What a beautiful week weather-wise! The winds this weekend have allowed leaves to drop from deciduous trees/shrubs. With the temperature fluxes this fall, many trees and shrubs still maintained leaves in spite of hard frosts. They hadn’t completely formed an abscission layer (cells at the attachment point where the leaf petiole meets the stem). Now that leaves are falling, it’s important to keep them mulched into lawns or raked up to avoid conditions like snow mold in lawns. Leaves are also great materials to add to vegetable and flower gardens as they can improve organic matter and act as a mulch. If added to perennial flower beds, make sure to remove the leaf material when hostas begin to leaf out in the spring. This is because slugs decomposing leaf litter also like to feed on plants such as hostas.
Residue Management: My goal in writing about residue management is to share recent research to aid in answering questions received. There’s a lot of ways that corn residue is managed: processing with the combine, various types of tillage, grazing, baling, spraying products, and cover crops (with thought of lowering Carbon:Nitrogen ratio and increase microbial populations). On a year to year basis, depending on the soil moisture and temperature, combinations of these practices may work well for individual field situations. Unintended consequences of practices include wind and water removing loose residue and/or soil from fields.
A few recent questions have included impacts of spraying various products and also about spraying nitrogen. While I know farmers have tried various products, sugar, and applied UAN to corn stalks, we didn’t have any on-farm research studies with those products for the purpose of residue decomposition, so don’t have data to share. Data is also very limited in scientific journals. If any of you considering products would be willing to test them via on-farm research, please let me know and I’d be happy to help you set that up and help with data collection.
There is a recent study from Illinois where residue management included using Calmer Bt chopper stalk rollers that sized residue into smaller pieces vs. standard stalk rollers. In addition to each mechanical control treatment for residue management, AMS or a biocatylist product were also added. The researchers found a 7% enhanced reduction of corn residue with the chopped residue vs. the standard stalk rollers (46% compared to 39% reduction) but there were no differences with the addition of AMS or the biocatylist product.
Iowa State conducted a three year study evaluating the effects of conventional tillage, no-till, and strip-till on residue breakdown on Bt and non-Bt corn residues. They did this by placing bags of residue of Bt and non-Bt hybrids in the three different tillage systems and evaluated decomposition after 3, 6, 9, and 12 months in a corn/soy rotation. The results showed no significant difference between tillage systems or Bt and non-Bt hybrid decomposition (34-49% of residue remained in all treatments).
These researchers also studied the impact of nitrogen applications on corn residue breakdown over two years in no-till. Immediately after harvest, three N rates (UAN 32 percent) of 0, 30 and 60 lb N/acre were applied to corn residue. A specific amount of residue was placed in nylon mesh bags and left in the field for 3, 6, 9, and 12 months, after which residue decomposition was evaluated. The different rates of N resulted in no differences in rate of decomposition. In general, the longer the residue remained in the field, the more it decomposed over time, regardless of N rate. Thus the authors shared that applying N after harvest for residue decomposition was not effective nor economical as soil and air temperatures decreased over time after harvest. They shared that in general, decomposition of crop residue is primarily influenced by soil moisture (near field capacity) and temperature (above 50F) as these factors influence microbial activity.
This year we’ve seen quite an increase in baling of soybean residue in the area. I’ve also heard this in other parts of the State. Soybean residue can be used for bedding, or for feed as roughage or mixed with distiller’s grains. In speaking with farmers and livestock producers, there’s perhaps a number of reasons why we’re seeing an increase in soybean residue acres baled this year. While we’re not short on corn residue, the late harvest delayed baling of corn residue for some and they were looking for another forage source. Hay prices have been higher this fall and continue to increase, making soybean residue a less expensive alternative. Some crop growers may also have been seeking added income.
Some colleagues and I addressed questions we were receiving in a recent UNL CropWatch article. Questions have centered around the value of this residue. I’ve shared in previous articles that approximately 1 ton of corn/grain sorghum residue is produced for every 40 bushels. For soybeans, it takes 30 bushels to produce 1 ton of crop residue. So to give an example, a corn field averaging 240 bu/ac would result in approximately 6 tons of residue/acre. In comparison, a soybean field averaging 60 bu/ac would only produce 2 tons of residue/acre.
In general, there’s not too much difference in the amount of nutrients removed from corn vs. soybean residue.
