Abstract
Predictions of yield responses to planting date and plant population in corn ( Zea mays L.) are necessary in order to match plant population to a particular planting date, and also to make replant decisions. Much of the published research on these factors is relatively old. This study was conducted at Monmouth and DeKalb, Illinois for 4 yr (1987–1990) in order to formulate a predicted response of two modern hybrids to planting date and plant population. The two hybrids in the study showed no consistently different yield response to planting date, to plant population, or to the interaction of these two factors. Generally, yields increased from mid‐April to late April planting dates, then declined as planting was delayed to late May. Plant population had a very large effect on yield, except in the very dry environments at Monmouth in 1988 and 1989. The model found to give the best prediction of response to planting date and plant population was Yield (bu/acre) = 23.96 + 1.659D − 0.0303D 2 + 7.673P − 0.1266P 2 , where D = days after 1 April and P = plant population in thousands per acre. The population providing the highest yield was about 30 310 plants/acre, and the best planting time was found to be about 27 April. The table of predicted values from this study can be used to provide more accurate information on planting date and plant population responses of newer hybrids, and will be useful in making replant decisions when the initial planting is early enough to allow assessment of stand damage by mid‐May. Research Question It is essential that producers know how corn yields respond to planting date and plant population in order to optimize yields and to help make corn replanting decisions when stands are incomplete. There is a great need to update information on optimum planting date and plant populations using newer hybrids and management practices. Literature Summary The most widely used information about how corn hybrids respond to planting date and plant population was generated from research done about 15 yr ago, in which the first planting dates were late April or early May and the highest plant population used was 25 000 plants/acre. That study identified 6 May as the optimum planting date, and yields were still increasing at the highest plant population. A few other studies have been published in state extension bulletins and newsletters, but a recent review of this topic points out the lack of current information. Study Description Two corn hybrids—Pioneer Brand 3732 and Pioneer Brand 3615—were planted on four dates ranging from mid‐April to late May on a Drummer silty clay loam soil at DeKalb, IL, and on a Muscatine silt loam soil at Monmouth, IL, in each of the 4 yr 1987 to 1990. High levels of fertility were maintained throughout the study. Populations ranging from 10 000 to 35 000 plants/acre were established after emergence. Growing season moisture was adequate for good yields each year at DeKalb, but was deficient at Monmouth in 1988 and 1989. Applied Questions What are the best planting dates and plant populations for corn? The model developed from the results of this study showed the best planting date to be 27 April, and the best population for the two hybrids to be about 30 300 plants/acre. Yield losses accelerated as planting date moved earlier or later, or as plant population increased or declined from the optimum. Should plant population be changed according to the planting date? There was no interaction between planting date and plant population, meaning that final plant population should not be changed as planting date changes. If planting is delayed, however, seed rate should perhaps be decreased slightly in expectation of a higher percentage of the seeds emerging. Can we expect hybrids to differ in response to planting date and plant population? While we saw the two hybrids responding somewhat differently to planting date and plant population in the different environments, there was little consistency to these responses. How can these results be used to make replanting decisions? The following model was formulated based on the data from this study: Yield (% of maximum) = 14.71 + 1.018D − 0.0186D 2 + 4.709P − 0.07768P 2 Full scientific article from which this summary was written begins on page 59 of this issue. where D = number of days after 1 April and P = plant population in thousands per acre. This model was used to generate the following table: To use this table for replant decisions, simply assess the expected yield based on the original planting date and the present plant population, then see how much the yield would be increased if a full stand were re‐established by replanting on a given later date. If the difference in expected yield will return more money than the cost of replanting, then replanting should be considered. Costs arising from higher grain moisture at harvest and greater European corn borer damage should be added to the replanting cost. Our last planting dates were in late May, and this model should not be extended into June. Other work has shown, however, that yields decline very rapidly as planting is delayed into June, with expected losses as high as 50% if corn is planted in mid‐June. Plant population, thousands per acre Date 10 15 20 25 30 35 ‐‐‐‐‐‐‐‐‐‐‐‐ % of maximum yield ‐‐‐‐‐‐‐‐‐‐‐‐ 10 Apr. 62 76 86 92 94 93 20 Apr. 67 81 91 97 99 97 30 Apr. 68 82 92 98 100 98 9 May 65 79 89 95 97 96 19 May 59 73 83 89 91 89 29 May 49 63 73 79 81 79
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Claims 16
Claim · model-written summary
The two hybrids showed no consistent difference in yield response to planting date, plant population, or their interaction.
