Friday, August 30, 2019

Yield and Quality of July Planted Corn

The Kernels
  • Corn has two peaks in forage quality: one at pollination and one at 50% kernel milkline.
  • Bareness generally reduces yield and grain content resulting in increased fiber content, but this is often accompanied by lower lignin production that increases fiber digestibility. Also, the forage has higher sugar content, and higher crude protein than normal corn silage.
  • Relatively small changes (5 to 8% decrease) in forage quality (Milk per ton) occurs with July planting dates compared to corn planted April 28 to June 1.
  • Milk per acre of July planting dates decreased 17 to 92% to levels ranging from 2,300 to 24,000 lbs milk/ A. 

Record high prevent plant acreage occurred in 2019. In July, many acres were planted to cover crops, including corn (Figure 1). Due to low forage inventories, USDA-RMA allowed cover crop acres to be harvested for silage.

Figure 1. Prevent plant acreage in 2019. Data source: Farm Bureau and USDA-FSA.

Corn has two peaks in forage quality: one at pollination and one at 50% kernel milkline. Forage quality as measured by Milk per Ton is high during vegetative phases prior to flowering. Like all forages, quality decreases after flowering. Unlike other forages, quality improves beginning around R3. The early peak in forage quality at pollination is high in quality but too wet for ensiling. The later peak is more familiar and is the one we typically manage for when producing corn silage because it maximizes both biomass yield and quality.

If pollination is unsuccessful, the forage quality following the first peak does not change and will continue to remain high due to higher sugar content (water soluble carbohydrates), higher crude protein, higher crude fiber and more digestible fiber than normal corn silage. Unsuccessful pollination (bareness) generally reduces yield and grain content resulting in increased fiber content, but this is often accompanied by lower lignin production that increases fiber digestibility.
If pollination is poor yet some kernels are developing, the plant can gain dry matter and farmers should wait with harvest.

Harvesting and Handling Barren Corn
The harvesting challenge is that green, barren stalks will contain 75-90% water. Barren corn is difficult to harvest because it is rank and too wet for silage storage structures. Arlington UW-ARS staff have had some success using a discbine to cut barren corn into a windrow. The windrow would need to dry to desiccate the forage. A forage chopper with a hay pickup attachment is then used to gather and chop the windrow into a wagon for transport to a storage structure for ensiling.

Grazing is an option but be careful about nitrate toxicity problems. If grazing, consider potential for nitrate toxicity. This is especially likely to be a problem if growth was reduced to less than 50% of normal and/or high levels of nitrogen were applied.

If the decision is made to harvest the crop for ensiling, the main consideration will be proper moisture for storage and fermentation. The crop will look drier than it really is, so moisture testing will be critical. Be sure to test whole-plant moisture of chopped corn to assure yourself that acceptable fermentation will occur.

Forage quality of barren and poorly pollinated corn
Coors et al. (1997) evaluated the forage quality of corn with 0, 50 and 100% pollination of the kernels on an ear during 1992 and 1993. These plots were harvested in September.

A typical response of corn to stress is to reduce grain yield. Bareness reduced whole-plant yield by 19% (Table 1). Kernels on ears of 50% ear fill treatments were larger and tended to more than make up for reduced numbers (Albrecht, personal communication). With the exception of protein, as ear fill increased, whole-plant forage quality increased.


Table 1. Forage yield and quality of corn with differing amounts of pollination (n= 24; 1992 and 1993).

Yield and Quality of July Planted Corn
We conducted experiments during 2005 and 2006 to determine what could be expected by planting corn in July. Three corn hybrids (brown midrib, full-, and shorter-season) were planted on five different dates from April 28 to August 1 at Arlington, WI. The 2005 growing season had a killing frost on October 26, which was three weeks later than normal.

Seasonal dry matter production after planting during July ranged from 0.7 to 7.5 Tons DM/A while the same hybrids planted April 28 to June 1 produced 8.7 to 10.0T DM/A (Table 2). Milk per acre is significantly lowered 92 to 17% to levels ranging from 2,300 to 24,000 lbs milk/ A for planting dates in July. Crude protein, NDF and NDFD increased with later planting dates. Although, little starch content was measured in later planting dates, overall milk per Ton tended to decrease slightly. Thus, relatively small changes in Milk per ton occurred during planting dates in July with levels ranging from 2800 to 3200 lbs milk/T, which was a 5 to 8% decrease from corn planted April 28 to June 1.

 Table 2. Corn forage yield and quality response to July planting dates.

Corn can produce significant dry matter yield when planted during July, but the amount produced depends upon when a killing frost occurs. Growers need to check on options available from their insurance companies before taking action and planting corn in late June and July for emergency forage. Herbicide labels must be adhered to before switching to other crops.

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Thursday, August 29, 2019

The “Normal” Pattern of Corn Forage and Grain Development

The Kernels
  • Corn exhibits a “double peak” for corn silage quality during its life cycle with the first NDFD peak at R1 and the second starch content peak at R5.5.
  • Corn as a forage crop reaches maximum yield and quality values at nearly the same time (R5.5).
  • At harvest (R5.5), the wettest plant part is the lower stalk, while the driest plant part is the grain. Adjusting the cutter bar can change forage moisture 3 to 4% points to better target the recommended moisture for the storage structure.

