back like a carpet. If it comes easily with no attached roots, it very well may be a grub problem. See if you can view any grubs present; you may have to dig in the soil a little.
What you can do:
Grubs can be controlled this time of year with Trichlorfon (Dylox) and carbaryl (Sevin). Please read and follow label directions. Watering the products in will increase efficacy and help grass roots begin to re-establish. 
If you had a large patch affected and you’re concerned about it coming back, you can always power-rake to remove the dead material and overseed to re-establish grass in that area.
For more information on different types of grubs, please see the following Blog post by my colleague Elizabeth Killinger.
Latest 2012 #Corn Yield Predictions
2012 Corn Yield Potential Forecast Based on Aug. 27 Hybrid-Maize Simulation: Irrigated corn yield potential is predicted to be 2-8% below long-term average, while dryland yield potential in much of the Corn Belt will be moderately to severely reduced, falling 22-67% below normal. Predictions are assuming no stress during pollination and fully irrigated fields with no equipment, disease, or insect problems.
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Simulations were run for dryland corn in Iowa, Illinois, and South Dakota, and for both irrigated and dryland corn in Nebraska. Simulations were based on the typical planting date, hybrid relative maturity, plant population, and soil properties at each location. Underpinning data used in these simulations are provided in Table 1. To evaluate the impact on potential production at 12 sites across the Corn Belt (Figure 1), we used the Hybrid-Maize model to estimate end-of-season yield potential based on actual weather up to August 27, and historical long-term weather data to complete the season using data from each of the past 30 years. This approach gives a “real-time,” in-season estimate of expected yield potential (the median value shown in Table 1) depending on weather conditions from August 27 until the corn crop reaches maturity.
August 27 projections give a narrower range than our projections based on August 13 simulations, and, at some locations the crop reached blacklayer during the past week (Mead, Concord, O’Neill, and Nashua, Iowa). Projected yield potential since August 13 has not changed by more than 7% across all locations, except for the two locations in west central Illinois (Monmouth) and south central Illinois (Bondville) where predicted dryland yield has increased by 30% due to good rains and cooler weather. It should be noted, however, that if unusually hot, dry weather occurred during pollination at these Illinois locations, such a large yield improvement would not be expected due to reduced seed set. Still, projections of final yield potential are below the long-term average at all sites, under both irrigated and dryland conditions (Table 1).
The bottom line is that 2012 irrigated yields will be moderately lower than the long-term averages (2-8% below normal), while dryland corn yield potential in much of the Corn Belt will be moderately to severely reduced (22-67% below normal). It is important to keep in mind that yields can be even lower at places where both prolonged drought and high temperature stress at pollination have occurred. Also, greater field-scale variability is being observed this year in irrigated fields due to the inability of some irrigation systems to keep up with crop water use demand, problems with pivot irrigation nozzles and uneven watering, and additional stresses from insects and diseases. Such problems can contribute to reduced yields at irrigated sites of more than the 2-8% simulated by the model.There is a modest yield loss (5-8%) for locations in South Dakota (Brookings) and west central and north central Illinois (Monmouth and DeKalb) while a moderate yield loss of 22-28% is predicted for dryland corn in central and northeast Iowa (Gilbert and Nashua). Severe yield loss of 32-67% is projected for dryland corn in south central, eastern, and northeastern Nebraska (Clay Center, Mead, and Concord), northwest Iowa (Sutherland), and south central Illinois (Bondville) (Table 1). In contrast to large loss of yield potential in these dryland systems, the projected losses in yield potential at all irrigated sites are modest at about 2-3% in south central Nebraska (Clay Center, Holdrege), and 7-8% in east and northeast Nebraska (O’Neill, Concord, and Mead) (Table 1). Projected irrigated yield potential since August 13 has increased by about 3% due to cooler weather during the past two weeks.
