Will Corn Mature Before Frost?

The following article is a summary of a field day presentation for the Dodge/Fond du Lac County Corn Growers Association on July 24 at Lamartine, WI.  PDF. 

During cool growing seasons, especially when planting is delayed due to wet spring conditions, growers are concerned about whether their corn is vulnerable and will reach maturity before normal frost dates. Often the range in planting dates have implications at harvest time, especially for silage because grain and dairy producers often negotiate the sale of corn in fields that are borderline for development.

Most hybrids require about 55 to 60 days to develop from the silk stage to physiological maturity. Hybrid maturity differences in development time occur primarily from emergence to silking, not from silking to maturity.

Most concern exists when corn does not reach the silk stage (R1) until early August or later. Killing frosts can easily occur by late September, so corn silking in early August would not be safe from major yield reductions due to frost until early October.

Figures 1 and 2 describe typical development of corn silage yield and quality and of a corn kernel. At the dent stage (R5), corn has accumulated 75-85% of silage yield and 60-75% of grain yield and needs about 27-32 days to avoid significant yield reductions due to frost (Table 1). In order to avoid yield reductions caused by frost, corn intended for silage should be silking by late August, while corn intended for dry grain should reach the dent stage by September 1.

Figure 1. Corn silage yield and quality changes during development.

Figure 2. Typical corn kernel development in Wisconsin.

Table 1. The relationship between kernel growth stage and development.

Stage	Calendar days to maturity	GDUs to maturity	Percent of maximum yield  Grain                Silage		Moisture content (%) Grain                Silage
R1: Silking	55-60	1100-1200	0	45-50	---	80-85
R2: Blister	45-50	875-975	0-10	55-60	85-95	80-85
R3: Milk	35-40	750-850	10-30	60-65	70-85	80-85
R4: Dough	30-35	650-750	30-60	65-75	60-70	75-80
R5: Dent	27-32	425-525	60-75	75-85	50-55	70-75
R5.5: 50% Kernel milk	13-18	200-300	90-95	100	35-40	65-70
R6: Black layer	0	0	100	95-100	30-35	55-65

To predict whether corn will mature before frost note the hybrid maturity, planting date and tasseling (silking) date of the field. For silage, add 42-47 days on to this date to predict 50% kernel milk, while for grain, add 55-60 days to predict maturity. These dates are guidelines which will require further in-season decisions as the season unfolds.

Corn Production in the Northern Corn Belt: The Tillage X Rotation Interaction

The following article is a summary of a field day presentation for the Conservation Cropping Systems Project on July 18 at Forman, ND.  PDF. 

The corn-soybean rotation has become dominant in the Corn Belt of the U.S in the last 30-40 years. When compared to other systems like the wheat system of the Middle East and the rice systems of the Far East that have been in place for centuries, it is a relatively new cropping system. Many agronomists are concerned about the sustainability of this system and there is some evidence that with the development of resistant weeds and insects that it might be challenged significantly in the near future.

Figure 1. How can you tell if a cropping system is changing?

The objective of this study was to measure the response of tillage in a rotation trial that has increasing amounts of continuous corn. The experimental unit is the plot of ground, so the analysis uses rotation cycles to measure the effect of rotation and tillage on the soil.

The conventional tillage (CT) treatment in this study used a fall chisel plow followed by 2x spring field cultivator tillage treatments. Both CT and no-tillage (NT) treatments were then planted with a no-till planter that used a 13-wave coulter, followed by trash whippers, and double disk openers. For a description of the rotation sequences, see Table 1.

Table 1. Crop Sequence for 2-Crop Rotation Experiment at Arlington, WI (C= Corn, S= Soybean)

Rotated corn has a 13-17% yield advantage over continuous corn (Figure 2). Second-year corn yields 5-7% greater than continuous corn. Third- fourth- and fifth-year corn yields the same yield as continuous corn. Modern corn hybrids and management practices have the same rotation response as older hybrids and practices.

Figure 2. Corn yield response to rotation at Arlington, WI. CC= continuous corn, CS= corn-soybean rotation, xC= number of consecutive years of corn following five years of soybean.

Conventional tillage increases corn grain yield 3-6% compared to no tillage (Figure 3). However, there is an interaction.

Figure 3. Corn yield response to tillage in a corn-soybean rotation at Arlington, WI.

Tillage does not affect corn yield the first year following soybean (CS or 1C in Figure 4). In the second and third consecutive year of corn, tillage interacted with rotation less consistently improving yield 3-6% in the second year, and 8-10% in the third year.

Figure 4. The interaction between rotation and tillage in a corn-soybean rotation at Arlington, WI. CC= continuous corn, CS= corn-soybean rotation, xC= number of consecutive years of corn following five years of soybean.

In conclusion, if rotation is used, then there is no need to do tillage in the first year of the rotation. As the number of consecutive years of corn increase, tillage may be necessary to maintain corn yield.

Record When a Field Tassels to Predict Corn Silage Harvest Date

The 2013 growing season was one of the most extended planting seasons since record-keeping began in 1979. Numerous rainfall events delayed spring field work resulting in planting dates that often range from April to June on the same farm. The range in planting dates will have implications at harvest time, especially for silage.

A good thing to do right now is markdown when corn fields tassel, or more ideally when they silk. Usually silking occurs a couple of days after tasseling, but there have been recent situations were silking is either slightly premature or significantly delayed relative to tasseling. But by knowing your tassel (silk) date, you can begin to predict when a field will be ready for silage harvest.

Use the following in-season guidelines for predicting corn silage harvest date:

1. Note hybrid maturity and planting date of fields intended for silage.
2. Note tasseling (silking) date. 
• Kernels will be at 50% kernel milk (R5.5) about 42 to 47 days after silking.
3. After milkline moves, use kernel milk triggers to time corn silage harvest. 
• Use a drydown rate of 0.5% per day to predict date when field will be ready for the storage structure.
• See http://www.uwex.edu/ces/ag/silagedrydown/  
4. Do a final check prior to chopping.