Corn is a high yielding, high energy, low protein forage commonly used for growing and finishing beef cattle, in cow-calf production systems, for growing dairy heifers, and for lactating dairy cows. Corn grown as a forage and fermented in a storage structure preserves the silage for subsequent feed-out. Understanding yield and quality changes during the life cycle of corn is critical for timing harvest of a field.

The “Double Peak” of Corn Silage Quality
Corn exhibits a “double peak” for corn silage quality during its life cycle (Figure 1). The first peak is related to energy derived from stover fiber (NDFD) and water-soluble carbohydrates, while the second peak is derived from NDFD and starch content of grain. Forage quality as measured by Milk per Ton is at the first quality peak just prior to silking (R1). Like all forages, Milk per Ton decreases following flowering (VT-R1). Unlike other forages, corn silage Milk per Ton after the kernel blister stage (R2), steadily increases to a maximum second quality peak around 50% kernel milkline development (R5.5) due to grain yield development.

Forage yield and Milk per Acre

One of the unique aspects of corn as a forage crop is that yield and quality reach maximum values at nearly the same time. Forage yield increases steadily through its life cycle. At R1 all the plant photosynthetic “machinery” is produced on the plant. For most hybrids grown commercially in Wisconsin the grain filling period (R1-R6) is about 55-60 d. Following pollination, grain develops in a sigmoidal fashion with a 7-10 d lag period, followed by a 40-44 d linear phase, and ending with a 7-10 d maturation phase. Starch content increases as grain develops and matures.

Multiplying corn forage yield by Milk per Ton results in Milk per Acre. Milk per acre peaks at R5.5. Then due to leaf senescence and loss, yield and quality tends to decrease slightly.

Using Forage and Grain Moisture for Harvesting
At some point forage yield is no longer as important as timing harvest at the correct moisture for the storage structure to ensure proper fermentation and preservation. The wettest plant part on corn is the lower stalk, which is also of poor quality (low NDFD) and is high in nitrates. The driest plant part is grain. By raising the chopper cutter bar 12 inches, forage moisture decreases 3-4% points. Also, the wettest, poorest quality plant part is left in the field. Forage yield is decreased about 10 to 15%, but forage quality increases 8 to 12%, so that overall Milk per acre is only reduced about 3 to 4%.

The effect on forage moisture is significant when the field is scheduled to be harvested by a custom chopper. By adjusting cutting height, the operator can better achieve the optimum moisture for the storage structure. About a one week shift in harvest timing can be achieved (assuming 0.5% per day drydown rate).



Figure 1. Normal Pattern of Corn Forage and Grain Development in Wisconsin.

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Wednesday, August 28, 2019

Corn Plant Population: The second most important management decision for moving off the yield curve

The Kernels:
  • Farmers are increasing plant densities (PD) in commercial fields. 
  • The economic optimum plant density (EOPD) is lower than the plant density required to maximize grain or forage yield (MYPD). 
  • The economic optimum plant density is likely different between farms and fields within farms.
  • To move off current yield levels, begin by planting a field to what you think is the optimum plant density and at two or three places (rounds) in the field, increase plant population by 10%.

Farmers are increasing plant densities (PD) in commercial fields (Figure 1).  In research plots, the plant density that maximizes corn grain and silage yield has been increasing through time. The economic optimum plant density (EOPD) is a function of corn yield and quality responses, seed cost, and grain or silage price. The economic plant density is lower than the plant density that maximizes yield (MYPD).


Figure 1. Corn plant density of farmer fields since 1982. Data source: USDA-NASS.

Farmers have many questions including: What is the maximum yield PD (MYPD)? What is the economic optimum PD (EOPD)? Is the MYPD and EOPD the same for silage and grain? Do hybrids differ for MYPD and EOPD? Do fields differ for MYPD and EOPD? How does yield risk change with increasing plant density? How does drought affect MYPD and EOPD? Is lodging and barrenness affected by plant density? How should variable rate technology in precision farming systems be adjusted in-field?

Since 1997, plots have been that are 8 rows wide by 25 feet long. Four rows are harvested for silage and the remaining 4 rows are harvested later for grain. The target plant densities have varied by year and ranged from 14 000 to 56 000 plants/A. Adapted, high-performing hybrids were selected using results from the UW Corn Trials and varied for relative maturity (full- and shorter-season). Milk per Ton and Milk per Acre were estimated using Milk2006. The treatment (hybrid x plant density) mean that maximized the measure within a year was set to 100%. The results in Figure 2 were summarize the relationship between various measures and plant density across all experiments conducted between 2008 to 2017.

Maximum grain yield was measured at 41 000 plants/A. The relationship increased to a maximum and then decreased as plant density changed. In agronomic research, it is very difficult to measure grain yield differences less than 5%. So, grain yields within 5% of the maximum grain yield were measured at plant density above 30 000 plants/A. The economic optimum plant density (EOPD) was 35 000 plants/A. The EOPD was within 95% of the maximum at 26 000 plants/A.

