Corn Silage Chopping Height

Contributed by Joe Lawrence – Cornell PRO-DAIRY

I know some farms/areas have wrapped up CS harvest and some are just starting but I have been getting a number of questions about chop height the last few days. For the most part, these questions are being prompted by abundant hay inventories and expectations of good corn silage yields. Another factor that is playing in is the expectation of lower fiber digestibility with the high rainfall in July and August.

The yield penalty is notable but there are gains to be made in starch and fiber digestibility. To me a bigger issue is storage space.  We know when we over-fill bunk silos, put up temporary piles or even put silo bags in less than ideal locations that storage losses increase rapidly. For this reason, I would much rather harvest less tons of higher quality stuff and make sure it can be properly stored than to harvest more tons of lower quality and put it into situations where losses will be significant.

Much of what we have on Cutting Height references a Penn State article that summarized the known research on the topic:

Considerations in Managing Cutting Height of Corn Silage

Here is an excerpt from an article Margaret Quaassdorff and I put together a few years ago. As well as a slide I have used on the topic.

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 and Penn State provides a good review these. 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 six to eight inches, raising the height of cut by approximately 12 inches, to 18-20 total inches, will result in the loss of approximately two tons per acre of yield (at 35% dry matter), but will gain five to six percentage points of NDF digestibility. Furthermore, given the fact that you will be harvesting less stalk but the same number of kernels, the percentage of starch in the resulting silage will increase.

In addition to the factors already discussed, the apparent interaction between Fiber Digestibility and Soil Type is another piece of relevant information from the Dairy One study and the Corn Silage Hybrid Evaluation program. Preliminary data indicate a trend of lower fiber digestibility on heavier soils. The work by Dairy One found that Hydrologic Class A (well-drained soils) were lower in undigested NDF (uNDF) than other soil classes.