Phantom Yield Loss in Corn - A Five-Year Nebraska Field Study

Agronomy Research Update
From Pioneer Agronomy Sciences

Key Findings

It is not uncommon to observe lower yield in a portion of a corn field harvested later than the rest, a phenomenon commonly referred to as phantom yield loss.
Yield declined by an average of 9.1 bu/acre with later harvest in a 5-year study in south-central Nebraska.
Neither the change in grain moisture nor the duration of time between earlier and later harvest had any relationship with the difference in yield.

Jump to: Lower Yields Observed with Later Harvest Study Description Results Discussion References

Lower Yields Observed with Later Harvest

When harvest is delayed due to weather or other factors, it is not uncommon to observe lower yields in the portion of the field harvested later than the portion harvested earlier, a phenomenon commonly referred to as mystery yield loss or phantom yield loss.
There are a number of possible reasons why yield may decline or appear to decline with later harvest, including ear drop, stalk lodging, insect feeding, ear rots, harvest loss, and inaccurate yield monitor calibration.
Dry matter loss resulting from kernel respiration during grain dry down has also been hypothesized as an explanation for lower yields with later harvest dates.
- However, research on kernel respiration rates does not appear to support this hypothesis as a plausible mechanism for the differences in yield being observed in some cases (Knittle and Burris, 1976; Saul and Steele, 1966).
- Several Pioneer and university studies have shown no evidence of kernel dry matter loss following physiological maturity (Cerwick and Cavalieri, 1984; Elmore and Roeth, 1996; Licht et al, 2017; Reese and Jones, 1995; Thomison, et al, 2011).

A Pioneer Agronomy study conducted in 2018 examined the role of harvest loss in differences in yield between earlier and later harvest timings (Leusink and Jeschke, 2019).
- Yield declined by an average of 8.9 bu/acre with later harvest in this study.
- Trial locations varied widely in the difference in grain moisture and the number of days between the two harvest timings, neither of which correlated with observed differences in yield.
- Greater harvest losses were observed with grain moisture levels below 19%; however, measured harvest losses (ears and kernels on the ground) did not fully account for the differences in yield.

Corn stalks - with mature ears - harvest season

Study Description

A study comparing corn yield between earlier and later harvest timings was conducted over 5 years in south-central Nebraska.
At each study location, yield was compared between a portion of the field harvested relatively early and proximal portion of the field planted to the same hybrid harvested later in the fall.
A total of 34 comparisons were made over the five years of the study, including 11 in 2018, 8 in 2019, 8 in 2020, 6 in 2021, and 2 in 2022.
Comparisons included 18 different hybrids ranging from 105 to 118 CRM. Ten of the comparisons were in dryland production and 24 were irrigated.
Grain moisture at the earlier harvest timing averaged 20.7% across locations with a range of 15.3% to 25.3%.
Grain moisture at the later harvest timing averaged 16.9% across locations with a range of 12.9% to 20.6%.

Results

Yield declined by an average of 9.1 bu/acre with later harvest in this study (Table 1); a result very similar to the 8.9 bu/acre average decline observed in the 2018 Pioneer Agronomy study.
Yield differences between harvest timings ranged from a decrease of 29.9 bu/acre with later harvest to an increase of 2.2 bu/acre (Table 1).
There were no factors that seemed to correlate with or predict yield difference between earlier and later harvest.
- Neither the change in grain moisture nor the duration of time between earlier and later harvest had any relationship with the difference in yield (Figure 1).
- Grain moisture at the later harvest timing had no apparent relationship with the difference in yield either, even though greater harvest losses would be expected as moisture dropped below 19%.
- Calendar date of the earlier and later harvest timings also seemed to have no impact on yield loss.

Table 1. Harvest date, grain moisture and yield of early and late harvest timings for 34 comparisons over five years.

	Harvest Date		Grain Moisture (%)		Yield (bu/acre)		Difference
Year	Early	Late	Early	Late	Early	Late	Days	Moisture	Yield
2018	Sept 17	Sept 23	23.1	19.1	231.1	220.5	6	4.0	10.6
	Sept 20	Sept 28	19.7	17.5	213.1	210.4	8	2.2	2.7
	Sept 20	Sept 28	19.9	18.0	232.1	221.4	8	1.9	10.7
	Sept 20	Sept 28	20.1	18.0	243.7	238.4	8	2.1	5.3
	Sept 20	Oct 25	19.6	14.0	260.4	261.2	35	5.6	+0.8
	Sept 23	Sept 26	19.1	17.9	220.5	210.2	3	1.2	10.3
	Sept 24	Oct 16	15.9	15.3	162.1	155.8	22	0.6	6.3
	Sept 25	Oct 17	20.4	19.2	271.2	264.7	22	1.2	6.5
	Sept 25	Oct 15	21.1	15.1	269.5	248.4	20	6.0	21.1
	Oct 2	Oct 24	21.6	16.4	290.5	280.3	22	5.2	10.2
	Oct 16	Oct 27	15.3	15.0	155.8	154.3	11	0.3	1.5

	Harvest Date		Grain Moisture (%)		Yield (bu/acre)		Difference
Year	Early	Late	Early	Late	Early	Late	Days	Moisture	Yield
2019	Sept 18	Oct 15	23.4	16.5	255.8	229.1	27	6.9	26.7
	Sept 19	Oct 15	25.3	15.0	203.8	197.9	26	10.3	5.9
	Sept 25	Oct 12	20.0	16.9	230.5	221.4	17	3.1	9.1
	Sept 27	Oct 13	20.9	19.3	236.5	229.7	16	1.6	6.8
	Sept 27	Oct 12	23.5	20.2	250.3	241.4	15	3.3	8.9
	Sept 30	Oct 23	24.0	16.6	264.7	249.9	23	7.4	14.8
	Oct 7	Oct 15	20.2	17.0	193.1	184.0	8	3.2	9.1
	Oct 7	Oct 15	21.5	16.5	192.5	183.6	8	5.0	8.9

