Corn Late-Planting

Originally written February 1, 2006 | Last updated October 16, 2012

The optimum date to plant corn in Wisconsin is around May 1 in southern and May 7 in northern Wisconsin. Early planting dates are preferred to later planting dates due to the impact on grain yield and increased drying cost of higher grain moisture in the fall.

As planting date gets later during a growing season, there comes a time when

1. hybrid maturities must be switched,
2. the use of the corn must be reconsidered (i.e. high moisture corn, silage, forage, etc.),
3. the question of whether or not corn should even be grown at all and another crop be grown in its place, and finally
4. corn is a worthy "emergency forage" and should be considered if planting a field is delayed to July.

If the decision is to continue planting corn, then consider the following:

1. Try to achieve the same target population, but possibly reduce the seeding rate because of possible increased corn emergence and survival
2. Reduce or eliminate tillage trips
3. If switching to earlier hybrid maturities then emphasize disease resistance, Bt-corn borer traits and yield potential.

Relative Maturity Switch Dates

There is an yield and moisture trade-off between full- and shorter-season relative maturity (RM) hybrids. In southern Wisconsin the yield trade-off is 1.9 bushels per RM unit. For example, a 100 d ay RM would typically yield 19 bu/A more than a 90 day RM hybrid. The highest yielding hybrids are those that utilize entire growing season and are typically full-season for maturity. Eventually full-season hybrids run out of growing season and are impacted more for grain yield than shorter-season hybrids (Figure 1). Relative maturity must be balanced against harvest grain moisture and the ensuing drying costs required to dry grain down to 15.5% moisture. Full-season hybrids are often wetter than shorter-season hybrids at grain harvest.

The date to switch hybrids depends upon corn grain price and eventual use of the crop due to drying costs (Table 1, also click here). As grain price increases, switch dates become later by 1-12 days. As drying costs increase, switch dates become earlier by 4-17 days.

Table 1. Price ratio of Energy:Corn price (i.e. $/point bu÷ $/bu corn). Partial budget subtracting harvest costs from corn price.  Data source: Arlington, 2003 to 2010.
Price of Energy (LP Gas)		Price of corn ($/bu)
$/gal	$/point bu	$3.50	$4.00	$4.50	$5.00	$5.50	$6.00	$6.50
$0.00	$0.00	0.000	0.000	0.000	0.000	0.000	0.000	0.000
$0.40	$0.01	0.002	0.002	0.002	0.002	0.001	0.001	0.001
$0.80	$0.02	0.005	0.004	0.004	0.003	0.003	0.003	0.002
$1.20	$0.02	0.007	0.006	0.005	0.005	0.004	0.004	0.004
$1.60	$0.03	0.009	0.008	0.007	0.006	0.006	0.005	0.005
$2.00	$0.04	0.011	0.010	0.009	0.008	0.007	0.007	0.006
$2.40	$0.05	0.014	0.012	0.011	0.010	0.009	0.008	0.007
$2.80	$0.06	0.016	0.014	0.012	0.011	0.010	0.009	0.009
$3.20	$0.06	0.018	0.016	0.014	0.013	0.012	0.011	0.010
Switch date:
$0.00	$0.00	May 23	May 23	May 23	May 23	May 23	May 23	May 23
$0.40	$0.01	May 22	May 22	May 22	May 22	May 22	May 22	May 22
$0.80	$0.02	May 20	May 20	May 21	May 21	May 21	May 21	May 21
$1.20	$0.02	May 18	May 19	May 19	May 20	May 20	May 20	May 21
$1.60	$0.03	May 16	May 17	May 18	May 18	May 19	May 19	May 20
$2.00	$0.04	May 14	May 16	May 16	May 17	May 18	May 18	May 19
$2.40	$0.05	May 12	May 14	May 15	May 16	May 17	May 17	May 18
$2.80	$0.06	May 10	May 12	May 13	May 15	May 15	May 16	May 17
$3.20	$0.06	May 8	May 10	May 12	May 13	May 14	May 15	May 16
Partial Budget subtracting harvest costs:
							Rate
	Grain yield (bu/A)		180	handling	($/bu)		$0.02	$0.02
	Grain moisture (%)		25.0	hauling	($/bu)		$0.04	$0.04
	Input trade-off ($/A)		$25.00	trucking	($/bu 100 miles)		$0.11	$0.11
				storage	($/bu month)		$0.02	$0.06
				drying	($/bu point)		$0.06	$0.57
				Total	($/bu)			$0.80
					$0.80	/bu
$0.00	$0.00	0.000	0.000	0.000	0.000	0.000	0.000	0.000
$0.40	$0.01	0.003	0.003	0.002	0.002	0.002	0.002	0.001
$0.80	$0.02	0.006	0.005	0.004	0.004	0.003	0.003	0.003
$1.20	$0.02	0.009	0.008	0.006	0.006	0.005	0.005	0.004
$1.60	$0.03	0.012	0.010	0.009	0.008	0.007	0.006	0.006
$2.00	$0.04	0.015	0.013	0.011	0.010	0.009	0.008	0.007
$2.40	$0.05	0.018	0.015	0.013	0.011	0.010	0.009	0.008
$2.80	$0.06	0.021	0.018	0.015	0.013	0.012	0.011	0.010
$3.20	$0.06	0.024	0.020	0.017	0.015	0.014	0.012	0.011
Switch date:
$0.00	$0.00	May 23	May 23	May 23	May 23	May 23	May 23	May 23
$0.40	$0.01	May 21	May 21	May 22	May 22	May 22	May 22	May 22
$0.80	$0.02	May 19	May 20	May 20	May 20	May 21	May 21	May 21
$1.20	$0.02	May 16	May 18	May 18	May 19	May 19	May 20	May 20
$1.60	$0.03	May 14	May 16	May 17	May 18	May 18	May 19	May 19
$2.00	$0.04	May 11	May 13	May 15	May 16	May 17	May 17	May 18
$2.40	$0.05	May 9	May 11	May 13	May 14	May 15	May 16	May 17
$2.80	$0.06	May 6	May 9	May 11	May 13	May 14	May 15	May 16
$3.20	$0.06	May 2	May 6	May 9	May 11	May 12	May 14	May 15
Harvesting costs: handling = $0.02/bu, hauling = $0.04/bu, trucking = $0.11/bu for 100 miles, storage = $0.02/bu of 25% for 4 monthes and 25% for 8 monthes, drying = $0.04/point moisture above 15.5% (assume 22.5%). Source for drying efficiency: Hoeft et al., 2000 p.328 T15.6; also Hellevang and Morey NCH-14 Table 4.