- Taxon
- corn
Zea mays subsp. mayst0 - Material
- two hybridse0
- Outcome
- yield responsee0
- Direction
- no consistently differente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“The two hybrids in the study showed no consistently different yield response to planting date, to plant population, or to the interaction of these two factors.”
Claim · model-written summary
Yield increased from mid-April to late-April planting.
- Taxon
- cornZea mays subsp. mayst0
- Treatment
- late April planting datese0
- Outcome
- yieldse0
- Direction
- increasede0
- Comparator
- mid‐Aprile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“Generally, yields increased from mid‐April to late April planting dates”
Claim · model-written summary
Yield declined with planting delayed to late May.
- Taxon
- cornZea mays subsp. mayst0
- Treatment
- planting was delayed to late Maye0
- Outcome
- declinede0
- Direction
- declinede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“then declined as planting was delayed to late May”
Claim · model-written summary
Population had a very large effect on yield except in very dry Monmouth environments in 1988 and 1989.
- Taxon
- cornZea mays subsp. mayst0
- Treatment
- Plant populatione0
- Outcome
- yielde0
- Qualifier
- except in the very dry environments at Monmouth in 1988 and 1989e0
- Setting
- Monmouthe0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“Plant population had a very large effect on yield, except in the very dry environments at Monmouth in 1988 and 1989.”
Claim · model-written summary
A quadratic model gave the best prediction of yield response to planting date and population.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- best prediction of response to planting date and plant populatione0
- Direction
- beste0
- Comparator
- The modele0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“The model found to give the best prediction of response to planting date and plant population was Yield (bu/acre) = 23.96 + 1.659D − 0.0303D 2 + 7.673P − 0.1266P 2”
Claim · model-written summary
The highest-yielding population was about 30 310 plants/acre.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- highest yielde0
- Direction
- higheste0
- Value
- about 30 310 plants/acree0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“The population providing the highest yield was about 30 310 plants/acre”
Claim · model-written summary
The best planting time was about 27 April.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- best planting timee0
- Direction
- beste0
- Value
- about 27 Aprile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“the best planting time was found to be about 27 April”
Claim · model-written summary
Yield losses accelerated as dates moved earlier or later than optimum.
- Taxon
- cornZea mays subsp. mayst0
- Treatment
- planting date moved earlier or latere0
- Outcome
- Yield lossese0
- Direction
- acceleratede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“Yield losses accelerated as planting date moved earlier or later”
Claim · model-written summary
Yield losses accelerated as population increased or declined from optimum.
- Taxon
- cornZea mays subsp. mayst0
- Treatment
- plant population increased or declinede0
- Outcome
- plant populatione0
- Comparator
- the optimume0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“as plant population increased or declined from the optimum”
Claim · model-written summary
There was no interaction between planting date and plant population.
- Taxon
- cornZea mays subsp. mayst0
- Treatment
- planting datee0
- Outcome
- interaction between planting date and plant populatione0
- Direction
- no interactione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“There was no interaction between planting date and plant population”
Claim · model-written summary
The authors advise keeping final plant population unchanged across planting dates.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- final plant population should not be changed as planting date changese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“final plant population should not be changed as planting date changes”
Claim · model-written summary
The authors suggest slightly decreasing seed rate if planting is delayed.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- seed rate should perhaps be decreased slightlye0
- Qualifier
- If planting is delayede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“If planting is delayed, however, seed rate should perhaps be decreased slightly in expectation of a higher percentage of the seeds emerging.”
Claim · model-written summary
The study formulated a percentage-of-maximum-yield model for replant decisions.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- Yield (% of maximum)e0
- Value
- 14.71 + 1.018D − 0.0186D 2 + 4.709P − 0.07768P 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“Yield (% of maximum) = 14.71 + 1.018D − 0.0186D 2 + 4.709P − 0.07768P 2”
Claim · model-written summary
The authors recommend replanting when expected yield gain exceeds replanting cost.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- replanting should be considerede0
- Qualifier
- If the difference in expected yield will return more money than the cost of replantinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“If the difference in expected yield will return more money than the cost of replanting, then replanting should be considered.”
Claim · model-written summary
The authors recommend including grain moisture and corn borer damage costs in replanting cost.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- should be added to the replanting coste0
- Qualifier
- Costs arising from higher grain moisture at harvest and greater European corn borer damagee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“Costs arising from higher grain moisture at harvest and greater European corn borer damage should be added to the replanting cost.”
Claim · model-written summary
The authors advise against extending the model into June.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- this model should not be extended into Junee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Corn”
e0“this model should not be extended into June”
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