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JenREES 10-25-20

Black nightshade in wind-damaged corn fields.
Berries turn from green to black when they ripen.

Grazing Corn Residue: Have received some questions on corn residue management. Cattle grazing can be a beneficial way of residue management if one has access to cattle. Note: I’ve been seeing quite a bit of black nightshade and some horsenettle, particularly in corn fields that had wind damage. Both species have poisonous leaves (increase concentration as plants age) and berries (decrease concentration as berries ripen). Frost doesn’t change toxin levels. UNL forage specialists say when cattle graze corn fields containing nightshade species, there’s enough dilution with the grain, leaf, and husk that poisoning shouldn’t be an issue. We’d recommend watching the cattle as some may prefer grazing the nightshade. I’ve also seen cattle prefer weeds after herbicide applications, so also watch that if fall herbicides are applied. Ultimately, would just recommend don’t turn cattle empty into stalks with significant amounts of nightshade, watch cattle, and don’t graze past the point of 50% of leaf/husk removal. Dr. Jerry Volesky shares more here: https://twitter.com/jenreesources/status/1320513145941692418?s=20.

So, how does one calculate 50% leaf/husk removal and the grazing days for cattle on corn residue? The following is information from my beef Extension colleague, Brad Schick.

  • “There are 8 lbs of grazable dry matter per bushel of corn.
  • Leaf and husk make up 39.6% of the dry matter in corn residue.
  • Intake on corn residue fields will be close to 2% of bodyweight.

Having corn stalks to graze is a great resource for livestock producers. For dry cows, it is a relatively inexpensive feed that can typically meet or come very close to meeting nutritional needs. Grazing can also help get rid of corn remaining in the field and potentially reduce volunteer corn the following year. But are cattle really grazing stalks?

Yes and no. In everyday conversation, grazing corn stalks is said, but the stalk is the last thing cattle eat. Cattle do eat stalks, particularly if they are left on a field too long, but they are primarily consuming leaf, husk, and leftover corn. The stem or stalk makes up about 48.5% of the residue, while the leaf blade and husk make up 39.6%. Cattle will consume leaf and husk if available. That diet will consist of 52 to 55% TDN (total digestible nutrients) and 5 to 5.5% crude protein.

When thinking about how long to graze corn residue, the calculation to follow is that for every bushel of corn produced, there is 16 lbs of dry leaf and husk. The recommended grazing plan should be to remove 50% of the leaf and husk. This assumes that portions of the forage will also be lost to trampling, defecation, and other considerations such as wind. That leaves 8 lbs (16 lbs X 50%) of good forage on a dry matter basis that is available for consumption for every bushel of corn.

For example, say the field produced 200 bu/ac corn. By the calculations, there is 1600 lbs of dry matter per acre available (8 lbs X 200 bu = 1600 lbs). A 1000 lb animal will consume about 26 lbs of dried forage per day which means a 1300 lb animal will consume about 34 lbs per day. However, with lower quality forage such as corn residue, intake will be closer to 2% of bodyweight. In this example, that means closer to 26 lbs for the 1300 lb animal. So, how many days of grazing is that? By the calculations, there are 61 days of grazing for one cow grazing one acre (1600 lbs DM ÷ 26 lbs = 61 days). A general rule is about 30 cow days per 100 bushels/acre of corn produced.

Calves and replacement heifers can be also be a great option but will need a protein source in order to meet their growing requirements. Not only is grazing corn residue good for the cattle producer, but it is also good for the crop producer. Studies from the University of Nebraska-Lincoln have shown that grazing corn residue increases or at least maintains crop yields. (Grazing Corn Residue: A Win-Win for Crop and Cattle Producers).” More info. can be found at: https://go.unl.edu/fsa9.

JenREES 12-2-18

Part 2 of my residue management series focuses on grazing corn residue. We’re blessed cattle in corn stalksin Nebraska to have corn, cattle, and ethanol with the distiller’s co-product…the golden triangle as it’s been dubbed. What’s interesting is that a huge feed resource in corn residue is under-utilized each year, with an estimated 52% of our state-wide corn residue being grazed or mechanically harvested.

