Published on Friday, May 25, 2018
The continued rains have kept farmers out of the fields for most of the month of May. With some dry stretches in the forecast, many will be returning to the field soon to continue (or begin) planting. Here are a few things to keep in mind when planting late.
Field Conditions Still Matter
When the calendar tells us that planting season should be well behind us, it’s tempting to push the envelope and plant before field conditions are optimal so we can cover more acres before the next rain hits. However, planting too early into poor conditions may come back to haunt us, especially in late-planted crops.
The graph below depicts emergence timing at three different planting dates. Each color on the bar represents a different day of emergence. Planting into wet conditions caused the corn to take longer to emerge, with fewer plants emerging on the first day. The corn that was planted three days later into ideal conditions finished emerging on the same day as the first planted corn, with a far higher percentage of plants emerging on the first day.
Why is this important? Ideally, we want all of our corn plants to emerge at the same time, preferably within 24 hours. When emergence occurs over an extended period of time, it results in differences in growth stages between plants, which causes the late emerging plants to act more like weeds —competing with the early-emergers for water and nutrients but not producing much yield.
The data below from the Yield vs. Emergence study at Beck’s Practical Farm Research (PFR)® site illustrates this point. At emergence, our PFR team in Ohio flagged all the plants that emerged in the first 24 hours. They then flagged all the plants that emerged 24 hours later. In the fall, they hand harvested the plot and sorted the ears based on when the plant emerged. After shelling and weighing the corn, they calculated the yield based on emergence date. As expected, the later-emerging corn yielded much less than the earlier-emerging corn.
The point I want to emphasize as we move into a late planting season is the difference in the yield penalty from early planting to late planting dates. When planting late, later-emerging plants cost four times as much in yield compared to planting early. Since planting into poor conditions leads to more late-emerging plants, it’s critical to wait for ideal conditions when planting late.
There are a number of considerations to keep in mind when choosing the correct planting population for soybeans. One of the key factors is planting date. As we plant later into the season, we reduce the amount of time that our soybean plants spend in the vegetative growth stages before they begin the reproductive growth stages after June 21. Therefore, this will likely result in shorter soybean plants with a lower potential number of nodes and pods. In order to maintain yield potential, we need to increase our planting population to help offset this. When planting after May 15, I recommend increasing your planting populations by 10,000 seeds/wk. to account for the shorter growing season and less vegetative growth potential.
Soybean Maturity Concerns
Last week, I shared information to help in making a good decision about whether or not to switch to planting earlier maturity corn hybrids when planting late. You can view it on my blog by clicking here.
Corn matures based on accumulated heat units—it does not progress to the next growth stage until it accumulates the required number of growing degree units (GDUs). While corn does compensate slightly for late planting, it will not reach maturity until it has accumulated the heat units it needs. Soybeans are very different in that they regulate maturity by day length. June 21 is the summer solstice, or longest day of the year. After that date, the days begin to get shorter and soybeans will begin to enter their reproductive growth stages. This transition happens whether the soybean plants are eight inches tall or three feet tall.
Maturity ratings in soybeans are a reflection of how much time the soybeans will spend in each reproductive phase. Fuller-season soybean varieties will spend more time in each phase than shorter-season varieties. Planting date has some effect on this process, but it is minimal. As a rule of thumb, every five to seven days of delayed planting will usually result in one day of delayed harvest, regardless of the maturity. In fact, fuller-season varieties tend to maintain a higher yield potential when planted later than shorter-season varieties. As long as you don’t chose a soybean variety that is far outside of the typical maturity range for your area, there should be no reason to switch soybean varieties for late planting.
If you have any questions about this information, feel free to reach out to myself or your local Beck’s representative.
Author: Mike Hannewald
Categories: N Indiana, Michigan