AgAlerts 2004 From Griggs County
By John Swenson, Griggs County Extension Agent

Issue # 9, August 18, 2004

Late Maturing Corn

    The question of the day is "will this corn make it".  Several factors will play a role in answering this question.  Joel Ransom, NDSU Extension Cereal Agronomist, has put together some information that addresses this issue.

WILL CORN MATURE IN 2004?

The 2004 growing season will no doubt go down in the record books as one of the coldest in recent years. Due to the unusually cold weather, the development of the 1.85 million acres (also a record) of corn planted this year is way behind average. The question of the day is, "will corn mature this year?" The answer to that question depends on a number of factors such as when and where the crop was planted, the RM of the hybrid used and how many growing degree days we accumulate between now and the first killing frost. Given that the high today (Aug 10th) will probably be about the same as the long-term average low for the month, the prospects of a delayed crop being pushed by warm weather to the finish are rapidly diminishing. So what are the prospects for the current corn crop in ND?

As I reviewed the available literature, it became apparent that given the diversity of environments and hybrids used in the state, developing a broadly applicable prognosis on how corn will finish this season would not be possible. So in this article I will describe some principles and provide some numbers that will hopefully allow you to make a reasonable predication as to how your corn might fair this year.

Corn growth and development can be fairly closely predicted using growing degree day accumulations. A 75 RM hybrid, for example needs about 1900 GDD from planting to reach physiological maturity, while a 95 RM hybrid requires about 2300 GDD. Much of the difference in GDD requirements between early and late maturing hybrids is related to the number of days from planting to silking and less so in the number of days from silking to physiological maturity. Therefore, the silking date is a useful reference point to start from when evaluating how your current crop might finish.

In general terms, corn hybrids adapted to ND require between 900-1100 GDDs from silking to reach physiological maturity (black layer) or about 55 to 60 calendar days. Some data suggest that the number of calendar days and not just GDDs play an important role in correctly predicting grain development (Lauer, 2004), so both GDD and calendar days will be considered here. Table 1 summarizes the GGD accumulations and date of first killing frost (30 degrees or less) for selected locations in the state for the past five years assuming a August 1 silking date (about half of the corn in ND was reported to have silked by 1 August). I should also point out that we have to be a bit caution in using these data to predict how things will happen this year as GDD accumulations this year to date are significantly less than those of the past five year. Having said that, these GDD accumulations for the past five years suggest that only corn that flowered on or before August 1 in locations with GDD like Fargo (i.e. those further south) has a reasonable chance of reaching physiological maturity. Days from August 1 to the first killing frost varied over the past 5 years and locations from about 50 to 65, suggesting a slightly more optimistic scenario for corn development than GDDs alone (i.e. in most locations and season there are at least 55 days from 1 August to the first killing frost).

For corn crops that will not reach physiological maturity based on the analysis described in the previous paragraph, Table 2 summarizes the GDDs needed to reach various stages of kernel development and the associated moisture content of those stages. As an example of how you might use this table, if we use just GDDs, a corn crop that silked on August 1st in Langdon will receive on average (average of the 5 most recent growing season) only 713 GDDs from August 1 until the first killing frost. This is less than the 900 GDDs needed for the crop to reach physiological maturity and just slightly more than the 700 required for the crop to reach the early dent stage. At this stage(early dent), the moisture content in the grain will be about 50% and the yield potential will be reduced by about 40% (Table 2). Hopefully combining the information on the likely number of GDDs (in Table 1) that will accumulate near your farm with the information on the number of GDDs needed for kernels to develop (Table 2) will allow you to make a fairly good prediction of how your crop might finish.

Summary and recommendations:

Due to the unusually cool growing season, corn development in most of the state is far behind the average for this time of the year. Based on the available data it appears probable that fields that were planted early with an adapted hybrid in the southeastern part of the state (that silked on or before August 1) will likely reach physiological maturity, but will have higher than average moisture at harvest. Fields that silked on or before August 1 in the central region of the state and those that silked after 1 August in the southeastern region of the state will probably not reach physiological maturity by the first frost and will probably be difficult to combine without exceptionally favorable field drying conditions. Yield losses will be modest and test weights will be light. Corn in the central and northern regions of the state that silked after August 1st (particularly those that silked after the first week of August) will likely only reach the dent stage of development. Corn in the early dent stage at the time of the first frost will produce light grain that may be difficult to harvest even after several weeks of field drying. If it appears that your corn crop will only make the early dent stage, you should carefully consider some of the alternative uses of corn. 

Table 1. Corn growing degree day (GDD) accumulations from August 1st to the first killing frost (30B or less) and date of the first killing frost for selected locations in North Dakota, 1999-2003.

