Delayed Planting Effects on Corn Yield: A “Historical” Perspective

Delayed Planting Effects on Corn Yield: A “Historical” Perspective
May 07, 2019

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By Allen Geyer and Peter Thomison

According to the USDA/NASS, for the week ending May 5, only 2% of Ohio’s projected corn acreage was planted - compared to 20% last year and 27% for the five-year average. Persistent rains and saturated soil conditions have delayed corn planting. The weather forecast this week indicates the likelihood of more rain, so it is probable that many soggy fields may not dry out soon.
 
Long-term research by universities and seed companies across the Corn Belt gives us a pretty good idea of planting date effects on relative yield potential. The recommended time for planting corn in northern Ohio is April 15 to May 10 and in southern Ohio, April 10 to May 10. In the central Corn Belt, estimated yield loss per day with delayed planting varies from about 0.3% per day early in May to about 1% per day by the end of May (Nielsen, 2019). These yield losses can be attributed to a number of factors including a shorter growing season, greater disease and insect pressure and higher risk of hot, dry conditions during pollination.
 
Given these planting date effects, do yield losses associated with late plantings translate into lower statewide yields? Not necessarily. Let’s consider some previous growing seasons that were characterized by a “late start” and what impact this had on crop production. For the purposes of this discussion, we will consider “late start” years as those in which 40% or more of the corn acreage was not planted by May 20. Since 1980, there have been significant planting delays associated with wet spring weather in eleven years – 1981, 1983, 1989, 1995, 1996, 2002, 2008, 2009, 2011, 2014 and 2016. 
 
Table 1 shows the percentage of corn acreage planted by May 20 and May 30, the 50% planting date (the date by which 50% of the corn acreage was planted), yield, the state average yield for the previous five years, and the departure from the yield trend in each of those years. Of these eleven years, the greatest delays in crop planting occurred in 2011 when only 19% of the corn acreage was planted by May 30. In five of the eleven years (1981, 1983, 1996, 2002, and 2008) average state yields were markedly lower than the state average yield of the previous five years (In six of the eleven years, average yields were five bushels per acre or more below the yield trend line for Ohio). In one of these years, 2002, the average corn yield dropped to 89 bushels per acre (nearly comparable to the record low of 86 bushels per acre for the major drought year of 1988). However, in six of the eleven years, yields were similar or higher than the statewide average yield of the previous five years, and in one of these years, 2014, a record high corn yield, 176 per acre, was achieved.
 
In 2017, 73% of the corn crop was planted by May 20 (which does not categorize 2017 as having a “late start”).  However, field agronomists and county ag extension educators estimated that as much as 40% or more of the corn planted in late April of 2017 was replanted in parts of Ohio due to excessive soil moisture, freezing temperatures and frosts, fungal seed decay and seedling rots, and soil crusting. (NASS does not report replanted corn.) Nevertheless, the yield in 2017 was a record 177 bushels per acre, 16 bushels above the yield trend. 
 
Table 1.  Performance of Ohio’s “Late” Planted Corn Crop – Yield
 

 

% of Crop Planted by

 

 

 

 

 

 

Year

 

 

May 20

 

 

May 30

 

50%

Planting Date

 

Yield (Bu/A)

 

Avg. Yield of

Previous 5 Years

Departure from Yield Trend (Bu/A)

 

1981

 

30

 

55

 

May 26

 

96

 

108

 

-10

 

1983

 

45

 

65

 

May 22

 

80

 

109

 

-29

 

1989

 

22

 

40

 

June 4

 

118

 

116

 

0

 

1995

 

60

 

77

 

May 19

 

121

 

122

 

-6

 

1996

 

10

 

54

 

June 1

 

111

 

122

 

-17

 

2002

 

22

 

58

 

May 28

 

89

 

138

 

-48

 

2008

 

50

 

66

 

May 20

 

131

 

153

 

-14

 

2009

 

42

 

95

 

May 22

 

171

 

149

 

24

 

2011

 

10

 

19

 

June 5

 

153

 

153

 

2

 

2014

 

50

 

85

 

May 20

 

176

 

156

 

20

 

2016

 

50

 

84

 

May 20

 

159

 

155

 

0

 
This comparison of statewide average corn yields from past years (Table 1) indicates that lower grain yields are not a certainty with late plantings. While delayed planting may cause yield loss relative to early planting, planting date is just one of many factors that influence corn yield. Figure 1 shows grain yields associated with dates by which 50% of the corn acreage was planted in Ohio from 1980 to 2018 and it does not suggest a strong relationship between planting date and yield. There are other factors that are of greater importance than planting date in determining grain yield. Weather conditions (rainfall and temperature) in July and August are probably the most important yield determining factors. Favorable weather conditions subsequent to planting may result in late planted crops producing above average yields as was case in 2009 and 2014. However, if late planted crops experience severe moisture stress during pollination and grainfill, then crop yields may be significantly lower than average, with 2002 being the most notable example.  
 
Figure 1.  Corn yields associated with 50% planting dates, Ohio, 1980-2018.