Maximum forage yield was measured at 48 000 plants/A and was within 5% of the maximum when plant densities were above 35 000 plants/A. Forage quality as measured by Milk per Ton decreased linearly from a maximum at 18 000 plants/A, but was within 5% of the maximum across the range of plant densities measured. Maximum Milk per Acre was measured at 45 000 plants/A and was within 5% of the maximum at 32 000 plants/A. These results are a good example of the trade-off that exists between forage yield and quality, i.e. the plant density that maximizes Milk per Acre is intermediate between plant densities that maximize forage yield and Milk per Ton.

Plant densities that maximize grain and forage yield are higher than currently recommended plant densities. These results indicate that the plant density that maximizes forage production is about 7000 plants/A higher than the plant density for maximizing grain yield. The economic optimum plant density is lower than the plant density required to maximize grain or forage yield. The economic optimum plant density is likely different between farms and fields within farms.


Figure 2. Relationship between corn plant density and grain yield, economic optimum (AGI), forage yield, Milk/Ton, and Milk/Acre. Data source: Lauer (Arlington 2008-2017).

Adjusting plant density is probably one of the best ways to move off current yield levels. Begin by planting a field to what you think is the optimum plant density and at two or three places (rounds) in the field, increase your population by 10%. For example, if you currently plant at 30 000 plants/A, do so for the majority of your field, but in two or three rounds increase the population to 33 000 plants/A. Measure yield at the end of the season and during the season watch for "runt" plants, tillering, prolific versus ear bareness on plants, big versus small ears, ear tip "nose-back" and plant lodging. Adjust the field accordingly the following year.

Tuesday, August 27, 2019

A “Post-Mortem” of the 2019 Planting Season and What We Can Do About It

The Kernels:
  • The 2019 planting season was “unprecedented.”
  • Harvest season will be extended this year. Corn maturity is all over the board due to late planting, and within field variability is equally as great.
  • Dairy farmers will have to work closely with their custom choppers and let them know when the field was planted, when it silked, the current stage of development, and what the moisture is. 
  • Note silking dates to project calendar days to when a field will mature. Note order that fields silk to plan the harvest queue. It will take approximately 42 to 47 days to get to 50% kernel milk, and 55 to 60 days to get to black layer.

Who can forget the “Drought of 1988” or the “Father’s Day Frost of 1992” or the “Flood of 2008.” The 2019 corn planting season in Wisconsin will have a similar notoriety and be remembered for a long time. Corn planting progress records have been kept by USDA since the 1979 growing season. The 2019 planting season was “unprecedented.”

Farmers in Wisconsin typically plant about 50% of the corn acreage by May 7 (Figure 1). The earliest we have hit the 50% planted acreage level was during 2010 by Week 16. Other early years were 2016, 2006, 2005, 2000, and 1999. The slowest we have hit the 50% mark was 1996 and 2014 at Week 20. That is until 2019 when we hit the 50% mark at Week 21 and what subsequently happened during June. Significant corn acres were planted in July this year. Planting date sets up your season. If you are delayed or planting is extended then workload is delayed or extended as well. Some corn will not make grain or be too expensive to dry. Some corn will not make good corn silage due to lack of grain development prior to a killing frost.

Figure 1. Wisconsin Corn Planting Progress. The average consists of data from 1979 to 2018. Years shown are + 1 standard deviation from the average. Data derived from USDA-NASS.
Corn as a Cover Crop

Who would have thought that corn could be grown as a cover crop? Yet, due to low forage inventories and the relaxing of USDA-RMA rules, corn was allowed as a cover crop to be harvested as an emergency forage. To be sure,  corn is deep-rooted and by the end of the growing season can produce significant residue even when planted in July. A number of management guidelines needed to be considered to qualify including: increased plant population, narrower row spacing, crop rotation, planting into residue, lower nitrogen rate, and good weed control.

Will the Corn Crop Make It?

Corn maturity is all over the board due to late planting, and within field variability is equally as great. An early frost could spell doom for a lot of cornfields. Most late-planted corn will likely be immature and killed by frost. Patience will be required to allow the corn to dry to the proper moisture for storage and preservation. Starch content will be most affected with late-planted corn. However, this can be easily remedied by adding more grain corn into the ration.

Filling bunker and pile silos may also be a challenge where all the corn won’t be ready at the same time. Decisions will need to be made as to whether to start a new pile or risk reopening up an existing pile. Some may choose to just fill a bag with any late-cut corn.

None of this will make life easy for custom chopping operations either. Harvest season will be extended this year, and any information that can be passed along to custom operators will help with planning and proper timing of silage harvest.