Patricio Grassini, Research Associate Professor, Agronomy and Horticulture Department
Jenny Rees, UNL Extension Educator
Haishun Yang, Associate Professor, Agronomy and Horticulture Department
Kenneth G Cassman, Professor, Agronomy and Horticulture Department
Earlier Hybrid-Maize Predictions
| Table 1. 2012 In-season yield potential forecasts as of August 17 using UNL Hybrid-Maize Model | |||||||||
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| Location, State | Water Regime | Soil Type¶& Initial Water |
Plant Pop.¶ (ac-1) |
Relative Maturity (days) |
Planting Date¶ | Long-term Yp (bu/ac)‡ |
2012 Forecasted Yp (bu/ac) | ||
| Median | |||||||||
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| Holdrege, NE | Irrigated | Silt loam | 32.4k | 113 | April 27 | 248 |
243 | ||
| Clay Center, NE | Irrigated
Rainfed |
Silt clay loam
100% ASW |
32.4k
24.0k |
113 | April 23
April 23 |
250 146 |
242 98 |
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| Mead, NE | Irrigated
Rainfed |
Silt clay loam
100% ASW |
32.4k
28.0k |
113 | April 30 | 240 160 |
224 53 |
||
| Concord, NE | Irrigated
Rainfed |
Silt loam
100% ASW |
32.4k
29.0k |
104 | May 3 | 235 154 |
218 90 |
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| O’Neill, NE | Irrigated | Sandy loam
100% ASW |
32.4k | 106 | May 3 | 225 |
207 | ||
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| Brookings, SD | Rainfed | Silt clay loam
100% ASW |
30.0k | 98 | May 4 | 120 |
110 | ||
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| Sutherland, IA | Rainfed | Silt clay loam
100% ASW |
31.4k | 99 | May 1 | 168 |
104 | ||
| Gilbert, IA | Rainfed | Loam
100% ASW |
32.4k | 110 | April 26 | 200 |
145 |
||
| Nashua, IA | Rainfed | Loam
100% ASW |
32.4k | 99 | May 1 | 198 |
155 | ||
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| Monmouth, IL | Rainfed | Silt loam
100% ASW |
32.4k | 112 | April 27 | 212 |
189 | ||
| DeKalb, IL | Rainfed | Silt clay loam
100% ASW |
32.4k | 111 | May 1 | 201 |
190 | ||
| Bondville, IL | Rainfed | Silt clay loam
100% ASW |
32.4k | 114 | April 20 | 197 |
134 | ||
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| ¶ Simulations based on dominant soil series, average planting date, and plant population (PP) & relative maturity (RM) of most widespread hybrid at each location (Grassini et al., 2009).
‡ Average (20+ years) simulated yield potential (Yp). |
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Aflatoxin Concerns in #Corn
This article originally appeared in http://cropwatch.unl.edu written by Dr. Tamra Jackson-Ziems, UNL Extension Plant Pathologist.
Drought and high temperatures promote development of the disease Aspergillus ear rot (pictured right). The fungi that cause this disease (most commonly, Aspergillus flavus) can produce aflatoxin. Aflatoxin is one of many chemicals in a group known as mycotoxins that are produced by fungi (molds). Mycotoxins, such as aflatoxin, can be toxic to animal and human consumers and, at certain concentrations, can lead to dockage or rejection of grain at elevators.The unusually high temperatures and drought this summer are having severe impacts on Nebraska corn. In addition to reductions in test weight and overall yield, secondary problems are developing in some corn fields as a result of these conditions.
Corn harvested for grain to this point has been predominantly from fields that sustained substantial drought damage leading to early maturation and plant death. Notable aflatoxin contamination appears to be in a small percentage of southeast Nebraska fields, based on samples submitted to several laboratories in the area.
Mycotoxins are common and can be safely consumed at low concentrations. The concentration of aflatoxin that is considered safe for consumption depends on the age and species of the consumer. An abbreviated summary listing the Action Levels identified by the FDA for aflatoxin is listed in Table below.
