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.