In-season Guidelines for Predicting Corn Silage Harvest Date
  1. Note hybrid maturity and planting date of fields intended for silage.
  2. Note tasseling (silking) date. Kernels will be at 50% kernel milk (R5.5) about 42 to 47 days after silking.
  3. After milkline moves, use kernel milk triggers to time corn silage harvest. Use a drydown rate of 0.5% per day to predict date when field will be ready for the storage structure. See http://fyi.uwex.edu/silagedrydown/
  4. Do final check prior to chopping. Adjust cutter height if forage needs are adequate. Raising cutter bar 1 foot, lowers silage moisture 2 to 4 points.
Once corn silks it takes about 55 to 60 days to achieve maturity (R6). Development during grain filling is influenced by temperature, but not as much as during the vegetative leaf emergence stages. Instead the number of days between pollination and a killing frost influence the time to maturity. So, if an average killing frost occurs October 1, then subtracting 55 to 60 days means that the crop must be silking by August 2-7. Silage harvest usually begins around 50% kernel milk which is 42 to 47 days after silking, so silking must occur by August 15-20. However, remember that at some point yield does not matter anymore and that timing of silage harvest is dependent upon achieving the proper moisture for the storage structure.

At the dent stage (R5), corn has accumulated 75-85% of silage yield and 60-75% of grain yield and needs about 27-32 days to avoid significant yield reductions due to frost (Table 1). In order to avoid yield reductions caused by frost, corn intended for silage should be silking by late August, while corn intended for dry grain should reach the dent stage by September 1.

 Table 1. The relationship between kernel growth stage and yield of corn for normal planting dates.

Management Options for Corn Grain Harvest
  1. Note silking dates to project calendar days to when a field will mature. Note order that field silk to plan the harvest queue. It will take approximately 55 to 60 days to get to R6.
  2. Consider selling a greater proportion of your corn acres as silage or high moisture corn.
  3. Consider locking in a price for drying fuel.
  4. Taking the dock for shrink at the elevator.
  5. Fine-tune your dryer so that over- or under-drying does not occur. Over-heating the grain in the dryer or filling the bin too fast for drying to occur will increase costs and decrease grain quality reducing profitability.
  6. Hire and train the skilled labor that will be required to monitor dryers, fans, augers, and other equipment during the drying process.
  7. Consider some field drying if moisture levels are high, but do not let corn stand in the field too long or snow may increase harvest losses due to ear droppage and stalk breakage from snow.
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Monday, June 24, 2019

Guidance When Using Corn as a Cover Crop


This year, traditional cover crop seed is hard to find. However, corn and soybean can be considered a cover crop (click here and here). Corn is deep-rooted and by the end of the growing season can produce significant residue even when planted in July. The first thing you must do, however, is talk to your crop insurance agent and make no decisions without their input.

"Farmers taking the full prevented plant indemnity should note that they cannot ever harvest the cover crop for grain or seed. RMA rules allow, only after September 1, grazing and harvest as hay (for bedding or feed) and now for silage, haylage or baleage. If a farmer wants to harvest it as grain or seed, then they should declare it as an alternative crop and only collected the partial (35%) prevented plant indemnity."  --- Paul Mitchell, UW Ag Economist

The end of the late planting period is set by USDA-RMA (Risk Management Agency) and is posted for most of Wisconsin as June 25 for corn grain and June 30 for corn silage. A farmer is not allowed to take the full prevented plant indemnity, using the same crop as a cover crop before these dates. If planted before these dates, the farmer should report it as late planted with a reduced guarantee.

As corn planting moves into June, yield swings (risk) increases. Some years can result in good grain yields, other years not so much. Early June planting dates often produce high yielding corn silage of good quality. Late June planting dates are difficult to predict for grain or silage production. Planting corn in July rarely results in adequate grain production so silage quality is poor. Corn makes an excellent "emergency" forage when planted in July. During 2005 and 2006, corn planted July 1 had forage yields ranging from 5.9 to 7.7 Tons Dry Matter / Acre (T DM/A). For corn planted July 15, forage yields were 3.5 to 5.6 T DM/A, and corn planted July 31 forage yields were 0.7 to 2.8 T DM/A.

The following agronomic guidance is given when growing corn as a cover crop. The goal of a cover crop is to protect the soil from erosion (wind and water), to improve water quality by capturing nutrients, to build organic matter, and to suppress weeds. Ultimately the decision to use corn as a cover crop is the cost of production. Typically, it would cost $400 to $450 per acre to establish corn.