	Harvest Date		Grain Moisture (%)		Yield (bu/acre)		Difference
Year	Early	Late	Early	Late	Early	Late	Days	Moisture	Yield
2020	Sept 23	Oct 2	22.4	17.0	225.9	196.0	9	5.4	29.9
	Sept 24	Oct 1	23.9	17.8	270.6	266.3	7	6.1	4.3
	Sept 25	Sept 30	20.5	18.9	234.5	226.2	5	1.6	8.3
	Sept 28	Oct 13	21.5	17.0	244.6	229.9	15	4.5	14.7
	Sept 28	Oct 6	24.4	20.6	255.3	246.6	8	3.8	8.7
	Oct 1	Oct 9	19.7	15.9	284.9	280.6	8	3.8	4.3
	Oct 3	Oct 17	17.8	13.4	266.3	253.1	14	4.4	13.2

	Harvest Date		Grain Moisture (%)		Yield (bu/acre)		Difference
Year	Early	Late	Early	Late	Early	Late	Days	Moisture	Yield
2021	Sept 20	Oct 10	19.8	18.6	217.9	211.3	20	1.2	6.6
	Sept 27	Oct 10	19	15	220.8	210.8	13	4.0	10.0
	Sept 29-	Oct 22	19.8	14.7	265.3	267.5	23	5.1	+2.2
	Sept 29	Oct 22	18.4	12.9	253.5	251	23	5.5	2.5
	Oct 2	Oct 12	20	17.2	269.6	261.2	10	2.8	8.4
	Oct 2	Oct 12	22	18.7	259.4	254.7	10	3.3	4.7

	Harvest Date		Grain Moisture (%)		Yield (bu/acre)		Difference
Year	Early	Late	Early	Late	Early	Late	Days	Moisture	Yield
2022	Sept 27	Oct 10	23.1	17	214.3	206.8	13	6.1	7.5
	Oct 6	Oct 10	17	15.2	220.8	207.9	4	1.8	12.9

Discussion

Results of this study corresponded with those of previous studies and grower observations that corn yield often declines with later harvest.
However, neither the change in grain moisture nor the length of additional time in the field seemed to have any effect on the observed decrease in yield.
The 2018 Pioneer Agronomy study showed an increase in harvest loss as grain moisture at harvest declined and suggested the possibility that additional unmeasured harvest loss may have contributed to observed declines in yield.

Yield loss with later harvest as a function of grain moisture loss and additional days of field drying.

Figure 1. Yield loss with later harvest as a function of grain moisture loss (left) and additional days of field drying (right) showing no correlation to either factor.

The 2018 study measured ear drop and whole kernels on the ground after harvest; any kernels lost through breakage before or during harvest would not have been quantified.
A higher rate of ear molds and stress cracks as corn dries down in the field could lead to higher rates of kernel breakage during harvest.
Harvest loss was not quantified in this study; however, observations at multiple locations were suggestive of greater harvest losses with later harvest (Figure 2, Figure 3, Figure 4, Figure 5, Figure 6 and Figure 7).

Compromised kernel integrity due to ear or kernel mold.

Figure 2. Compromised kernel integrity due to ear or kernel mold.

Broken kernel particles blown out the back of a combine.

Figure 3. “Fines” – broken kernel particles blown out the back of the combine. Plot was harvested November 4th at 16% moisture.

Cob shrink causing corn kernels to fall out.

Figure 4. 'Cob shrink’ causing kernels to fall out.

Stress cracks on corn kernels that can lead to more fines.

Figure 5. Stress cracks that can lead to more fines.

Kernels on the ground from shelling at the combine head.

Figure 6. Kernels on the ground from shelling at the head.

Accumulated grain dust from pulverized kernels in a corn field infested with Fusarium ear rot.

Figure 7. Accumulated grain dust from pulverized kernels in a field infested with Fusarium ear rot.

References

Cerwick, S.F.., and A.J. Cavalieri. 1984. Unpublished. Pioneer Hi-Bred International, Inc. Johnston, IA.
Elmore, R.W., and W.F. Roeth. 1999. Corn kernel weight and grain yield stability during post-maturity drydown. J. Prod. Agric. 12:300-305.
Knittle, K.H. and J.S. Burris. 1976. Effect of kernel maturation on subsequent seedling vigor in maize. Crop Sci. 16:851-855.
Leusink, S. and M. Jeschke. 2019. Harvest Timing Effect on Corn Yield. Pioneer Agronomy Research Update. Vol. 9 No. 1. Corteva Agriscience Johnston, IA.
Licht, M., C. Hurburgh, M. Kots, P. Blake and M. Hanna. 2017. Is there loss of corn dry matter in the field after maturity? In Proceedings of the 29th Annual Integrated Crop Management Conference, Iowa State University, Ames, Iowa.
Reese, K.D., and G. Jones. 1996. Unpublished. Pioneer, Johnston, Iowa.
Saul, R.A., and J.L. Steele, 1966. Why damaged shelled corn costs more to dry. Agric. Eng. 47:326-329.
Thomison, P.R., R.W. Mullen, P.E. Lipps, T.A. Doerge, and A.B. Geyer. 2011. Corn response to harvest date as affected by plant population and hybrid. Agron. J. 103:1765–1772.

The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. 2018-2022 data are based on average of all comparisons made in 34 locations through Nov. 1, 2022. Multi-year and multi-location is a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection. Product responses are variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary.

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