Corn silage refresher – Part 1: How to set your cutting date

Martin J. Mangual, Michigan State University Extension - September 15, 2017

Establishing the time for harvest is vital to maximize the value of the corn silage, but how do you know when to cut?

The time for chopping is here, therefore it is important to remember what factors can help you to maximize the value of your corn silage. This article will cover general points that will allow you to optimize this year’s harvest by discussing the general rules that should guide your decision of when to cut.

There is only one shot at harvesting the optimal corn silage for your cows, and deciding when to cut could determine the packing capacity, the potential of optimal fermentation and, more importantly, the digestibility and value of the nutritional profile. There are many factors that can be used to guide the decision of when to cut.

Many farmers opt to follow different guidelines such as days after tasselling, denting of the kernels or the kernel milk line. These could be used as guides to track plant maturity but should not be the main determinant to make a decision to chop. Maturity signs can help you determine when is a good time to start collecting samples to determine whole plant dry matter (or moisture content).

Dry matter (DM) or moisture content should be the main determinant that drives your decision of when to cut. The general recommendation by Michigan State University Extension is to aim for a window between 32 to 35 percent DM (68 to 65 percent moisture). However, other university research recommends that the optimal value could change depending on the structure being used to store the silage.

The recommendation for bunks and drive-over-piles is to harvest between 30 to 35 percent DM (70 to 65 percent moisture) thus, aiming for 33 percent. The amount of moisture is extremely important to obtain a dense packing of the corn silage which excludes air to allow proper fermentation. If your harvest will be stored in bags or upright silos, MSU Extension recommends that corn silage is harvested between 35 to 39 percent DM (65 to 60 percent moisture). Bags and uprights allow for additional dry matter to be harvested because the techniques used for packing are different thus allowing harvest to be executed with a lower moisture content. Silage harvested at higher-than-prescribed moisture levels can produce substantially more leachate resulting in other negative consequences.

DM can be tested on-site using a food dehydrator, a Koster moisture tester or even a conventional kitchen microwave oven. If the ideal DM or moisture content is close to your target, you can estimate cutting time following this general rule: corn will increase between 0.5-1 percent DM per day so this allows the use of DM to estimate when the corn is ready to be harvested. For example, if a sample tests for 30 percent DM and will be stored in a pile it could be harvested within a week. Remember that cutting at the proper DM is one of the key components to maximize nutritional value, ensure proper fermentation and ultimately, have the best results when fed in future rations.

This article is one in a series of three that covers corn silage harvest from the decision of when to cut and when to feed the silage.