- Corn (17 lbs N, 4 lb P2O5, 34 lb K2O, 3 lb S)
- Soybean (17 lbs N, 3 lbs P2O5, 13 lbs K2O, 2 lbs S)
To determine the value of these nutrients, one would need to know the current fertilizer nutrient price per pound. Value also includes maintaining soil properties, which is harder to place a value upon. Based on the research, it’s recommended to leave at least 2 tons/acre of residue in the field to maintain soil organic matter. More needs to be retained for many fields to prevent excessive soil erosion and some fields should not be harvested. In previous articles, I shared our best management practices to consider for removal of corn residue. In the corn field example above, 6 tons of residue are available. Removing 2-3 tons of residue still leaves 50% or more residue on this field. In comparison, the soybean field with 2 tons/acre of residue at harvest is already at the 2 ton/acre limit to maintain soil organic matter. Regular soybean residue removal is not recommended as it is expected to result in reduced organic matter and increased soil erosion.
Soybean residue is a lower quality feed than corn, sorghum, and wheat residue. Forage tests show a range of 35-38% total digestible nutrients (TDN) and 3.9-4% crude protein; these numbers are less than wheat residue. For comparison, forage tests from corn residue ranged from 47-54% TDN and 4.5-6.5% crude protein (sorghum residue would be similar). The highest edge of those ranges would be similar to average grass hay.
USDA showed a price of $50/ton for soybean residue. Assuming 88% dry matter (DM), then that is $162 to $189/ton of TDN with 4% crude protein. In comparison, corn residue bales were $60 to 65/ton. Assuming 83% DM and 50% TDN, corn residue is a better deal (on an energy basis) at $150 to $156/ton of TDN with 5-6% crude protein. For perspective, good grass hay is $85 to $100/ton. Assuming 88% DM and 55-60% TDN, it is $160 to $205/ton TDN. A true economic analysis would take into consideration the residue removal costs, nutrient removal, and potential for soil loss (even though it’s hard to put a value on that). The 2018 Nebraska Farm Custom Rates shows rates for cornstalk raking and baling. Soybean residue removal numbers aren’t provided.
As a source of dry matter, soybean stubble is a low cost source for feedlots. However, soybean stubble is less valuable than both corn and wheat baled residue on an energy basis. The reduced feed quality and higher cost of the feed value doesn’t justify the economics of baling and feeding soybean residue for cow-calf producers. From a short-term and long-term soil productivity perspective, including for soil and water conservation, soybean residue removal is not justified for agronomic and economic purposes. Factors such as late harvest delaying baling of corn residue, higher hay prices, and opportunity to sell soybean residue may have resulted in more soybean residue baling this year.
|Baling cornstalks, large round baler
(average 1258 lbs/bale)
|Lifting/moving large round bales with tractor
(average distance 1.54 miles)
eXtension Article. October 24, 2008. “What is the comparison between corn stalk bales, soybean bales and milo stalk bales?”
Nebraska Hay Summary. https://www.ams.usda.gov/market-news/hay-reports
Wortmann, Charles S., Robert N. Klein, and Charles A. Shapiro. 2012. Harvesting Crop Residues. Nebraska Extension NebGuide G1846.
Part 2 of my residue management series focuses on grazing corn residue. We’re blessed in 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.
- Crop Residue Exchange: https://cropresiduexchange.unl.edu
- Crop Residue Exchange Resources: https://cropresidueexchange.unl.edu/resources
- Grazing Crop Residues with Beef Cattle (excellent at explaining portion of crop residue, determining stocking rates, leasing rates, etc.)
- Cornstalk Grazing Cow-Q-Lator (excel spreadsheet guide for lease rates)
- Nutrient Removal by Cows Grazing Corn Residue, November 2018 CropWatch article
- Grazing Cornstalks Rental Agreement Considerations, 2016 Beef Article
- Renting Crop Residue: A Checklist for first-time renters, 2016 Beef Article
- Fillable leases: http://aglease101.org
- Grazing spring-calving cow-calf pairs on cornstalks-a producer’s perspective, November 2018 Beef Podcast
- Drewnoski et al. 2015. Effect of Corn Residue Removal on Subsequent Crop Yields. University of Nebraska-Lincoln Beef Report p 53-55.
- Rakkar et al. 2017. Effect of Long-term Corn Residue Grazing on Soil Properties. University of Nebraska-Lincoln Beef Report. p 50-52.
