Ensiling Immature and Frost Damaged Corn
Peter Jeranyama, Extension forage crops specialist, Plant Science Department
Cody Wright, Extension beef specialist, Department of Animal and Range Sciences
Kent Tjardes, Extension beef feedlot specialist, Department of Animal and Range Sciences
Immature corn is corn that fails to reach adequate maturity and can not be sold at normal, prevailing market values
without steep price discounts. Corn that is drought stressed, heat unit deficient, water logged, or frost damaged
meets this definition.
Corn is uniquely suited to silage making. But when corn is damaged or killed by frost before it reaches the desired
maturity for ensiling, the stage of maturity at the time of frost is very critical. If frost is early and green leaves remain
on plants it may be best to let the crop stand, as it will continue to accumulate dry matter, until the whole plant moisture
content nears 63 to 68%. Partially frosted corn appears deceptively drier than unfrosted corn at the same moisture content.
If plants are killed by frost at an immature stage they will contain higher moisture content than is recommended for
ensiling. They will dry down very slowly. However, if frost sets in close to silage harvest time, harvest the crop immediately.
If the crop becomes too dry, consider a finer chop and adding water or wet forage during ensiling.
The optimum corn silage harvest stage for maximum energy yields is between 63 to 68% moisture content and
at the 2/3-milk line maturity stage. The milk line can be viewed on the tip of a representative ear that has been broken
in half.
However, the relationship between milk kernel line and whole plant moisture content is highly variable. Milk line
should only be used as an indicator of when to start monitoring whole plant moisture content. The trigger for corn
silage harvesting is the whole plant moisture content.
If corn is harvested at more than 70% whole plant moisture content,
the result will be:• lower dry matter yield per acre.
• increased seepage losses (nutrient loss).
• reduced dry matter intake, as silage has a sour taste and odor.
• lower milk production or reduced weight gains when fed.
If corn has less than 60% whole plant moisture,
• no dry matter yield benefit; yield most likely will be reduced 5-10% due to leaf loss.
• potential silage mold problems and mycotoxin levels increase as fermentation is hampered.
• dangerous levels of heat production.
• potential reduction in nutritive value due to heat damage, reduced starch digestion, and reduced fiber digestion.
• reduced milk production or weight gains.
Corn dries at an average rate of 0.5% of whole plant moisture content per day. Environmental conditions such
as cool, wet weather can slow down rate of drying, while hot and dry days tend to accelerate drying rate. However,
0.5 % per day is a good rule-of-thumb for predicting when fields will be ready for chopping for the type of
storage you plan to use.
| Table 1. Recommended moisture contents for corn silage stored in various silos. | |
|
Type of Silo |
Recommended moisture content for ensiling, % |
|
Horizontal Bunker Bag Upright concrete stave Upright oxygen limiting |
65 to 70 60 to 70 60 to 65 50 to 60 |
Source: NCR574 (1995)
Cut two to four representative corn plants from the field at silage cutting height, chop them into small pieces (e.g.,
with a brush chipper), and mix well in a 5-gallon bucket. On a paper plate weigh out exactly 100 grams of fresh
silage, and adjust for the weight of the paper plate. Spread the silage evenly on the plate, place in microwave, and
heat on high for 4 minutes. Remove, weigh, and record. Repeat procedure on high for 1 minute, and weigh and
record. Repeat procedure until the weight of the sample remains constant. At this point, the weight is the dry matter
(DM) of the silage. Calculate the moisture percentage by subtracting the dry matter weight from 100.
Stressed conditions
Under stressed conditions such as during a frost or drought, corn tends to accumulate higher levels of nitrate
than normal. Producers generally have the option of cutting corn at various heights ranging from 6 to 18 inches.
Determine cutting height by prioritizing your need for maximum crop yield or for high quality silage.
Cutting at 18” is associated with
• lower dry matter yield per acre.
• low concentrations of NDF, ADF, and lignin associated with better forage quality.
• increased estimated milk yield per ton of fed silage.
• a similar estimated milk yield per acre compared with a 6-inch cut.
• less soil erosion.
• lower silage nitrate levels.
Strategies to reduce corn silage moisture content
As a rule of thumb, 30 lb DM/ton of silage of the following materials, when they are at 100% dry matter content,
will reduce moisture content by 1%:
• ground grain.
• chopped straw, but it may decrease fiber digestibility/energy.
• chopped hay, which may increase forage value.
When adding dry matter to silage, it is critical to mix it well and make sure the stack is well packed to ensure
proper fermentation.
References
NCR574. 1995. Corn silage production, management and feeding.
ASA-CSSA-SSSA, Madison, WI.