The Emergence Exploration, Part 2! Results from our 2018 Study.
Updated: Jan 24, 2019
Earlier this year, I posted a blog about the emergence studies we had conducted the past couple years. Uniform emergence is often cited as the hallmark step to reaching higher yield goals. If you can get all the plants up within 48 hours of each other, uniformity is optimized and the chance of each plant setting a uniform ear is increased. This should theoretically lead to increased yield.
Studies have shown that within a 3-4 day timeframe late emerging plants were NOT considered a weed. Other studies showed that plants at a 2 leaf delay would result in less yield. In 2017 we found that 74% of yield was attributed to plants emerging within the first 24 hours. Plants showed a 2-6% yield reduction for those emerging after 24 hours. However, plants emerging between 24 and 48 hours still contributed to overall yield. We also discussed the need for more of these studies in the 2018 growing season. We conducted another six emergence studies this year and collected the results within the last month, and here are the results! Catch up by reading about last years study here!
A Breakdown by Timeframe
Figure 1 highlights the percent emerged by site within each timeframe. First 12-48 hours shows the cumulative percent totals of emerged corn. The final emergers column shows the percent for each site that emerged after 48 hours. As you can see in Figure 1, for each site, between 65% and 100% of plants emerged within the first 48 hours. Following what we found in 2017, if we back up and look at the first 24 hours, we can see that between 31% and 68% emerged in the first 24 hours. Sites 4, 5, and 6 each had 68% emerged in the first 24 hours, and consequently had more emerged plants by 48 hours than sites 1-3, with sites 5 and 6 showing 100% emergence at 48 hours. These sites were much more consistent with ear sizes and final yield was higher.
Figure 2 illustrates this point well. The three sites that had higher levels of emergence at 24 and 48 hours were the three highest yielding sites. It is important to note that many other factors contribute to the yields, such as temperature at planting, soil conditions, growing season rainfall, etc, but it is likely that the uniformity of emergence also played a role in these yields.
Let’s take a closer look at sites 5 and 6, the two sites with 100% emergence at 48 hours. At Site 5, 37% of plants emerged in the first 12 hours, with a cumulative total of 68% in the first 24 (Figure 3). This front loading of emergence resulted in a more uniform ear size for those emerged in the first 24 hours than extending to those emerged 24- 48 hours. The distribution of ear sizes is displayed in Figure 4. The majority of plants ranged from 6-8 ounces in the first 12 hours with more variability picking up from 12 hours on.
Similar results can be seen for Site 6 in Figure 5. Here, 32% emerged in the first 12 hours, with the largest portion emerging from 12-24 hours. You can see the weight distribution is a little less uniform than at site 5, however, as we extend past 24 hours we do see a little more uneven weights and even a missing ear contributing to the final yield. Average ear weight was much closer to the 7-8 ounce range through 24 hours than the 24-48 hour timeframe.
For our 2017 data we conducted some scenario analysis to see what the optimal yields would have been if all plants had emerged within 24 hours. On our six field sites this year, if all plants had emerged in the first 24 hours and had the same average ear size as those that emerged in the first 24 hours, we would see a yield increase between 2 and 26 bushels per acre. Figure 7 illustrates this difference between optimum and actual yield. This optimal yield calculation signals an 1-18% yield loss for plants emerging from 0-48+ hours verses all coming up within the first 24 hours. There is clearly a yield advantage to getting all the plants up as quickly as possible.
In the 4 sites where emergence was not complete at 48 hours, sites 1-4, you can see that there was more yield left on the table than with the two sites that had completed emergence at 48 hours. On sites 1-4, an additional 12-26 bushels per acre could have been captured with condensed emergence. The actual emergence resulted in 4-18% reduction in yield compared to 24 hour emergence. On sites 5 and 6, the yield advantage was only 2-6 bushels for moving all emergence below 24 hours, resulting in only a 1-3% yield reduction for emergence extending to 48 hours. This shows that there is still some advantage to condensing emergence below 24 hours but still very adequate emergence and yield under 48 hours. Only a small advantage was shown by moving emergence all below 24 hours.
Overall, results were very similar from 2017 to 2018.
• The majority of yield came from the first 48 hours
• In 2017, 74% of yield was set in the first 24 hours. In 2018, 54% of yield was set in the first 24 hours.
• Ear weights were the heaviest in the first 24 hours and decreased with each subsequent timeframe
• There is a yield advantage to having all plants emerge within 24 hours. In this study, this ranged from a 2-26 bushel per acre advantage in having all plants emerge within 24 hours
• Extending emergence past 24 hours to 48 or 48+ resulted in a 1-18% yield reduction.
• There was less consequence for extending emergence from 24 to 48 hours, 1-3% yield reduction, than 24 to greater than 48 hours, 4-18% yield reduction.