Location

 

1999

2000

2001

2002

2003

Ave

GDD

Frost Date

GDD

Frost Date

GDD

Frost Date

GDD

Frost Date

GDD

Frost Date

GDD

Carrington

702

9/30

727

9/23

802

9/24

829

10/2

853

9/24

783

Fargo

820

10/1

936

10/4

1,000

10/5

1,019

10/9

1,124

9/30

980

Langdon

573

9/20

646

9/23

824

10/5

721

9/25

801

9/24

713

Minot

718

9/30

735

9/23

919

10/4

896

9/25

871

9/19

828

Table 2. Growing degree or calendar days required from silking for the corn plant to reach the indicated stage, moisture content of the grain and potential yield loss after a killing frost at the indicated growth stage (adapted from Jones and Andersen, 1997; and Lauer, 2004,).

 

GGD1

Calendar days

% Grain moisture

% loss after a killing frost

Early dent

700-850

38

50-55

40

Half milk

800-1000

49

35-40

12

Black layer

900-1100

60

30-35

0

1- This range of values applies to hybrids between 75 and 95 RM with the smaller number corresponding to the earliest hybrids and the larger number to later maturing hybrids. Since earlier maturing hybrids tend to be grown in regions of the state where GDDs are accumulated more slowly than regions where later hybrids are grown, the calendar day requirements for early and late hybrids grown in locations of the state where they are adapted are about the same.

Current GDD for Dazey and McHenry weather stations are as follows:

                        GDD from 5/1-8-17    GDD from 8/1-8-17
Dazey                      1256                            201  
McHenry                  1236                            202

To look at current GDD at any NDAWN station click on the following: http://www.ndawn.ndsu.nodak.edu/corndd-form.html

References

Jones, M. And J. Anderson. 1997. Delayed maturity in 1997 - Potential frost damage and other effects in corn. http://www.ipm.msu.edu/delayed.htm.

Lauer, J. 2004 projected 2004 corn harvest dates for silage and grain.Wisconsin Crop Manager 11(20):132_133. (http://corn.agronomy.wisc.edu/WCM/2004/W154.htm).


Post-Harvest Tips for Late Maturing Corn

Following is an article on Post-Harvest Tips for Late Maturing Corn. I have provided brief guidance on a number of issues that may surface this year. You may also refer to my Crop Post Harvest web site for an extensive amount of information. http://www.ag.ndsu.nodak.edu/abeng/postharvest.htm
Ken Hellevang
Ph.D., PE, Extension Engineer, Professor
 
