With soils continuing to be very wet in parts of Kansas, more questions have been coming in about the effect of delayed planting on corn yield. A series of studies at K-State looking at delayed corn planting was conducted a few years ago (Fig. 1).
Three hybrid maturities were tested: 100-, 108-, and 112-day. Over the two years and three locations (Belleville, Manhattan, and Hutchinson), there were three distinct growing season environments (as related to the environmental stress):
- Low Stress – where rainfall was favorable during the entire growing season
- Early Stress – where cool temperatures and wet conditions limited early corn growth, followed by favorable growing conditions
- High Stress -- where conditions (rainfall and temperatures) were favorable early in the season, but the mid-summer was hot and dry
In the Low Stress environments, yields were reduced by less than 20% when planting was as late as mid-June. Yields were not statistically different for any planting date before May 20 (starting from early April). Maximum yield in these non-irrigated environments was 176 bu/acre. The yield responses were similar for hybrids of all maturities.
In the Early Stress environments, yields actually increased as planting was delayed until late June. This response was similar for all hybrid maturities. These environments had favorable temperatures and rainfall throughout July and early August. Maximum yield in these environments was 145 bu/acre.
In the High Stress environments (hot, dry summer conditions), yields dropped by about 1% per day of planting delay, depending on hybrid maturity. The shorter-season hybrids had the best yields if they were planted before late May (max. yield = 150 bu/acre), but all hybrids had yield reductions of more than 50% when planting was delayed until early to mid-June.
In many ways, the current growing season is shaping up like the “Early Stress” scenario above, with cool conditions early in the season. Will this cool spring be followed by favorable temperatures and rainfall, or by hot and dry conditions during the rest of the growing season?
While long-term weather predictions are highly unreliable, the National Weather Service Climate Prediction Center (http://www.cpc.ncep.noaa.gov/) three-month outlook indicates a 40% likelihood of above-normal precipitation and near-normal temperatures for most of the state.
Figure 1. The top chart (LS, or Low Stress) shows how little corn yields changed as planting dates got later when growing conditions were good through the remainder of the season. The middle chart (ES, or Early Stress) shows that corn yields actually increased with later planting dates when conditions were too cool and wet early, but then became more favorable. The lower chart (HS, or High Stress) shows how dramatically corn yields decreased when conditions were favorable early in the season, but the mid-summer was hot and dry. H1 refers to the 100-day hybrid. H2 refers to the 108-day hybrid. H3 refers to the 112-day hybrid.
Using a Web-Support Decision Tool: “Useful to Usable” (mygeohub.org)
A web-support decision tool called “Useful to Usable” (mygeohub.org) can help in making hybrid maturity decisions when planting late. For example, for the Manhattan location, if a 111-comparative relative maturity (CRM) corn hybrid was planted on April 15, it will take 2,670 growing degree days (GDD) from planting to physiological maturity (black layer). That means it will reach black layer around the last week of August or beginning of September. The earliest first freeze experienced at this location was early October (in 1985); thus, planting in mid-April planting does not risk early termination of the crop by fall frost (Fig. 2). Of course, we are well past that date now.
Figure 2. Corn growing degree day tool for a 111-CRM planted April 15, 2017. From https://mygeohub.org/groups/u2u/gdd (“Useful to Usable” website).
If the planting date is Friday, May 25, without changing the CRM, the final GDD is similar. Nonetheless, black layer will be reached sometime from mid-September to mid-October. This situation increases the risk of damage from an early fall freeze, but the impact is predicted to be minimal (Fig. 3).
Figure 3. Corn growing degree day tool for a 111-CRM planted May 25, 2017. From https://mygeohub.org/groups/u2u/gdd (“Usable to Useful” website).
If planting is delayed to June 1, the same CRM corn hybrid will reach maturity sometime from about early October to the beginning of November. This will increase the likelihood of a killing frost (high probability for frost by mid-October), which will result in a low test weight and high moisture content in the grain due to a shortening of the grain filling and drying down period (Fig. 4 – left panel). By keeping the same planting time, but switching to a shorter CRM corn hybrid (e.g. 105 CRM), corn would reach black layer about the same time as the 111-CRM hybrid planted May 25 (Fig. 4 – right panel). Thus, changing to a shorter CRM would increase the probability of reaching maturity with a small risk of being impacted by an early fall freeze.
As you move south and east from Manhattan, the risk of early termination from a fall freeze will decrease, but the risk will increase as you move north and west from Manhattan.
Figure 4. Corn growing degree day tool for a 111-CRM (left panel) and for a 105-CRM both planted June 1, 2017. From https://mygeohub.org/groups/u2u/gdd (“Usable to Useful”).
So, depending on your location and what you believe will happen during the rest of the growing season, delayed planting may or may not have much of an effect on corn yields.
When making decisions on delayed planting of corn, crop insurance considerations are often an important factor as well as agronomic considerations.
Kraig Roozeboom, Cropping Systems Agronomist
kraig@ksu.edu
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
ciampitti@ksu.edu
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