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 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.