Battle for the Belt: Episode 19

*Based on leaf collar method as defined by Abendroth, et al. (2011), Corn Growth and Development, PMR 1009 Iowa State Univ. Extension, Ames, IA. **Approximate GDDs between growth stages and cumulative GDDs since planting. Source:  Nielsen, RL. (2011). Predicting Corn Grain Maturity Dates for Delayed Plantings. Corny News Network, Purdue Extension. [online] kingcorn.org/news/timeless/RStagePrediction.html and Nielsen, R.L. (2021). Grain Fill Stages in Corn. Corny News Network, Purdue Extension. [online] kingcorn.org/news/timeless/GrainFill.html

Accumulated Growing Degree Day (GDD) as of July 10^th, 2023:
The accumulated GDD numbers at our three research sites are presented in Table 2. Taking the Wooster site as the example, according to our field notes, crop stages were consistently at the point where GDD estimations would have suggested:

Planting date 1, planted on April 14: 996 GDDs; V11-V12 stage

Planting date 2, planted on April 27: 934 GDDs; V10 stage

Planting date 3, planted on May 11: 881 GDDs; V9 stage

Planting date 4, planted on May 30: 687 GDDs; V7 stage

Planting date 5, planted on June 21: 381 GDDs; V4 stage

To monitor GDD accumulation during the growing season, users can follow the weekly report about Ohio Crop Weather provided by the United States Department of Agriculture National Agricultural Statistics Service (USDA-NASS), available online at: www.nass.usda.gov/. Once there, you can find your closest location and proceed with the estimations. Note that you should be getting a weekly number rather than a daily number. Once you have the weekly GDD value, you can aggregate for the growing season. Alternatively, there is an open-source tool that can help in that process Useful to Usable (U2U). The tool helps to develop different scenarios, it provides county-level estimates based on historical GDDs accumulation, planting dates, relative hybrid maturities, GDDs to black layer, and historical freeze temperature dates.

As with any system, the GDD approach has short­comings. One potential issue is the difference that occurs when accumulating GDD from the planting date versus the emergence date. When this occurs, similar maturity hybrids may vary by 100 to 150 GDDs (the average GDDs required for emergence). Although most companies use the 86/50 cutoff method described above, others use different methods that can lead to different results. Lastly, under delayed planting situa­tions, research has suggested that GDD requirements for maturity may be reduced, often referred to as growing degree compression. At any rate, these are just pieces of information to keep in mind when running your own estimations, but the GDD system alone has certainly important applications across a wide range of farming conditions.

Battle for the Belt location updates (as of July 17, 2023)
At the Wooster site, we are moving along. For soybean planting date one, two, three, four, and five, growth stages are R1/R2, V10, V8, V5, and V1. Planting date one did not reach full canopy yet but is branching and flowering. There are signs of disease and insects; however, leaf area affected is minimal and neither should cause yield loss. The corn stages are as follows for planting date one, two, three, four and five: V11, V10, V9, V7, and V4. There was evidence of anthracnose on the oldest corn leaves. The anthracnose will cause early leaf loss in corn; however, this disease is not a concern for yield as it normally only eliminates the oldest leaves. Japanese beetle was found in both corn and soybeans causing a small amount of defoliation.At the Western site, the planting dates, one, two, and three, are flowering. Each of these planting dates have closed canopies and are uniform. Planting date four is not uniform in stage within the plots; there are plants between V4 and V8. Planting date five is at V3. The corn at this location is our furthest along and the hybrid differences in the plots are exaggerated during pollination. The shortest day hybrid was fully tasseled with silks out that had red tint, which means pollination has been successful. The later maturing hybrids were not tasseled. The earliest maturing hybrid in planting date two was also silked and tasseled, while no other plot in panting date two was. The uniformity within single hybrid plots were also lacking with some plants fully tasseled, silked, and, pollinated and some that were not even tasseled.

At the Northwest site, the soybean stages were as follows for planting date one, two, three, four, and five: R2, R2, R1, V10, and V5. The corn was at R1 in the earliest maturing hybrid for planting date one and two. Though this consideration is interesting because this particular hybrid was 75% silked but less than 50% showed tassels, showing that the ear/tassel are completely synced (Figure 1). The rest of the hybrids in planting date one were V16 and planting date two was V14. Planting date three, four, and five are V13, V9, and V7.

At the Western site, the planting dates, one, two, and three, are flowering. Each of these planting dates have closed canopies and are uniform. Planting date four is not uniform in stage within the plots; there are plants between V4 and V8. Planting date five is at V3. The corn at this location is our furthest along and the hybrid differences in the plots are exaggerated during pollination. The shortest day hybrid was fully tasseled with silks out that had red tint, which means pollination has been successful. The later maturing hybrids were not tasseled. The earliest maturing hybrid in planting date two was also silked and tasseled, while no other plot in panting date two was. The uniformity within single hybrid plots were also lacking with some plants fully tasseled, silked, and, pollinated and some that were not even tasseled.

Keep following the ‘Battle for the Belt’ this growing season to learn more and get further updates! You can find the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel.