How long can crop residue be grazed?

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Corn snow
A harvested corn field, with snow.

Corn and soybean harvest is wrapping up around the State of Ohio, and for most producers, this is earlier than normal. As a young producer, I cannot recall an autumn season quite like the one we experienced in 2022. 

The mild temperatures paired with dry weather conditions allowed producers to get their crops harvested in a timely manner without causing damage to the fields such as compaction and rutting. 

Yields were nothing to sneeze at this year as well. Adequate precipitation and plenty of heat during the growing season allow for above-average yields for both corn and soybeans. In my neck of the woods — southern Ohio — disease and insect pressure were also low, making for healthy crops well into the later half of the growing season. 

As a result, many producers are looking at freshly harvested fields loaded with residue — some might be tempted to fire up the tractor and hitch up the plow to incorporate the residue; some might be tempted to pull out the baler and roll up the residue, and then some might just mow or chop up the stalks. These are all very common practices and serve their purposes in certain situations, but they all have a common theme — they all cost you money. 

With record high fuel prices and part shortages, and if you are like me, labor and time-restricted, you might want to consider letting the livestock take care of the job. 

Grazing crop residues can be a great way to extend the grazing season in turn reducing the amount of stored forages needed to during the winter season. 

Drawbacks

Unfortunately, crop residues are not known to be the most powerful feed in the feeder; they contain higher fiber, low protein and lower levels of digestibility. Another drawback is infrastructure; in Adams County, it’s not uncommon to find a spring water tank in the middle of a corn field that is also completely fenced, but in the majority of the state, this is not the case. 

Location can also be a drawback to grazing crop residue because not every crop field Is next to your existing pasture, and loading up livestock and hauling them 10 miles down the road is not the exciting activity in the world. 

Quality

With all of that said, let’s say you have a great opportunity to harvest some crop residues through livestock. You might be pondering how long does the residue stay suitable for livestock to consume? From the day of harvesting the crops, the time begins to tick on quality and quantity. 

So first let’s address the quality issue. Different crop residues will vary in quality, but for Ohio, we tend to be dealing with two main types of residues, corn stalks and soybean stubble. 

Corn residue can be broken down into multiple components, the stalk, cob, grain and leaves. The highest quality will be in the grain and leaves, the lowest quality components will be the cob and stalk. On average, putting all the plant residue parts together 6% crude protein and 40-45% dry matter digestibility can be expected. 

Soybean stubble can be very similar in quality, with a crude protein level ranging from 4-6% and dry matter digestibility ranging from 35-40%. 

Quantity

Quantity is the factor everyone is looking at when it comes to grazing long and feeding less hay. The estimated amount of reside available for grazing is based on crop yield. 

The University of Nebraska has some great data that breaks down the amount of residue per bushel of grain yield, but in summary you can estimate 13-16 pounds of residue per bushel of yield. You can see the full details at beef.unl.edu/keys-corn-stalk-grazing. 

My average farm corn yield for 2022 was estimated at 160 bushels/acre; in essence, this means I would roughly have 2000-2500 dry matter pounds/ acre to graze. There are many factors that can influence the ratio of leaves, husk, cob and grain amounts such as hybrid varieties, combine adjustments and crop standability. 

Now that we know the quality and quantity of feed we have in the field ready for harvest, it’s time to address the original question to this article:  how long can one graze the crop residues? 

How long?

There are multiple factors that account for how long crop residues can be utilized as a feed source including the following: 

  • Weather: This factor will have a great effect on how long a producer can graze crop residues. As winter weather sets in, rain, snow, freezing and thawing of the soil can decrease quality and degradation of the residue; remember we are competing with soil biology for food.
  • Residue types: Different crop residues will break down differently due to their carbon-to-nitrogen ratio, which is the ratio of mass of carbon to the mass of nitrogen within the plant structure. Crops with high amounts of lignin will break down much slower due to having high amounts of carbon. For example, corn residues is thought to have a C:N ratio of 57:1 compared to soybeans stubble of 25-30 C:N ratio. This means soybean stubble will be broken down much faster by soil microbes and weathering. 
  • Livestock Species: Different types of livestock have different amounts of intake; size and age of the animal will also play a role in intake. For all my beef producer friends striding for large, framed females, a 1400-pound brood cow will consume anywhere from 2.5-3% of her body weight, but due to the high amounts of fiber and time spent sorting through the crop residue (looking for the candy corn), it is thought that on average you can expect an intake of 1.8% of body weight. This equates to about 25 pounds per head.
  •  Stocking rate: We know our cows will consume about 25 pounds of dry matter residue per day and we have about 2500 pounds of dry matter per acre available. But remember, roughly 50% of this residue will be consumed equating to 1250DM pounds available to the livestock. With this information, we can adjust our stocking rate to get the most out of the residue by managed grazing practices. 

Example: 1 1400 pound cow = 1.4 animal units and will consume roughly about 35DM pounds/day or x 30 = 1,050 pounds a month. With available residue that will actually be consumed, 1250 pounds ÷1,050 pounds consumed per month = 1.19 Animal Units x 30 days in a month = about 38 days of grazing. 

Let’s say you stock feeder calves weighing 500 pounds/head 1400 pound cow ÷ 500 pound calf = 2.8 x 38 days = 106 grazing days available. 

In summary

Crop residues can be a great resource for grazers looking to utilize unused forage matter and reduce stored hay consumption. 

There are many factors to consider before beginning the grazing process, and supplemental nutrition should be considered due to the lower nutritional quality of crop residues. 

Crop residues do not last forever, and many factors can dictate how long the grazing period will last, but one thing is for sure, livestock don’t cost $5.00/gallon and you don’t have to worry about trying to find a part to fix them. Happy grazing! 

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Richard Purdin is the ag and natural resources and community development educator for OSU Extension, Adams County. He can be reached at purdin.19@osu.edu or call 937-544-2339.

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