Lebanon Crop Management Video

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28 April 2011

Spring Planting Delays when to begin making decisions

Del Voight - Senior Extension Agent - Penn State Extension

28, April 2011
We are experiencing probably the most difficult spring in years. As we move into May growers, that still have two weeks of manure spreading and alfalfa to harvest,  might find themselves planting much later than the  ideal planting dates for the area. Research suggests corn will begin decrease in yield after May 10 somewhere between 2-2.5 bu/day as the planting window narrows there will be some economic considerations that may be required to make rational decisions. These charts from the Agronomy Guide might come in handy.

Table 1.4-8. Estimated grain yields for various planting dates and population rates. Figures shown are most applicable to fields with less than 125 bushels per acre

Table 1.4-8. Estimated grain yields for various planting dates and population rates. Figures shown are most applicable to fields with less than 125 bushels per acre.
Planting datePlants/A at harvest
12,00014,00016,00018,00020,00022,50025,000
Optimum yield (percent)
April 2072788387909395
April 2575818690939698
May 1778388929598100
May 6788388929598100
May 1177838892959899
May 1675818690939698
May 2173788387919495
May 2669758084879092
May 3164707579828587
June 559646973778081
June 1052586367707375

Table 1.4-8B. Estimated grain yields for various planting dates and population rates

Table 1.4-8B. Estimated grain yields for various planting dates and population rates. Figures shown are most applicable to corn fields with yields greater than 175 bushels per acre.
Planting datePlants/A at harvest
10,00015,00020,00025,00030,00035,50040,000
Optimum yield (percent)
Source: University of Illinois
April 154687888959999
April 105770819197100100
April 20587181919710099
April 3058708089959796
May 955687786919391
May 1950637280858684
May 2944566573777875
June 835475663676764
This spread sheet will allow one to compare corn to soybean incomes. farmdocdaily: Planting Delays and Switching to Soybeans: A New FAST Spreadsheet

With Corn which is heat dependent growing degree days become important.  This chart details the latest planting dates based on a hybrid requiring 2600 heat units to develop. As the season progresses short season hybrids may need to be reviewed and used as necessary.

Soybeans do not lose yield at such a dramatic rate as corn however there are issues with switching. First off if any residual herbicides have been used the carryover can be an issue. Particularly for atrazine based products. ALS materials are another concern, however, there are STS varieties of soybeans that could work in that scenario.
In summary, it is too early to determine the best course of action as of today. It appears that in our area mid may returns to corn mimic soybeans however by the first week of June returns favor soybeans. More updates as this spring unfolds will be available through Extension research.

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