This year there is a lot of concern about asynchronous drydown of the corn silage crop. Farmers are concerned that the grain will get too hard and be drier than stover when harvested and placed into the storage structure. In this article I would like to examine, some of the principles behind timing the decision to begin silage harvest.

From our experience, I would be surprised if corn grain dried synchronously with corn stover. It does happen in dry years (Figure 1). But in normal and wetter years, corn stover is wetter (especially at the base of the stalk) than corn grain and stover dries at a slower rate (Figure 2). We have observed asynchronous drydown numerous years and in experiments where we adjust cutting height.

Most corn silage choppers have kernel processors. Even though corn grain and stover may have different moistures, when these plant parts are mixed, moisture will migrate from wetter to drier parts. What is important to remember is that the whole-plant moisture must be at the recommended level for the storage structure.

The fact that corn stover and grain plant parts drydown asynchronously offers farmers a management option. If corn silage is too wet, but the field must be chopped, then by raising the cutter bar whole-plant silage moisture will decrease. This could be especially useful when working with custom operators and timing corn silage chopping. The farmer will give up some yield although is is the lowest quality part of the plant.

Figure 1. Moisture change of corn plant parts at Arlington during 2005.

Figure 2. Moisture change of corn plant parts at Arlington during 2006.

The following in-season guidelines can be used to predict corn silage harvest date:

Note hybrid maturity and planting date of fields intended for silage.

Note silking date. Half milk of the kernels will typically occur about 42 to 47 days after silking.

Once kernel milkline begins to move, measure moisture of fields intended to be harvested for silage. Use 0.5% per day to predict date when field will be ready for the storage structure.

Final check prior to chopping.

In most years corn stover is wetter than corn grain at the time of corn silage harvest. Drydown of these plant parts is usually asynchronous, except in dry years when the drydown rate is similar between stover and grain. If a custom chopper arrives on the farm and is pushing to begin chopping and the farmer does not need all of the forage he is producing, then the cutter-bar of the chopper can be raised and silage moisture will decrease 2.0 to 3.7 percentage units of moisture. Remember though that there is a yield v. quality v. moisture trade-off that will occur as cutting height increases.