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
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. 

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  (verified 2019Feb15)

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