    Yield potential for corn frozen during the milk stage is low. Ears are difficult to pick and shell, kernel tips may stay on the cobs, and grain will be very chaffy. Therefore, green chopping or ensiling whole plants may be the only reasonable options. Corn silage should be harvested at 60 to 70% moisture. The length of cut should be about 0.5 inch long with not more than 10 to 15% being 1 inch or longer. A bunker or horizontal silo should be crowned in the center, have a wall slope of 1:6 to 1:8, and be covered with 6 mil polyethylene. To be effective the plastic must be held down over its entire area. Temperatures above 120 degrees after 4 days indicates that excess air is getting into the silage.
    Test weights will be much less, probably 40 to 45 lb/bu., for corn frozen in the dough stage. Although corn will eventually dry to an acceptable harvest moisture, it will take at least a week longer than mature grain. During the extended drying period, field losses due to stalk breakage and ear dropping will increase. Ear molds will likely develop if warm ambient temperatures follow the frost. The only means of stopping mold growth are drying the grain or ensiling.
    Standing corn in the field may dry 0.75 to 1.0 percentage point per day during warm, dry fall days with a breeze. Normally about one-half percent per day is expected in North Dakota. Immature, frosted corn can mold on the stalk.
    A hard freeze in the dent stage will result in shrivelled kernels with lower test weight.
    Shelled corn can be stored in a grain bin at moisture contents up to about 25% if it is kept below 30 degrees using aeration. Shelled corn should be at 25 to 30% moisture for anaerobic (without oxygen) high moisture storage in silos or silo bags. Any tears in the plastic bag must be promptly repaired to minimize storage losses. Whole shelled corn can be stored in oxygen-limiting silos, but a medium grind is needed for proper packing in horizontal or conventional upright silos. Wet grain exerts more pressure on the silo than corn silage, so conventional concrete stave silos may require additional hoops or the silo must not be completely filled.
    The desired moisture content for safe cribbing of ear corn is 20% or less. Late in the season when temperatures are consistently near or below freezing, ear corn can be cribbed at moisture contents of 22 to 25%. Crib width of 6 to 9 feet can be used for 20% moisture or less and widths of 4 to 5 feet for 20 to 25% moisture corn. The importance of clean husking cannot be over- emphasized, since the husks greatly reduce airflow through the crib. Locate corncribs away from buildings in a well-drained area oriented with the side facing the prevailing wind.
    Dryers will be operated more hours than usual, so examine them carefully and perform needed maintenance before harvest. Use the maximum allowable drying temperature in a high temperature dryer to increase dryer capacity and energy efficiency. Be aware that high drying temperatures result in a lower final test weight and increased breakage susceptibility. Use in-storage cooling instead of in-dryer cooling to reduce fuel use and boost capacity of high- temperature dryers. Cooling corn slowly in a bin rather than in the high temperature dryer will also reduce the potential for stress cracks in the kernels.
    As the drying time increases with high moisture corn, it becomes more susceptible to browning. Research indicates that exposure to drying air temperatures above 200 degrees for time periods in excess of 2 hours will likely result in some degree of browning. For corn above 30% moisture, browning is likely to occur. Dryer temperatures may need to be limited to less than 160 degrees to prevent scorching or browning.
    In-storage cooling requires a positive-pressure, aeration, airflow rate of about 0.20 cfm/bu or 12 cfm/bu-hr of fill rate. Cooling should be started immediately when corn is placed in the bin from the dryer. Dryer capacity is increased 20 to 40% and about one percentage point of moisture is removed during corn cooling. 
    Dryeration will increase the dryer capacity about 50 to 75% and remove about 2 to 2.5 points of moisture. (0.25% for each 10 degrees the corn is cooled.) With dryeration, hot corn from the dryer is placed in a dryeration bin with a perforated floor, allowed to steep for 4 to 6 hours without airflow, cooled, and then moved to a storage bin. There will be a tremendous amount of condensation during the steeping and cooling process, so the corn must be moved to a different bin for storage or spoilage will occur along the bin wall and on the top grain surface.
    Combination drying greatly increases the drying capacity of a high temperature dryer, saves gas, and improves corn quality. Combination drying is the process of using a high temperature dryer to dry the corn to about 20 to 22% moisture, placing the corn hot in a natural air drying bin, and then completing drying with an airflow rate of at least 1.0 cfm/bu.
    Natural air and low temperature drying should be completed as much as possible in October because the drying capacity is extremely poor during the colder temperatures in November. Corn above 21% moisture should not be dried using natural air and low temperature drying to minimize corn spoilage during drying. An airflow rate of 1.25 cfm/bu is recommended to reduce drying time. Adding heat does not permit drying wetter corn and only slightly increases drying speed. The primary effect of adding heat is to reduce the corn moisture content.
    Energy cost for high temperature drying corn will be about  $0.013 per bushel per point of moisture removed using $0.50 per gallon propane, $0.016 for $0.70 propane, and $0.023 for $0.90 propane. Total drying cost includes capital and fixed costs such as depreciation, repairs, insurance, and etc. This cost will vary depending on dryer cost and the amount of grain dried. This might be $0.10 to $0.15 per bushel. It costs about $8.00 for energy to remove 5 percentage points of moisture from 100 bushels of corn using $0.70 propane. This is equivalent to a field loss of 3.5 bushels if corn is $2.25 per bushel.
    Moisture shrink is the reduction in weight as the grain is dried one percentage point. Moisture Shrink Factor = 100 ¸ (100 – final moisture content). The shrink factor drying corn to 15.5% is 1.1834. The shrink drying corn from 20.5 to 15.5 would be 5 x 1.1834 = 5.92%.
    Moisture meters will not provide accurate readings on corn coming from a high temperature dryer. The error will vary depending on the amount of moisture removed and the drying temperature, but the meter reading may be about 2% lower than true moisture. Check the moisture of a sample, place the sample in a closed container for about 12 hours, and then check the moisture content again to determine the amount of error. Moisture meter errors increase as corn moisture contents increase, so readings above 25% should only be considered estimates.
    A few wet loads can lead to spoilage in storage or in natural air & low temperature drying bins. Measure the moisture of every load going into and out of a dryer and into storage.
    Normally, corn test weight increases about 0.25 pound for each point of moisture removal during high temperature drying. However, there will be little increase in test weight on immature or frost-damaged corn.
    More fines are produced when corn is wet, because more aggressive shelling is required, which causes more kernel cracking and breaking. There is also more potential for stress cracks in kernels during drying, which leads to more breakage potential during handling. In addition, immature corn contains more small and shriveled kernels.  Fines cause storage problems because they spoil faster than whole kernels, they have high airflow resistance, and they accumulate in high concentrations under the fill hole unless a spreader or distributor is used. Preferably, the corn should be screen-cleaned before binning to remove fine material, cob pieces, and broken kernels.
    Immature corn has a shorter storage life than mature corn. Therefore, cooling the grain in storage to about 20 to 25 degrees for winter storage is more important than for mature corn. More frequent checking of the storage is recommended, and immature corn is not recommended for long-term storage. Corn kernels above about 25% moisture may freeze into a clump that causes unloading problems.

Please Contact Our Office For Additional Information
E-mail: john.swenson@ndsu.edu
Go to the 2003 AgAlert Index Page