- Ulmer et al. 2017. Effect of Corn residue Grazing or Baling on Subsequent Crop Yield and Nutrient Removal. University of Nebraska-Lincoln Beef report p 46-49.
- Schmer et al. 2017. Corn Residue Use by Livestock in the United States. Agricultural & Environmental Letters.
With harvest finished or wrapping up, focus has shifted to anhydrous applications and managing residue. Corn residue management has been a topic of discussion for years. Research on this topic has included use of tillage, baling, grazing, and use of products like nitrogen.
Iowa State conducted a three year study evaluating the effects of conventional tillage, no-till, and strip-till on residue breakdown on Bt and non-Bt corn residues. They did this by placing bags of residue of Bt and non-Bt hybrids in the three different tillage systems and evaluated decomposition after 3, 6, 9, and 12 months in a corn/soy rotation. The results showed no significant difference between tillage systems or Bt and non-Bt hybrid decomposition. These researchers also studied the impact of nitrogen applications on corn residue breakdown over two years in no-till. Immediately after harvest, three N rates (UAN 32 percent) of 0, 30 and 60 lb N/acre were applied to corn residue. A specific amount of residue was placed in nylon mesh bags and left in the field for 3, 6, 9, and 12 months, after which residue decomposition was evaluated. The different rates of N resulted in no differences in rate of decomposition. In general, the longer the residue remained in the field, the more it decomposed over time, regardless of N rate. Thus the authors shared that applying N after harvest for residue decomposition was not effective nor economical as soil and air temperatures decreased over time after harvest. They shared that in general, decomposition of crop residue is primarily influenced by soil moisture and temperature which allow for microbial activity.
Last year I wrote a series of articles for my news column and shared them in CropWatch regarding cornstalk baling. A team of Extension Specialists/Educators and USDA-ARS also worked together on a workshop at 2018 Husker Harvest Days on this topic. I’ve received various reactions to these efforts, but my desire is to present the research. My perspective is twofold:
- Better serving farmers/landowners in helping answer your residue management questions via the research available and
- With the high winds, dust storms and vehicle accidents last winter/early spring, could we potentially rethink residue management besides so much conventional tillage for this part of the State?
I’m not saying conventional tillage doesn’t have a place, especially as we think of one-time burial of weed seed. I just wonder if we can help reduce soil loss by utilizing other methods of residue management, perhaps including increased use of livestock grazing and cornstalk baling under the right field situations?
Summarizing the research, cornstalk baling is not for every piece of ground or every situation. From the research, our recommendations are that baling of corn residue should only occur on ground with less than 5% slope that yields 180 bu/ac or more, harvesting no more than 2 tons/acre. Retaining at least 2.4 tons of residue allowed for soil carbon maintenance and retaining more residue also reduced erosion. Every 40 bu/ac of corn results in 1 ton of residue at 10% moisture. Baling on fields fitting the above-mentioned criteria should occur a maximum of every other year in continuous corn or once every four years in a corn/soy rotation (due to reduced residue already present after soybean harvest). The research showed no significant impact on soil properties or soil carbon following those guidelines. Other recommendations would be to use a reduced tillage system in the field where baling occurred and consider planting a cover crop and/or adding manure.
In 239 site-years across 36 studies, corn residue baling resulted in 3% average yield increase where moisture was not limited, most likely due to more uniform stands. The average nutrients found in 1 ton of corn or sorghum residue was 17 lbs of Nitrogen, 4 lbs of P2O5, 3 lbs of Sulfur, 34 lbs of K2O (which due to Nebraska soils being high in K, the value may be 0-50% of this depending on soil test results), and cations equivalent to 30 lbs of lime. There’s also research that suggests less nitrogen is needed the following year going into corn due to the change in the C:N ratio and increased mineralization. So corn residue baling, based on the research, can be an effective way of managing residue without significantly impacting soil properties if done using the considerations mentioned above. Many fields I’ve observed cornstalk baling in the area this year look good regarding these criteria and most took less than 50% residue off the fields.
This year we’ve also seen a large increase in soybean residue baling in this part of the State. I realize it’s mostly being used for livestock bedding. In a future column and CropWatch article, the research regarding soybean baling will be shared in addition to an economics comparison of various residue management strategies. I will also share on grazing research for residue management in a future column.