Because a small amount of residue is removed, many fields in Nebraska have potential for grazing, except for the case of extreme slope and/or very low yields. Regarding stocking rates, Dr. Mary Drewnoski, Extension Beef Nutritionist shares, “Corn residue is about 10% husk and 34% leaf with the remaining residue being stalk and cob. Recommended stocking rates are based on the ability of a pregnant cow to maintain body weight without supplementation of protein or energy. The rates suggest that you can graze a 1200 lb cow for 30 days for every 100 bu. of corn grain produced. This would result in the cow consuming only about 12% to 15% of the corn residue in the field and nearly all would be husk with some leaf. Cob and stalk have less energy available.”

Compaction is the main concern I hear for not grazing. An increase in a soil’s bulk density and penetration resistance can be indicators of compaction. A summary of Nebraska research studies when corn residue was grazed at proper stocking rates has shown fall and winter grazing:

  • do not significantly impact soil properties that would lead to compaction;
  • don’t result in changes to soil organic matter, N, P, or K (just uneven distribution of the nutrients excreted back onto the land);
  • results in maintained or increased yields; and
  • increases soil microbial activity.

Grazing corn residue resulted in no detrimental effects on soil properties (sixteen years in silty clay loam soils) including bulk density and penetration resistance. Increase of surface roughness was observed where cattle congregated for water and during wet conditions when soil was thawed. An Iowa study indicated the surface roughness could impact seed placement for the following no-till crop but only found that in one location in one field studied. In another study of five Eastern Nebraska locations, penetration resistance was slightly increased in two of the locations but was below the threshold for impeding root growth and did not carry over into the next year. There were no yield differences between grazed and ungrazed treatments whether continuous corn (239 bu/ac for grazed and 223 bu/ac for ungrazed) or soybean (grazed 59 bu/ac and ungrazed 62 bu/ac) in the three years at those five locations. Sixteen years of fall grazed corn residue (November to February) resulted in a statistical soybean yield increase of 3.4 bu/ac in Eastern Nebraska. There was also an increase in the soil microbial community in the grazed treatments vs. ungrazed for those sixteen years. Under continuous corn in western Nebraska, five years of fall grazing corn residue did not statistically impact yields (154 bu/ac grazed vs. 148 bu/ac ungrazed).

Some have mentioned that the weather is not allowing them to till this fall. Perhaps cattle grazing is an option? Regarding the questions I’m receiving about this: The tenant in cash rent situation owns the stalks unless the landlord has specified otherwise in the written lease. Specify in the grazing lease who takes care of fence, water, and monitoring cattle. To help connect cattle and crop producers for utilizing residue and forage cover crops for grazing, there’s a free resource called The Crop Residue Exchange at https://cropresidueexchange.unl.edu/. After establishing a log-in account, growers can list cropland available for grazing by drawing out the plot of land available using an interactive map. They can then enter basic information about the type of residue, fencing situation, water availability, and dates available and provide their preferred contact information. Livestock producers can log in and search the database for cropland available for grazing within radius of a given location of interest. There’s also an ‘Other’ category where growers can list forage cover crops for grazing. Grazing rates are listed as either a ‘per acre’ basis or ‘rate/head/day’. An excel spreadsheet called the ‘Cornstalk Grazing Cow-Q-Later’ may be of help to determine rates at this site: https://go.unl.edu/2fb6. There’s more I’d like to share but for additional resources, please see my blog site at: http://jenreesources.com or contact your local Extension Office.

Of importance is to double check in-season and fall-applied herbicide labels for any grazing restrictions. These restrictions can also be found in the ‘Forage Feed Grazing Restrictions’ in the UNL Guide for Weed Management. The forage, feed, and grazing restriction only applies to the crop for which the herbicide was applied. When it comes to grazing cover crops planted into these residues, one must use the replant/rotation restriction guidelines found on the herbicide label and in the UNL Weed Guide: ‘Replant Options Rotation Restrictions’.  If the label doesn’t specify any restrictions, then it should be ok. If you want to be on the safe side, a rule of thumb is to use the pre-harvest interval for the amount of time to wait before grazing stalks.


Resources:

UNL Grazing Corn Residue Research

Many stalks in Nebraska are left ungrazed for various reasons.  One reason I’ve heard is the potential impact of increased compaction and reduced yield of the next crop.  Nebraska Extension has long-term research addressing this concern…in fact, 16 years of research conducted at the Ag Research and Development Center near Mead.  There’s various components to this study and you can view the full report at: http://go.unl.edu/8mp6.

