Corn Silage Harvest: An Exercise in Patience

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I want to start with two statements, or more accurately titles of past articles, that have stuck in my head over the years and serve as a good reminder, as we intently monitor this year’s corn crop and weather conditions.

We will chop no corn before it is ready. ~Ev Thomas
Corn silage harvest is imminent. ~Ron Kuck

Both basically make the argument that harvest will happen. It does every year, and there is no reason to rush it.

A counter to that argument may be that there is a temptation to rush due to fears of a rainy stretch causing muddy field conditions, an unexpected frost or other challenges associated with waiting, and those concerns carry weight for many operations. It’s not fun to harvest in the mud. 

The best we can do is consider those concerns in contrast to the benefits of waiting for the crop to mature.
In terms of making the argument for waiting, the list of reasons is pretty well known:

  • Increase starch
  • Increase dry matter (DM) yield
  • Better fermentation and feed stability
  • Reduced leachate issues

A commonly referenced correlation between whole plant DM and starch content is the gain of approximately one point of starch for each one unit increase in DM.

In 2018 at our Vermont location of the Corn Silage Hybrid Evaluation Program, the same four hybrids were planted on the same date and then harvested one week apart (each hybrid was replicated three times at each harvest date in this data). The results are in Figure 1 below.

image 49

Given the benefits in waiting, a productive conversation can revolve around what can be done to address the risk related to weather and other factors while holding off on harvest as long as needed.

This includes another list of common topics that take on a new level of importance as the month of September winds down.

  • Consider soil drainage and identify fields at the highest risk for mud.
    • Match these considerations with the stage of the crop (see comments on assessing harvest timing below).
  • Determine minimum tonnage needed for feeding lactating animals and try to match that to acres that are the least risky to wait on.
  • Prepare separate storage areas to keep these feeds separate for better utilization at feedout. 
  • Work to open up fields now to streamline the remaining harvest once the corn is at the proper stage for harvest.
    • Store this feed in a separate area.

Executing these strategies may require jumping around to different areas of the farm, and yes, that can add a bit of inefficiency to harvest. But it will all seem worth it when you begin to feedout this year’s crop.

Assessing Fields: Timing from Silking to Silage Harvest

The concept of using growing degree days (GDD), either from planting or from silking, to track the progress of a corn crop and predict silage harvest timing has long been promoted over the use of calendar days and was referenced in fall corn silage harvest resources. The old rule of thumb was 45 calendar days, and this served as a rough estimate in a “normal” year and generally assumed the crop was silking in July when GDD accumulation was abundant. It can take two weeks in late September to receive the same number of GDD as one week in July.

Assessing Plant Maturity and Dry Matter

Another rule of thumb the industry has been trying to move away from  is the use of kernel milkline as an indicator of silage harvest. This is another highly variable indicator and is considered far less reliable than measuring whole plant dry matter (DM).

Personal observations and reports from others regarding whole plant DM measurements show that in many fields, kernels can dry down faster than the rest of the plant. Read more in a South Central New York Dairy & Field Crops Team article , “Setting up Corn Silage Harvest.” Therefore, the crop could be much wetter than the kernel milkline would suggest, making testing of whole plant DM even more critical.

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Joe Laurence, Cornell PRO-DAIRY Forage Systems Specialist 

To read more articles like this one:


Dairy Herd Management

Control Silage Harvest Controllables

Silage Harvest Starts with Planning

Winning the End Game with Corn Silage



Corn Silage: Predicting Harvest and Moisture Level for Better Quality

Whole Plant Moisture – Knowing When to Pull the Trigger on Harvest

Harvest Strategies to Optimize Corn Silage Strategies 


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