Preparing for corn silage harvest using growth stages as a guide

Corn tassel time and the days until the half-milk line is the target for when to harvest silage.

Mid-July may seem like an unlikely time to prepare for corn silage harvest, but it is an excellent time to consider the timing for harvest based on when the corn plant tassels. Many producers had an extended corn planting season this spring and consequently the range of harvest for silage will vary considerably. Research done at Michigan State University compared short-season and late-season hybrids planted at successive planting dates to determine the affect of planting date on corn growth. In general, late planted corn required fewer growing degree days (GDD) to complete vegetative and grain fill stages than early planted corn.

To assist growers in their plans for silage harvest, they can predict when a field will be ready by knowing the tassel (silk) date. Silk dates (R1) occur when corn plants are at maximum or near maximum height and have maximum vegetative dry matter.

The silking period is the most sensitive period for the crop. Silks on the ear must be present while pollen shed occurs for successful pollination and fertilization. Producers can use the day of silking as the start of the reproduction process and a guide for when to harvest. When the corn plant reaches the half-milk line, approximately 42 to 47 day after silking, plants will normally have 40 percent moisture and 97 percent of their total dry weight.

Joe Lauer, University of Wisconsin forage agronomist, has the following guidelines to use 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 percent kernel milk (R5.5) about 42 to 47 days after silking.
  3. After milk line moves, use kernel milk triggers to time corn silage harvest.
    −         Use a dry down rate of 0.5 percent per day to predict date when field will be ready for the storage structure.
  4. Do a final check prior to chopping.

For more information, contact Phil Kaatz, Michigan State University Extension educator, at or 810-667-0341.

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