Creeping Towards Harvest

Haley Zynda, Extension Educator, Agriculture and Natural Resources, Wayne County, Ohio State University Extension

Silage harvest - it’s the most wonderful time of the year! And by that, I mean stressful and tiring. However, if you were to ask if corn planting or harvesting is more enjoyable, the answer of, “Well there’s no such thing as ‘re-harvesting’ is there?” would sum up my answer quite succinctly.

Since there is only one shot to get it right, you have to make corn silage harvest count. The feed you make in a few days’ time will likely influence your milk yields for the next year. We need to not only be considering maximizing yield, but also maximizing quality. Corn moisture or dry matter, depending on which way you think about it, heavily influences silage yield and the quality of the fermentation and preservation once it is stored. Taking field samples will be essential in getting harvest timing right. You can start to sample for moisture when kernels begin to show denting (just before the appearance of the milkline), or 40 days after silking (for Ohio). Dry matter yield in tons/acre is maximized at a moisture content of 63% (37% DM) according to the University of Wisconsin. Furthermore, silage storage type will also determine how wet the crop should be prior to harvesting (Table 1). I think it’s safe to say that corn chopping will be occurring over the course of a couple days, so keep in mind that corn will lose 0.5-1.0% moisture per day. Therefore, do not start harvesting when the corn is of optimum moisture because the resulting average moisture will be drier than anticipated.

Table 1. Silage storage type and recommended moisture content for corn silage harvest.

Storage Type Moisture, %
Upright silo 60-65
Upright oxygen-eliminating silo 50-60
Bunker 65-68
Bag 62-68

Chop height is another factor to consider when harvesting. Average height of chop is between 7 and 18 inches and can alter the digestibility and yield of silage. According to Pennsylvania State University, raising the cutter bar from 7” to 19” will decrease neutral detergent fiber (NDF) content by about 8% and increase starch content by about 2 percentage points. However, the increase in cutter height decreased yield by about 7%. The trade-off of quality and yield paid off – you can see in Figure 1 the estimated milk yield per ton and acre of silage. Two other research studies also concluded that raising the cutter bar height from 14 to 20 inches or 5 to 18 inches increased daily milk yield by an average of 3 lb/day.

Chop length will also influence quality of silage. The theoretical length of cut (TLC) ranges from ½ to ¾ inch. Shorter cut silage will pack better but will not be as effective of a fiber source if it were longer. If you use a kernel processor, TLC is around the ¾ inch recommendation because the plant is being crushed and compaction in the bunk will be greater. Using a kernel processor will then not only increase digestibility and fermentation capacity of the silage, but indirectly increases the amount of physically effective fiber through increased TLC.

Figure 1. Corn silage cutting height trade-off.

Speaking of kernel processing, how can you tell if it’s working? First, take a dime and try to feed it through the rollers. If it won’t pass through, great! If it does, reset your roller clearance to a height of 0.08 to 0.12 inches. You can see how it affects the silage by taking a silage sample that fits in a 32 oz. cup (a freebie you may have gotten from a co-op or vendor show) and count the number of whole kernels you find in it. There should be no more than 2 to 3 whole or half kernels from silage that has been run through a kernel processor. By crushing the kernels, the starch is more readily accessed by rumen microbes during feeding, thus increasing the rumen starch digestibility.

Before heading to the field, there are a couple of other items to check on.  First, make sure bunkers and silos are in proper condition. Clean out the old feed and scrape the edgesto remove any lingering or caked silage. You can also sweep out the dust using a push broom or broom attachment for a skid steer.  If you use a bunker or bag silo, check the plastic for holes. Patch any plastic that has been perforated with silage tape to prevent spoilage. Think about covering the sides of the bunker to prevent rain spoilage. Ensure the leachate drainage system isn't clogged and there is adequate storage volume.  Approximately 3 square yards of leachate will be produced for every 100 tons of silage stored with 70% moisture, not including any storm water that may interact with the silage (Michigan State University).

Secondly, making sure your chopper is in top working order is an essential part of the equation. Check your knives and shear bar to make sure they don’t need replaced. While you’re taking care of the business end of the chopper, don’t forget to pay attention to bearings and belts that may need to be replaced. Taking care of 20-minute jobs as they come up is preferrable to leaving them until they evolve into a 3-day ordeal.

Don’t forget, not only is harvest stressful and tiring, but it is also rewarding. Keep a log to track all the different aspects of silage harvest that you need to juggle. Knowing the knowledge and tools to make high quality feed not only sets YOU up for success, but also for your cows.  Happy harvest!