Practices that maintain ground cover or establish a crop canopy quickly include:
  • Seed: Conventional hybrids and open-pollinated varieties are less expensive than bio-engineered hybrids. Neither seed nor grain from bio-engineered corn hybrids can be used as cover crop seed. Upon purchase of bio-engineered hybrids, farmers sign a contract that: 1) limits usage of grain to specific end product channels, 2) restricts ownership of bio-engineered traits, and 3) requires a refuge (stewardship). There has been some discussion of using the F2 (grain) of 2018 production ("bin-run" seed/grain). A 10-20% grain yield drag would be expected for F2 seed, however, little grain yield is expected anyway with July planting dates. Using bin-run grain as seed might be possible for conventional hybrids and open-pollinated varieties. Check seed labels and grower agreements to make sure. Again, it is illegal to use bio-engineered hybrids. For specifics about contracts for bio-engineered hybrids, see https://www.agcelerate.com/Home.
Performing any ONE of the following practices, if different from the current on-farm commercial production practice, indicates that the objective of growing corn for grain has changed to the objective of growing corn as a cover crop.
  • Plant population and seed costs: Higher populations lead to faster ground cover and helps with weed suppression. Minimum populations upwards of 35,000 plants/A are needed for corn as a cover crop. However, seed costs can also be prohibitive for higher populations.
  • Narrow row spacing: Corn is a row crop. Using a narrower row corn planter (< 30-inches), twin-row planter, or a grain drill can lead to faster ground cover by the corn canopy and weed suppression. Criss-crossed rows can lead to quicker canopy cover. 
  • Crop rotation: Rotating crops helps with interrupting pest cycles and promotes early growth and quicker canopy coverage. The choice of the cover crop this year should be based upon the subsequent crop intended next year. For example, if soybean is planned for the field next year then corn (or some grass crop) should be the cover crop this year.
  • Planting into residue: Seeding into fields with > 30% residue provides some ground cover between planting and canopy establishment. 
  • Pesticides: Herbicides should be used to help with weed control. Use care about pre-grazing and/or pre-harvest restrictions after September 1.
  • Nitrogen: The most important nitrogen applied to corn is the first 40 to 60 lb N/A. Even this may not be needed if N credits can be taken. Reducing N rate would improve cost of production, especially since little grain is expected.
July plantings rarely result in grain production in Wisconsin. A killing frost usually occurs during September or early October. If grain is produced and kernels develop beyond the milk to dough (R3-R4) stage then the crop should be cut with a haybine.

Further Reading

Conley, S., J. Lauer, and P. Mitchell. 2019. Soybean and Corn are Considered Cover Crop Options in WI

Mitchell, P. 2019.  Can I Use Corn or Soybeans as a Cover Crop on Prevented Plant Acres?

Mitchell, P. 2019.  Crop Insurance: Late and Prevented Planting and Replant

Tuesday, April 9, 2019

How Thick Should I Plant My Corn? What are other farmers doing?

Farmers continue to increase corn plant populations in Wisconsin and the U.S. Midwest. Every year as part of the Objective Yield Survey, the USDA-NASS counts plants in September at 150 locations in Wisconsin. Similar data collection is done in other corn producing states of the U.S. Midwest. Corn plant density in Wisconsin during 2018 was the highest ever measured at 30,650 plants/A. In 2018, Illinois had the highest plant density at 32,000 plants/A, followed by Iowa (31,100) and Minnesota (30,900).

In 1982, corn plant density ranged from 19,400 to 22,200 plants/A. Minnesota has consistently had higher average corn plant density than other states (Figure 1). In Wisconsin plant densities were 20,300 plants/A in 1982. Plant density has since increased at the rate of 267 plants/A*yr. Iowa and Illinois have had the greatest rates of change at 308 plants/A*yr.

Figure 1. Corn plant density changes over time for states in the U.S. Midwest Corn Belt. The rate of change (slope) in plants/A*yr since 1982 is reported for each state. Data derived from USDA-NASS.
Adjusting plant density for your fields is one of the key production decisions for producing high yielding corn. Clearly farmers are adjusting plant densities higher. Farmers still have numerous questions about plant density including:

  1. What plant density achieves maximum yield (MYPD)? 
  2. What plant density achieves the economic optimum (EOPD)? 
  3. Are the MYPD and EOPD the same for grain and silage?
  4. Do hybrids differ for MYPD and EOPD?
  5. Do fields differ for MYPD and EOPD?
  6. How does risk change, especially during years of drought or lodging?
  7. What happens to plant bareness?
  8. Do precision farming variable rate technologies make a difference? 
Over the next few articles we will try to address some of these questions.There is likely no standard recommendation for achieving MYPD or EOPD given that hybrid, environment, and economics (grain price and seed price) affect these measures. Rather MYPD and EOPD are moving targets where if we can get to within 95% of these values, it might just have to be good enough.

One approach that might be useful for your farm is to plant fields with a target plant density based upon your experience. Then for one round (or pass) in a couple parts of the field, increase plant density 10% (Figure 2). If harvest yield is affected, then adjust plant density the following season. If not, you are out the difference of ROI for seed.

Figure 2. An example of using reference strips for testing maximum yield plant density. Plant most of field to plant density based upon experience. In one strip (ideally 2 or 3) increase plant density 10%. Measure yield at harvest.

Thursday, April 4, 2019

Brown Midrib and Leafy Corn Silage Performance + A New BMR Economics Calculator

Commercial corn hybrids grown in Wisconsin are often marketed to dairy farmers as "silage-specific." In the UW Corn Performance Evaluation Trials, conventional hybrids have similar yield and quality as bio-engineered corn hybrids. However, we often see yield and quality differences between silage-specific "leafy", brown midrib (bmr), and conventional/bio-engineered hybrids. In addition, companies often market newer 3rd- and 4th-generation silage-specific hybrids implying that breeding progress has improved performance.

Brown midrib corn (picture above) has a distinctive brown midrib on the corn leaf. These hybrids typically have greater digestible energy in the stover (stalks and leaves). Leafy hybrids have 2-5 more leaves above the ear compared to conventional hybrids.