Testing for Aflatoxin: Farmers and crop consultants can scout high risk fields for Aspergillus ear rot as an indicator for aflatoxin, but only lab testing of grain samples can accurately identify the concentrations of aflatoxin in the grain. Accurate lab test results for aflatoxin will depend greatly on the quality of the sample that is collected and the laboratory methods used to test it. The test results are only applicable to the sample that is submitted, so it is very important to collect an adequate sample for the best results. Refer to the publication, Sampling and Analyzing Feed for Fungal (Mold) Toxins (Mycotoxins) for recommendations on how to collect and submit a high quality sample for mycotoxin analysis.
Contact and submit samples to a laboratory that is certified by the federal Grain Inspection Service and Grain Inspection, Packers, and Stockyards Administration (GIPSA) for mycotoxin analysis for the most accurate results. A GIPSA website lists laboratories certified to conduct testing in Nebraska. They include
- Lincoln Inspection Service, Inc.;
- Fremont Grain Inspection Department, Inc.;
- Omaha Grain Inspection Service, Inc; and the
- Sioux City Inspection and Weighing service Company.
Some grain elevators and individuals may be using a black light (ultraviolet light) to detect for fluorescence as a method for rapid screening of grain samples. This practice is NOT recommended when making decisions about aflatoxin contamination in loads of grain. The component that produces fluorescence under black light is called kojic acid. Although kojic acid is produced by the same fungus that produces aflatoxin, its presence is not necessarily an indicator of aflatoxin and might lead to false positive results and unnecessary rejection of grain.
High Risk Factors for Aflatoxin Contamination in Corn
- Drought-damaged fields, including rainfed (dryland) fields and non-irrigated pivot corners
- Fields or areas with higher incidence of corn ear-feeding insects, such as the corn ear worm
- Grain damaged before or during harvest or after harvest while in storage
Ear rot diseases and aflatoxin are not evenly distributed across fields or in the grain, so scouting and/or sampling should include a substantial portion, at least several acres. The presence of the fungus in kernels does not always correlate well with the presence of aflatoxin, nor does the absence of visible fungal growth necessarily indicate the absence of aflatoxin.Scouting For Aspergillus Ear Rot
- Open husks to view a large number of ears.
- Look for the presence of dusty yellow-green to olive-green spores, especially on the surface of damaged kernels or ear tips (Figure above).
- Pay special attention to higher risk areas.
Harvest and Storage: If fields have documented Aspergillus ear rot and/or risk of aflatoxin contamination, it is recommended that you harvest and keep grain separate from other grain at less risk, such as irrigated fields. Storage of affected grain is not recommended because ear rot diseases and mycotoxins can continue to accumulate during storage. If storage is necessary, cooling and drying grain to less than 15% moisture within 48 hours of harvest will help to slow fungal growth and aflatoxin production. Grain intended to be stored for longer periods of time should be dried to less than 13% moisture.
Presently, it is too early in the harvest to know the extent of aflatoxin contamination in this year’s corn crop, but at this time only a small percentage appears to be affected.
Resources: For more information, refer to the list of publications below or view this week’s episode of Market Journal.
- Plant Disease Profiles #3: Ear Rot Diseases and Grain Molds, EC1901
- Understanding Fungal (Mold) Toxins (Mycotoxins), G1513
- Sampling and Analyzing Feed for Fungal (Mold) Toxins (Mycotoxins), G1515
- Use of Feed Contaminated with Fungal (Mold) Toxins (Mycotoxins), G1514
- Aspergillus Ear Rot and Aflatoxin Production, Iowa State University Integrated Crop Management News
- Check Cornfields for Aspergillus Ear Rot, University of Illinois the Bulletin
| Table 1: FDA action levels for aflatoxin contamination in corn intended for livestock. | |
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| Commodity Action Level | (ppb) |
| Finishing (feedlot) beef cattle | 300 |
| Finishing swine of 100 pounds or greater | 200 |
| Breeding beef cattle, breeding swine, or mature poultry | 100 |
| Immature animals and dairy cattle | 20 |
| For animal species or uses not otherwise specified, or when the intended use is not known | 20 |
| Human food | 20 |
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| Source: FDA Action Levels for Aflatoxin | |
More on Last #Irrigation
It’s been a long irrigation season thus far, but we are so thankful for irrigation in this part of the Country during this drought of 2012! Questions continue to roll in regarding last irrigation for corn and soybeans. Corn at 1/2 starch only needs 2.25″ to finish up so it’s important to know what your soil moisture status is. For most irrigated producers, at 1/2 starch, you should be finished irrigating.
