The basics of an optimum corn silage harvest require a lot of time and experience. This time is justified, as these steps are critical to a successful harvest where the decisions made during a very short time period impact the farm’s production performance and economics for the upcoming year.
These important decisions include harvesting at the proper dry matter, adequate kernel processing, proper length of cut, and proper packing and covering of bunk silos. An overview of this information is covered in Setting the Stage for Success: Corn Silage Harvest. The following will cover additional considerations for understanding and managing forage quality.
As part of the Corn Silage Hybrid Evaluation program, we have focused significant attention over the last two growing seasons on the interactions between growing environment and corn silage forage quality. While this work is still developing, it does build on earlier knowledge of the impact of growing conditions on plant development and provides some insight into managing the corn silage crop for forage quality.
Plant Development, Weather and Fiber Digestibility
Plant physiologists have long understood that characteristics of corn ear development are determined early in the growing season. Before the crop even reaches the reproductive stage of growth, it has already determined the number of kernel rows per ear and the number of kernels per row. It is also understood that hot weather around the time of silking (three to five weeks) can lead to increased lignin content in the plant.
In recent years, long-term fiber digestibility measurements by laboratories have become more common. Neutral Detergent Fiber (NDF) digestibility at 30, 120 and 240 hours is now commonly measured, as well as the undigested NDF (uNDF) at these same time points. In 2015 and 2016, the Dairy One Forage Lab conducted a study where they tracked season-long weather information and measured its impact of uNDF content on the silage.
Some notable results include:
- Decreases in fiber digestibility (increases in uNDF) as both precipitation and heat accumulation increased throughout a growing season, with the most significant impacts in lowering fiber digestibility found during the months of:
- August for rainfall (particularly at 240 hours)
- June for Growing Degree Day (GDD) accumulation (particularly at 30 hours)
Corn Silage Chopping Height Considerations
Corn silage harvest height tends to be a topic of discussion in years of above-average yields or significant carryover from the previous year. As we enter the 2018 harvest season, many farms have adequate carryover of (generally lower digestibility) corn silage. 2018 crop conditions vary greatly, and while some areas may be faced with below-average corn silage yields, there are areas of the state where yields are expected to be above average. For some, the prospect of having a corn crop with better fiber digestibility to dilute out the remaining inventory of poorer 2017 corn silage is of interest.
A number of studies have been conducted to determine the pros and cons of varying the cutting height of corn silage. Given the significant impact that growing season and other management factors can have on forage quality, it is not surprising to see some variation in the end results. This is also true of the magnitude of impact that cutting height can have on corn silage. However, when averaged together, we can develop a few “rules of thumb.” In general, when starting with a cutting height of 6 to 8", raising the height of cut by approximately 12", to 18 to 20 total inches, will result in the loss of approximately 2 tons per acre of yield (at 35% dry matter), but will gain five to six percentage points of NDF digestibility.
To learn more about chopping height and taking forage samples to map forage quality, click here.
Original article written by Joe Lawrence, Cornell CALS PRO-Dairy, and Margaret Quaassdorff, NWNY Cornell Cooperative Extension.
Headline image courtesy of the William H. Miner Agricultural Institute.
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