Figure 1 shows the relationship between Milk per Acre (yield) and Milk per Ton (quality) for bmr and leafy hybrids. In most years leafy hybrids tend to be average for Milk per Acre and below average for Milk per Ton. BMR hybrids tend to be below average for Milk per Acre and above average for Milk per Ton. For either hybrid type there does not seem to be a trend for newer generation hybrids.
Figure 1. Mean Milk 2006 relative performance of Brown midrib and Leafy hybrids in the UW Corn Performance trials. The origin is the overall average of all hybrids tested between 1995 and 2018 (N= 38,664 plots). BMR plot total= 623 and Leafy plot total= 1538. Difference = overall hybrid average – trial average, Code above symbol= Year
Both bmr and leafy hybrids have lower than average starch content compared to the overall mean of all hybrids in the trial ultimately affecting both yield and quality (Figure 2). Leafy hybrids have average ivNDFD, while bmr hybrids have above average ivNDFD.
Figure 2. Mean starch and ivNDFD relative performance of Brown midrib and Leafy hybrids in the UW Corn Performance trials. The origin is the overall average of all hybrids tested between 1995 and 2018 (N= 38,664 plots). BMR plot total= 623 and Leafy plot total= 1538. Difference = overall hybrid average – trial average, Code above symbol= Year
Many research reports have concluded that bmr corn silage increases milk production in cows. Our data consistently shows higher Milk per Ton, but lower Milk per Acre yield due to lower forage yield primarily due to grain yield. Since there is typically no premium paid for higher quality corn silage, I have often said, "Buy all of the bmr corn silage you can buy, but be careful about growing it on your farm." Breeding progress has likely improved silage-specific corn hybrids, but there is a corresponding genetic improvement going on with conventional and bio-engineered hybrids as well.

The BMR Corn Silage Calculator: What are the economic trade-offs for yield and quality?

To better understand the economic effect of bmr corn in dairy operation, Dr. Randy Shaver et al. have developed a spreadsheet that can be downloaded here and here. This MS Excel spreadsheet calculates milk production of brown midrib (BMR) corn silage hybrids versus conventional  hybrids. The spreadsheet calculates differences based cow herd size. Dr. John Goeser (Rock River Labs and adjunct UW faculty) has produced a video explaining how to use the spreadsheet here.

Wednesday, March 20, 2019

Corn Response to Banded Fertilizers at Planting

 
Banding fertilizer around the corn seed during planting is a common practice in the northern Corn Belt. Corn planting is frequently delayed in this region due to cold, wet soils, which result in slow root growth and limited uptake of nutrients during early developmental stages.

The last major evaluation of banded fertilizer in Wisconsin was conducted between 1995 and 1997 (Bundy and Andraski, 1999). Results indicated that full-season corn hybrids increased grain yield with banded fertilizer when planted late. Since then significant production changes have occurred including higher yields using transgenic crops, improved planting machinery and implements, and continued increases in soil nutrient levels. Growers question whether starter fertilizer is even necessary for modern corn hybrids and production practices, yet, often it is applied as “insurance.” Our objective was to evaluate the agronomic response of corn to banded fertilizer.

Plots were established at 11 locations (Arlington, Janesville, Montfort, Fond du Lac, Galesville, Hancock, Marshfield, Chippewa Falls, Seymour, Valders, and Coleman). Fertilizer treatments included: 1) an untreated check, 2) seed-placed fertilizer (10-34-0-1(Zn)) applied in the seed furrow at 4.1 gal/A, and 3) starter fertilizer (9-11-30-6(S)-1(Zn)) applied at 200 lb/A as a band 2 in. to the side of the row and 2 in. below the seed. Split-plots were eight to sixteen corn hybrids ranging in RM by 5-d increments from 80 d- to 115 d-RM. An emphasis was placed upon longer-season hybrids at each location and selection of hybrids differing in emergence vigor. Corn was harvested and yields determined mechanically from the center two rows of each four-row plot.

Figure 1. Corn grain yield response to banded fertilizer. Values are are derived from 578 GxE means and averaged across 2017 and 2018. Research is funded by the Wisconsin Fertilizer Research Council.

During 2017 and 2018 across all locations, significant differences were found for fertilizer treatment (Figure 1). Overall, starter fertilizer produced greater grain yield than seed-placed fertilizer and the untreated check. On average starter fertilizer (228 bu/A) increased grain yield up to 2.4% more than seed-placed fertilizer (224 bu/A) and the untreated check (223 bu/A). During 2017 and 2018, 5 of 11 locations had a significant response to fertilizer treatment. Consistent response across locations were seen at Arlington, Fond du Lac and Marshfield. One more year of research will be conducted during 2019.

The response of corn grain yield to starter fertilizer has been studied extensively in the United States, but the specific combinations of environmental conditions and agronomic factors that result in consistent responses remain unclear. An overall goal of this project is to predict when and where banded fertilizer will provide an economic return for the farmer. For each replicate soils were sampled and tested for nutrients. At the V5-V6 stage of growth, plants from each hybrid were sampled and tissue tests determined plant nutrient concentrations.