For soybeans at R5 or beginning seed fill, you still need about 6.5″ to finish out the crop. At R6 when the seeds are filling, that drops to 3.5″. At R7 when you begin to see leaves yellowing, that is beginning maturity and you are finished irrigating. They key is we don’t want to fill the profile going into the fall as we’d like to replenish the profile with fall and spring rains and winter snow. However, with soybeans, it’s also critical not to stop irrigating too soon during seed fill.
Gary Zoubek, Extension Educator in York County sheds more light in the following video produced by UNL’s Market Journal.
Latest 2012 #Corn Yield Predictions
The 2012 corn growing season has been unusually hot and dry. To evaluate the impact on potential production at 12 sites across the Corn Belt, we used the Hybrid-Maize model to estimate end-of-season yield potential based on actual weather up to August 13 and historical long-term weather data thereafter. (Data from each of the past 30 years was used.) This approach gives a “real-time,” in-season estimate of expected yield potential (the median value shown inTable 1), and the most probable range (25th to 75th percentiles) depending on weather conditions from August 13 until the corn crop reaches maturity.
By comparing this range of possible simulated end-of-season yield potential against the long-term average (long-term Yp, fourth column from right in Table 1), it is possible to estimate the likelihood for below-average (25th percentile), average (median), or above-average (75th percentile) yields. Comparing estimated 2012 yield potential versus the long-term average gives the size of the expected yield difference. While the 25th percentile projection is most likely if weather conditions are harsher than normal from August 13 until crop maturity, the 75th percentile scenario is more likely if weather is more favorable than is typical at a given site. There is roughly a 50% probability that final yield potential will fall between the 25th and 75th percentile levels, a 75% chance that yield will be at or below the 75th percentile, and a 25% probability that it will be at or below the 25th percentile value.
Simulations were run for dryland corn in Iowa, Illinois, and South Dakota, and for both irrigated and dryland corn in Nebraska. Simulations were based on the typical planting date, hybrid relative maturity, plant population, and soil properties at each location. Underpinning data used in these simulations are provided in Table 1. Details about the Hybrid-Maize model and our simulation forecast methods can be found in a previous CropWatch article.
As the season progresses, the range of yield outcomes shrinks and the 25th and 75th percentile values converge toward the median value. Indeed, August 13 projections give a much narrower range than our projections two weeks earlier based on July 30 simulations. The good news is that projected yield potential since July 30 has stabilized or even increased slightly at 7 of 12 sites as weather has improved, especially during the most recent week. The bad news is that projections of final yield potential are below the long-term average at all but two sites.
Dryland Corn
Even in hot, dry years like 2012, parts of the Corn Belt escape untouched and catch adequate rainfall. This appears to be the case in the northern tier of the Corn Belt (e.g. Brookings, South Dakota) and near the Great Lakes (e.g. Dekalb, Illinois) where projected dryland yield potential is within 2% of the long-term average. In contrast, there is moderate yield loss of 26-33% for dryland corn in south central Nebraska (Clay Center), central and northeast Iowa (Gilbert and Nashua), and west central Illinois (Monmouth). Severe yield loss of 40-65% is projected for dryland corn in eastern and northeastern Nebraska (Mead, Concord), northwest Iowa (Sutherland), and south central Illinois (Bondville).
Irrigated Corn
In contrast to large loss of yield potential in these dryland systems, drought years like 2012 highlight the value of irrigated agriculture and the stability it provides to our food system. Although hotter than average temperatures have shortened the grain filling period at all irrigated sites, which reduces yield potential somewhat, projected decreases are modest at about 5% in south central Nebraska (Clay Center, Holdrege), and 10% in east and northeast Nebraska (O’Neill, Concord, Mead). High grain prices are likely to offset the impact such losses will have on profits from irrigated corn.
