By Joe Lauer, University of Wisconsin Corn Agronomist
The 2015 growing season is rapidly coming to a close. Weather during 2015 has been similar to the 30-year normal (click here and select year under "Weather Graphs" on left side). So 2015 will be characterized as an average year and will be useful to test recommendations based upon average seasons. The more interesting years are when weather is more extreme to see how well recommendations based upon averages hold up.
This year saw delayed planting in northeast Wisconsin. Also, an early season (early July) wind storm along the southern three tiers of counties lodged many fields. Corn that did not snake back up was poor yielding. Northern corn leaf blight was especially prevalent this year.
Use Your Time in Combine Seat to Scout Fields
Harvest provides an opportunity to scout your fields. As you travel through the field, you can observe various types of problems that may have occurred during the growing season. Weeds that were not controlled would be one of the most obvious problems that will show up. With the increase in weeds that are resistant to various herbicide classes, it is important to identify these problems as early as possible in order to control increases in populations and movement of the weed. This may also provide some opportunity to begin managing the problem this fall.
Insect and disease problems can also be detected in the fall. Note if particular varieties seem more susceptible to an insect or disease. If one variety or hybrid seems to be more susceptible to disease pressure or insect pressure, then this information could be used in variety or hybrid selection for next year. If all hybrids or varieties are affected similarly, then the cause of the problem needs to be identified to aid in selecting management options for next year’s crop.
Evaluating Test Plots
This is also the time of year when on-farm strip plots are evaluated. Field variability alone can easily account for differences of 10-50 bushels per acre. Be extremely wary of strip plots that are not replicated, or only have "check" or "tester" hybrids inserted between every 5-10 hybrids. The best test plots are replicated (with all hybrids replicated at least three times).
Don't put much stock in results from one location and one year, even if the trial is well run and reliable. This is especially important in years with tremendous variability in growing conditions. Years differ and the results from other locations may more closely match your conditions next year. Use data and observations from university trials, local demonstration plots and then your own on-farm trials to look for consistent trends.
A Few Suggestions On How to Evaluate Research Test Plots:
- Walk into plots and check plant populations. Hybrids with large ears or two ears per plant may have thin stands.
- Scout for pest problems. Hybrid differences for pest resistance and tolerance should be monitored and noted all season, but will be most apparent in the fall. Counting dropped ears is a good way to measure hybrid ear retention and tolerance to European corn borers.
- Check for goose-necked stalks. This is often root pruning caused by corn rootworms. Hybrids differ in their ability to regrow pruned roots.
- Find out if the seed treatments (seed applied fungicides and insecticides) applied varied among hybrids planted, e.g. were the hybrids treated with the same seed applied insecticide at the same rate? Differences in treatments may affect final stand and injury caused by insects and diseases.
- Differences in standability will not show up until later in the season and/or until after a wind storm. Pinch or split the lower stalk to see whether the stalk pith is beginning to rot.
- Break ears in two to check relative kernel development of different hybrids. Hybrids that look most healthy and green may be more immature than others. Don't confuse good late-season plant health ("stay green") with late maturity.
- Visual observation of ear-tip fill, ear length, number of kernel rows, and kernel depth, etc. don't tell you much about actual yield potential. Hybrid differences are common for tip kernel abortion ("tip dieback" or "tip-back") and "zipper ears" (missing kernel rows). Even if corn ear tips are not filled completely, due to poor pollination or kernel abortion, yield potential may not be affected significantly, if at all, because the numbers of kernels per row may still be above normal.
- Be careful with test plots consisting predominately of one company's hybrids. Odds are stacked in their favor.