Further Reading

Bundy, L.G., and T.W. Andraski. 1999. Site-Specific Factors Affecting Corn Response to Starter Fertilizer. Journal of Production Agriculture 12:664-670.

Additional data:

Table 1. Corn grain yield (bu/A) response to banded fertilizer during 2017.


Table 2. Corn grain yield (bu/A) response to banded fertilizer during 2018.

Thursday, March 14, 2019

Corn Seed Survival: An update

After a corn seed is planted, it is a wonder that the seed can survive and return 400 to 600 fold or more. If Wisconsin's cool, wet spring soils do not kill the plant through imbibitional chilling, then seed rotting pathogens or hungry insects can attack and kill the seed. Once the plant emerges, it is subject to even more biotic and abiotic stresses that can often kill the plant. Even management operations like wheel traffic and cultivator blight can inflict significant harm. It is a wonder ...

I often get the question, "How much seed survives to produce grain yield?" The question is motivated by the fact that seed costs have risen dramatically in the bio-tech era of corn hybrid development (1996 to present). Some of the rising cost of seed is due to growers planting fields to higher plant densities. Between 1982 and 2017, growers in IA, IL, IN, MN, and WI have increased plant population at the rate of 261 to 309 plants/A*yr (USDA-NASS, click here). In our experiments, the corn plant density that produces maximum yield has been increasing over time at the rate of 260 plants/A*yr.

However, most of the rising seed cost is due to the use of bio-engineered traits in modern corn hybrids (USDA-ERS, click here). In the 1990s, a high performing adapted corn hybrid cost about $25 to $30/A ($80 to $125 per 80K bag or $1.00 to $1.56 per 1000 seeds). Today, typical retail seed prices are $100 to $150/A ($250 to $350 per 80K bag or $3.13 to $4.34 per 1000 seeds).

Since both seed cost and field plant density are increasing, growers are increasingly concerned about how much seed actually survives to emerge and grow into a plant that produces grain yield. In a previous article I summarized the effects of planting date and environment on corn seed survival (click here). This article adds more data to the discussion and looks at recent trends in corn seed survival.

Prior to 2008, we planted corn hybrids in UW trials by over-seeding and hand-thinning back to a uniform plant density. In 2008, we purchased a precision plot planter and dropped a uniform 34,100 seeds/A at every test site during the 2008 to 2015 planting seasons. In the winter of 2015, we had the planter refurbished and upgraded with new software set to drop 34,850 seeds/A since then. At harvest, plant population was measured on ~10% of the plots. All data collected since 2008 (N= 12,036 plots) were used in the analysis.

Seed survival in the traditional corn hybrid trials where chemical seed treatments are used, averaged 91% (Figure 1), and depended upon environment (year and location), cropping system, and seed company. Seed survival during 2012 (drought) was lowest at 82%, while seed survival was highest at 95% during 2009 (wet spring). In organic trials where conventional chemical seed treatments cannot be used, seed survival was lower averaging 83%. Seed survival was lowest at 68% during 2008, while seed survival was highest at 91% during 2009, 2014 and 2018.

Within the UW Corn Hybrid Evaluation program we have tested over 200 unique seed treatment combinations. However, there is no strong trend for seed survival improvement over time in the traditional trials, while there seems to be some improvement in the organic trials.

Figure 1. Corn seed survival across years in traditional and organic cropping systems. Data are derived from UW Corn Hybrid Performance Trials conducted between 2008 and 2018 (N= 12,036 plots).
Seed survival averaged 90% at test sites in northern Wisconsin, and 94% in southern Wisconsin (Table 1). Marshfield and Seymour had seed survival rates of 88 to 89%. Both Chippewa Falls and Hancock are sandy sites and had low seed survival (90%). Lancaster seed survival was lower due to tillage issues that caused crusting in many years. Arlington and Fond du Lac had the greatest seed survival at 96%.

Table 1. Corn seed survival in traditional trials across locations and production zones in Wisconsin. Data are derived from UW Corn Hybrid Performance Trials from 2007 to 2018 (N= 12,036 plots).

The choice of seed company also had a significant effect on seed survival. In the traditional trials, one company had a seed survival rate of 82%, while another company had a survival rate of 97% for a range of 15% (data not shown). In the organic trials, one organic seed company had a seed survival rate of 72%, while another averaged 86% for a range of 14% among companies. This range in company performance is likely due to choice of seed treatment and seed quality effects.

There are numerous factors that influence corn seed survival including hybrid, soil type, seed treatment, tillage system, cropping system, planting date, and environment. Traditionally, we have used a survival rate of 90%. More recent data indicates that 90 to 92% is a reasonable survival rate. However, seed survival at some locations and years can be as high as 95% and would need to be taken into account in order to achieve the target plant density.

Tuesday, March 12, 2019

The Corn Yield Gap in Wisconsin

Corn yields have been increasing in Wisconsin at the rate of 2 bu/A*yr (USDA-NASS) and there is no indication that corn yields are plateauing. The highest recorded state average yield occurred in 2016 at 178 bu/A. In 2012, Jeff Laskowski (Portage county) recorded the highest corn yield in Wisconsin at 327 bu/A. In the Wisconsin NCGA Corn Yield Contest yields above 300 bu/A have been recorded 21 times.

"Yield gaps" are the difference between potential crop yield and actual farmer yield. Potential yield is defined as the yield of a hybrid when grown in environments to which it is adapted; with nutrients and water not limiting; and with pests, diseases, weeds, lodging, and other stresses effectively controlled. Previous corn yield gap estimates from around the world have ranged from 11 to 84%. Lower yield gaps are typically seen under irrigated conditions. It is not clear if potential yield is determined by soil type or if eliminating water and nutrient stresses is more important. Political boundaries and technology availability also affect potential yield.

The challenge in understanding a yield gap is determining potential yield. The gap depends upon the method used to estimate yield potential. Some researchers use crop modeling techniques, others use yield maps from precision farming, or various statistical techniques, or yields from ag research station experiments, etc. Regardless, potential yield is location specific. The larger the geographical scale used to estimate potential yield and farmer yield, the more difficult it is to estimate a yield gap and to identify management practices that reduce or eliminate the yield gap.

The NCGA Corn Yield Contest consists of three categories: rain-fed, irrigated and conservation tillage. Overall winners of the contest over time regardless of category were used to set the potential yield for corn. Although most winners in the NCGA contest are from southern Wisconsin where farmers use longer-season hybrids with greater yield potential, the overall record and 8 of 21 yields above 300 bu/A are from north central Wisconsin. USDA-NASS average corn yields were used for farmer yields.

The regressions in Figure 1 show farmer and potential yield for Wisconsin. USDA-NASS yield (farmer yield) has increased from 96 bu/A in 1983 to 166 bu/A in 2018. The Wisconsin NCGA winners (potential yield) have increased yield from 184 to 320 bu/A. The yield gap in 1983 was 87 bu/A (47.6%), while the yield gap in 2018 was 155 bu/A (48.3%). The yield gap was widest in 2012 at 207 bu/A (63%) and narrowest in 1997 at 87 bu/A (40%). Clearly corn yields are increasing, however, the yield gap in 2018 is relatively the same as the yield gap in 1983 at about 48%. Surprisingly, the yield gap among NCGA categories is not statistically different (data not shown).

Figure 1. Corn yield gap between USDA average yield (farmer yield) and winners of the Wisconsin NCGA yield contest (potential yield). Data derived from USDA-NASS and NCGA corn yield contest winners.

Wisconsin corn production is a highly developed, sophisticated, high-yielding production system making it unlikely that variation exists in the availability of technology. Many farmers use the best technology available, however, some farmers choose not to employ the same level of technology as yield contest winners. At the farm level, yield gaps in many fields can be reduced by relatively simple changes in management practices. Yield maps are one way to identify yield gaps within a field and on your farm.

Friday, February 15, 2019

"One and Done" or a Disease Problem Here to Stay: Planning for Tar Spot in 2019

Map showing Midwest U.S. counties where tar spot infections were confirmed.
Figure credit:
Kleezewski et al., 2019
In 2018, southwest Wisconsin was especially hard hit with a new disease called Tar Spot, Phyllachora maydis. I have talked to many growers this past winter about the disease and what might be done for the coming season. However, we have limited experience with the disease and it's implications for yield. At Montfort we had a significant tar spot infection in our hybrid trial plots. It was the only disease present. Dr. Damon Smith was able to rate each plot for the disease. Later we combine harvested each plot measuring yield, moisture, lodging and test weight. Dr. Smith rated ear leaf disease severity of 45 to 50% which correlated to yield impacts of 40 to 60 bu/A (18 to 27%). This is a disease that needs to be reckoned with in the future.

So how do we plan for 2019? Is tar spot a "one and done" disease, or is it here to stay? For any disease to be a problem, it needs a susceptible host, a virulent pathogen and favorable environmental conditions. All conditions have to be present. Since tar spot has affected yield during one growing season, the prudent thing to do is plan for the disease in the future.

To reduce tar spot development and severity, Kleezewski et al. (2019) recommends managing residue, crop rotation, using hybrid resistance, and using fungicide. Of these recommendations, crop rotation might be the easiest management tool to implement. Many fields in southwest Wisconsin are no-till planted so burying residue is problematic. Using hybrid resistance might be effective, but little public information is available about hybrid/family disease reaction of commercial hybrids sold to farmers. Some fungicides may reduce tar spot, but there is little data about application timing that provides an effective and economical response.

Further Reading

Kleezewski, N., M. Chilvers, D. Mueller, D. Plewa, A. Robertson, D. Smith, and D. Telenko. 2019. Tar Spot. Crop Protection Network. CPN-2012 – Corn – Tar Spot. https://cropprotectionnetwork.org/download/5830/ 

Smith, D., B. Mueller, J. Lauer, K. Kohn, and T. Diallo. 2018. The Effect of Tar Spot on Corn Hybrids in Wisconsin in 2018. see Badger CropDoc website https://badgercropdoc.com/category/corn/corn-disease/tar-spot/  (verified 2019Feb15)

Smith, D. 2019. Video: Tar Spot Management on Corn, A Wisconsin Perspective. Click here or click here (YouTube).