Model Reliability
Given the severity of reductions in yield potential at some locations, and the apparent lack of negative impact at others, the question arises as to how reliable these projections are? In areas with relatively little heat or water stress, past experience indicates that predictions of yield potential using Hybrid-Maize are robust. In contrast, we would expect predictions of yield loss to be underestimated by Hybrid-Maize in areas where there was high temperature stress during the critical two to three day period of pollination, or where there were large water deficits that severely reduced development of the leaf canopy before tasseling. Both phenomena are not well accounted for in the current version of the model although we plan to release an improved version of Hybrid-Maize later this year that addresses these deficiencies.
Summary
The bottom line is that 2012 will be a difficult year in terms of U.S. corn production. Although irrigated yields will be somewhat lower than long-term averages, dryland corn yield potential in much of the Corn Belt will be moderately (25-33% below normal) to severely reduced (40-65% below normal). Where both prolonged drought and high temperature stress at pollination occurred, yields could be reduced by 65% or more. The final outcome will be determined by weather conditions until maturity. Fortunately, predicted weather patterns indicate a trend toward more normal temperatures and rainfall in many places.
While 2012 will certainly be a significant drought year, episodic droughts of this magnitude have occurred at regular intervals in the U.S. Corn Belt over the past 100 years of recorded weather data. Nebraska is fortunate that about 70% of total corn production comes from irrigated systems, and that improved agronomic management practices such as conservation tillage and more stress-tolerant hybrids can significantly reduce dryland corn yield losses under moderate drought. But there is little that can be done to mitigate the impact of severe, prolonged drought especially when coupled with high temperature stress at critical growth periods.
Patricio Grassini, Research Associate Professor, Department of Agronomy and Horticulture
Jenny Rees, UNL Extension Educator
Haishun Yang, Associate Professor, Department of Agronomy and Horticulture
Kenneth G Cassman, Professor, Department of Agronomy and Horticulture
| Table 1. 2012 In-season yield potential forecasts as of August 13 using UNL Hybrid-Maize Model | ||||||||
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| Location, State |
Water Regime |
PP¶(ac-1) |
RM¶ (days) |
Planting Date¶ |
Long-term |
2012 Forecasted Yp (bu/ac) |
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|
75th* |
Median |
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| Holdrege, NE |
Irrigated |
32.4k |
113 |
April 27 |
248 |
239 |
232 |
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| Clay Center, NE |
Irrigated |
32.4k |
113 |
April 23 |
250 |
241 |
237 |
|
| Mead, NE |
Irrigated |
32.4k |
113 |
April 30 |
240 |
221 |
216 |
|
| Concord, NE |
Irrigated |
32.4k |
104 |
May 3 |
235 |
210 |
208 |
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| O’Neill, NE |
Irrigated |
32.4k |
106 |
May 3 |
225 |
212 |
203 |
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| Brookings, SD |
Rainfed |
30.0k |
98 |
May 4 |
120 |
127 |
118 |
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| Sutherland, IA |
Rainfed |
31.4k |
99 |
May 1 |
168 |
110 |
99 |
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| Gilbert, IA |
Rainfed |
32.4k |
110 |
April 26 |
200 |
157 |
144 |
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| Nashua, IA |
Rainfed |
32.4k |
99 |
May 1 |
198 |
152 |
147 |
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| Monmouth, IL |
Rainfed |
32.4k |
112 |
April 27 |
212 |
161 |
143 |
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| DeKalb, IL |
Rainfed |
32.4k |
111 |
May 1 |
201 |
227 |
204 |
|
| Bondville, IL |
Rainfed |
32.4k |
114 |
April 20 |
197 |
110 |
105 |
|
|
|
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| ¶ Simulations based on dominant soil series, average planting date, and plant population (PP) and relative maturity (RM) of most widespread hybrid at each location (Grassini et al., 2009). ‡ Average (20+ years) simulated yield potential (Yp). * 75th percentile yields, which represent favorable and unfavorable weather scenarios for the rest of the season. |
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JenResources 