In this study, cattle were allowed to graze corn residue in the spring (February to mid-April) or the fall (November through January) and these treatments were compared to an area not grazed.  Corn and soybeans were planted the spring after grazing the residue for 16 years to determine the effect of grazing on the subsequent crop yield.

In the fall grazing treatments, the corn and soybeans were planted no-till.  For corn or soybeans planted into the spring grazing treatments, three tillage treatments were also implemented for nine years:  no-till, ridge-till, and spring conventional till, after which all treatments were converted to no-till.  This result of the tillage by spring grazing treatments for either corn or soybean yield over nine years showed no interaction and suggested the same effect on yield regardless of tillage treatment used after spring grazing.

Table1-Beef

Effect of Corn Residue Removal on Subsequent Crop Yields“, 2015 Nebraska Beef Cattle Report. Mary E. Drewnoski, L. Aaron Stalker, Jim C. MacDonald, Galen E. Erickson, Kathy J. Hanford, Terry J. Klopfenstein

Spring grazing across all tillage treatments did increase soybean yields statistically (58.5 bu/ac for spring grazed vs. 57.0 bu/ac for ungrazed) and had no effect on corn yields.  The results were similar looking at 16 years of grazing vs. not grazing under no-till for both corn and soybeans in the spring; there was no yield effect found for corn and the soybeans showed a slight yield increase with grazing.

Table2-Beef

Effect of Corn Residue Removal on Subsequent Crop Yields“, 2015 Nebraska Beef Cattle Report. Mary E. Drewnoski, L. Aaron Stalker, Jim C. MacDonald, Galen E. Erickson, Kathy J. Hanford, Terry J. Klopfenstein

Looking at a 10 year period of no-till management for both spring and fall grazed corn residue and subsequent corn and soybean crops, fall grazing statistically improved soybean yields over both spring grazing and no grazing (65.5 bu/ac vs. 63.5 bu/ac and 62.1 bu/ac respectively).  No grazing effects were observed on corn yields in either season.  All statistics were at the 95% confidence level meaning the researchers were 95% confident any yield differences were due to the treatments themselves vs. random chance.

Regarding compaction, in the fall, the field was typically frozen and the researchers felt any mud and compaction associated with grazing cattle was minimized; highest subsequent soybean yields were achieved with fall grazing.  The spring treatment was designed to look more at potential compaction and muddy conditions after spring thaw till right before planting-thus the implementation of different tillage treatments as well.  They used a stocking rate consistent with UNL grazing recommendations resulting in removal of half the husks and leaves produced (8 lbs of leaf and husk per bushel of corn grain produced).  Results of this study indicate that even with muddy conditions in the spring, grazing increased subsequent soybean yields compared to not grazing regardless of tillage system used and that corn yields were not different between grazing vs. not grazing and regardless of tillage system used in the spring.  This study was conducted in Eastern Nebraska in a rainfed environment with yields ranging from 186-253 bu/ac with a 16 year median yield of 203 bu/ac.

Additional Grazing Study

A five year fall grazing study (December through January) was conducted in an irrigated continuous no-till corn field at Brule, NE to determine the effect of corn residue removal via baling corn residue or fall grazing on subsequent corn yields.  That environment receives limited rainfall and residue is deemed important for reducing evaporation of soil moisture in addition for catching/keeping snow on fields.  Farmers were questioning the effects of any residue removal on subsequent corn yields and the study was implemented.

Treatments were 1) fall grazing at 1 animal unit month/acre (AUM), 2) fall grazing 2 AUM/ac, 3) baled, or 4) ungrazed.  The researchers found that residue removal did not affect corn grain yields from 2009-2013 in the continuous corn rotation.  There were no statistical yield differences with 5 year average yields of:  152 bu/ac, 155 bu/ac, 147 bu/ac and 148 bu/ac respectively for the above-mentioned treatments.

Table3-Beef

Effect of Corn Residue Removal on Subsequent Crop Yields“, 2015 Nebraska Beef Cattle Report. Mary E. Drewnoski, L. Aaron Stalker, Jim C. MacDonald, Galen E. Erickson, Kathy J. Hanford, Terry J. Klopfenstein

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