Switch dates usually occur around May 20 for most locations in Wisconsin. In southern Wisconsin, two switch dates can occur for grain (May 20 and June 1), while in northern Wisconsin only one switch date is available (May 20). The planting window is much shorter in northern Wisconsin.

Figure 1. Shorter-season hybrids (7 to 10 days M) become more economical (yield and moisture) than full-season hybrids after about May 23. Source: Lauer (Arlington, WI, 2002-2010).

The switch date decision is also influenced by the eventual use of the corn (Table 1). If the field to be planted is intended for corn silage or high moisture grain, then switch dates can be later because there is less concern about drying costs. The crop needs to achieve between 25% kernel milk for silage and black layer for high moisture corn grain yield to optimize yield.

In addition, switch dates are influenced by geographical location. There is more flexibility for southern Wisconsin than northern Wisconsin. In southern Wisconsin, we have two or more possible switch dates for grain, May 20-25 and June 1-5 (Table 2). While in northern Wisconsin, we have only one switch date May 20-25.

Table 2. Relative maturity of adapted corn hybrids for different planting dates and relative maturity zones in Wisconsin.
	Relative maturities for late planting on
Full-season relative maturity zone (planting before May 15)	May 20	June 1	June 10	June 20
80 and earlier	75- 80	75- 80 (silage)	--	--
85- 90	80- 85	75- 80 (silage)	--	--
90- 95	85- 90	75- 80	75- 80 (silage)	--
95-100	90- 95	80- 85	75- 80 (silage)	--
100-105	95-100	85- 90	75- 80	75- 80 (silage)
105-110	100-105	90- 95	80- 85	75- 80 (silage)
110-115	105-110	95-100	85- 90	75- 80 (silage)

Another factor influencing switch date is, what shorter-season hybrids do you switch to? During the winter, a lot of research often goes into selecting good high performing full-season hybrids. But as the decision to switch to shorter-season hybrids draws near, do you have enough time to adequately research and find a good performing shorter-season hybrid? Is a good high-performing hybrid available from the seed company? Remember the basics (see http://corn.agronomy.wisc.edu/AA/A082.aspx) as you select new hybrids and don't be pressured into switching into just any hybrid - make sure it is a good performer.

One last point is that late-planted corn often has increased pest pressure, especially from European corn borer (ECB). Planting a transgenic Bt-CB hybrid can help manage ECB if pressure is high.

Should Corn be Planted?

If corn planting is delayed until June 1 in northern Wisconsin and June 10 in southern Wisconsin, then growers should consider putting corn planters away and planting soybean. The low corn yields seen in June will not recover the input costs required to produce the crop. This decision is influenced by corn price, price of the alternative crop (usually soybean) and the proportion of farm acres of each crop left to be planted. If the production objective is dry grain and you have been delayed, then you may want to begin pricing fuel for fall drying.

Other crops that night be grown can be found here.

Corn as an "emergency forage"

Corn planters could be brought back out after July 1. By this time, if fields are not planted, the production objective becomes "emergency forage" for dry matter production. We have produced up to 6.8 T/A dry matter with July planting dates for corn (see http://corn.agronomy.wisc.edu/Research/03DOP/Late2005.pdf and http://corn.agronomy.wisc.edu/Research/03DOP/Late2006.pdf).

Key Questions

1. What is the yield penalty for late-planted corn and soybean?
2. What are the latest recommended planting dates for corn?
3. What corn and soybean maturities should be used when planting late?
4. Should corn and soybean seeding rates change when planting is delayed?
5. Should corn and soybean planting depth change when planting is delayed?

Further Reading

Corn Replanting or Late-Planting Decisions (UWEX Bulletin A3353) for guidelines on switch dates for corn hybrid maturity.

Corn Planting Options for June June, 1996 Field Crops 28.421-7

Planting Corn in June and July! - What can you expect? June 2008 Field Crops 28.421-57 PDF/a>