Monthly Archives: May 2021
Crop Update: Grateful for when the rains were light to break crust and grateful for sunshine this weekend! Hoping weather works out for those who need to finish up planting! For those whose beans were further along, have received comments about crusted soils and lower soybean populations. A general guideline is to leave a field alone if plant populations are greater than 50,000 plants per acre, the stand is fairly uniform, and the field can be kept fairly weed free. I don’t have research going down to 50K, just observation. As you assess plant stands, keep in mind that a gap in one plant row will be compensated by plants in the adjacent flanking rows. They will form extra branches to take advantage of the sunlight. Thus single-row gaps may not be as yield-reducing as you might think, especially in narrower row spacings.
Soybeans greatly compensate for reduced populations by increasing branching. Nebraska On-Farm Research from eastern Nebraska and western Nebraska from 2006-2018 showed only a 1.3 bu/ac yield increase when seeding 180,000 soybean seeds/acre compared to 90,000 seeds/acre in 15-inch or 30-inch rows. (No studies were in sandy soils). Average final plant stands became 154,924 vs. 83,067 plants per acre respectively. Specific examples with lower final plant stands follow:
- A non-irrigated field in Nuckolls County in 2006 was hailed at the cotyledon stage, so planted populations of 100K, 130K, and 160K became average actual stands of 74,417; 89,417; and 97,917 plants per acre with a 4 bu/ac yield difference between highest and lowest plant populations. The average yield in the field was 40 bu/ac.
- A York County irrigated field in 2018 comparing 90K, 120K, and 150K became final plant stands of 60,875, 88,125, and 121,750 plants/acre with yields of 93, 94, and 97 bu/ac respectively.
Every challenge also provides opportunities for learning. So, if you consider replanting, consider leaving some check strips and/or consider an on-farm research study. To do this, consider:
replanting 2 combine widths, skipping 2 combine widths, replanting 2 combine widths, skipping 2 combine widths, replanting 2 combine widths.
It’d be great if you could do that even more often across the field, but just that pattern mentioned above will give you 4 reps that would give you more confidence in the yield results obtained. A Platte County grower did this in 2014. He originally planted 145,000 seeds/acre on May 10 no-till into heavy corn residue. With a plant stand of 75,000 plants per acre, he chose to replant soybeans in strips across the field. He left the original stand and planted an additional 145,000 seeds/acre. Final yields were 58 and 57 bu/ac for the original and replanted stand, respectively. Please let me know if this is something you’re interested in and I’d be happy to help you.
Weed Guide Survey: The Weed Guide has been published since 1960 with over 15,000 copies printed each of the past 5 years. Please consider completing a survey to help us understand the latest trends on how our customers use the weed guide and its value to you: https://ssp.qualtrics.com/jfe/form/SV_1ImdUrOCRmUq9Uy. We really do need and value your input!
Progressive Ag Safety Day June 3: This is a fun-filled day of learning for school-aged children and will be held at the York County Fairgrounds from 8:30 a.m.-1:00 p.m. on June 3. Topics for demonstrations and discussions include: Electrical Safety, Pipeline-Gas Safety, Grain Safety, ATV/UTV Safety, Look-a-Likes, Power Tool Safety, Equipment Safety, and Internet Safety. The registration fee is $5.00. This safety day includes lunch, snacks, a T-shirt, and a take-home “goody” bag. Register with the York County Extension office (402-362-5508). Registration is due by May 25th to ensure a t-shirt and take-home bag; however, please do sign up even after May 25th if you read this after the date! We’d rather have the youth get signed up as this is a great learning opportunity! Contact the York County Extension Office (402-362-5508) or Jason Perdue (402-366-2821) for additional information. We hope to see lots of youth there!
Corn Emergence and Growing Degree Days: For this week’s column, I’m going to share information my colleague, Nathan Mueller, Extension Educator in Saline, Gage, and Jefferson counties wrote in his recent blog post. “Many factors affect corn growth and development, especially early in the growing season. A common question this time of year after corn is planted and some fields have emerged whiles other have not is “How many Growing Degree Days (GDD) does it take for my corn to emerge?” Since corn emergence is directly related to soil temperature (and of course soil moisture), the days to emergence vary especially when one compares early planting dates to later planting dates. The general assumption is 120 Growing Degree Days abbreviated GDD for corn to emerge under favorable conditions. However, we know that some planting practices and environmental conditions can decrease or increase the amount of GDD needed for corn to emerge. We use the GDD calculation for air temperature to estimate how long it will take corn to emerge even though soil temperature is the driving factor.
Growing Degree Days (GDD) or Growing Degree Units (GDU) calculation is determined from air temperature. The corn equation for GDD or GDU = (Daily Maximum Air Temperature + Daily Minimum Temperature)/2 – 50. When the maximum air temperature is greater than 86 degrees, we set the value at 86 in the equation, as the growth rate of corn does not increase much beyond 86. Likewise, when minimum air temperature is less than 50 degrees, we set the value equal to 50 in the equation. The sum of daily GDD or cumulative GDD for corn emergence is approximately 90 to 120 under favorable conditions. As a base line for GDD required for corn emergence, colleagues at the University of Wisconsin report that 125 GDD are required for emergence. Based on research in Iowa, corn typically required 90 to 120 GDD from planting to emergence. This range assumes adequate soil moisture and will vary with planting depth, tillage system, and residue cover.
Research shows some adjustments are needed to help fine tune expected emergence dates based on GDD determined from air temperature. Planting practices that change the amount of GDD for corn to emerge include planting date, depth, and residue cover (view full table of variables at https://cropwatch.unl.edu/growing-degree-units-and-corn-emergence). It takes about 10-25 more accumulated GDD for emergence with early planting dates. Planting deeper than 2 inches will increase the number of GDD to emergence by about 15. More than 75% residue cover increases the accumulated GDD needed for emergence, ranging from 30 to 60 GDD more. Additionally, the soil moisture, soil condition, and soil texture change the needed GDD for corn to emerge. Dry seedbed conditions will require more GDD. Crusted or cloddy soils can increase GDD by 30 more. Heavy textured soils require more GDD than do coarse textured soils. Corn genetics also can affect GDD needed for emergence. Therefore, the amount of accumulated GDD from planting to corn emergence can range easily range from 90 to 200 GDD.
In Nebraska, the U2U tool (https://hprcc.unl.edu/gdd.php) can be used to determine local accumulated GDD based on your planting date. For example, at the tri-county corner of Saline, Jefferson, and Gage counties from May 1 to May 13, we accumulated 114 GDD and the 30-year average is 139. In summary, remember that numerous factors drive corn emergence and assuming a standard 120 Growing Degree Days (GDD) for corn to emerge will not always hold true.”
Tree seeds and leafing out: I’ve been watching silver/red maples and ash trees noticing that some, including one of mine, is very heavy in seed production like what we experienced in 2019. There’s also quite a range in oaks with some leafing out normally and others leafing out rather slowly. I think the seed production possibly is due to the warm March. Information from Ohio State shared that, “Every spring, maple trees produce small flowers that turn into seeds. Normally, a cold frost kills some blossoms, but this year the usual chill didn’t arrive at the right time. More blossoms than usual turned to seed.” Oaks leafing out at different rates could be due to the fact we’ve had a cool April/May and it’s also a survival mechanism to not all leaf out at once. We’ve also been experiencing some oak decline (which is also observed in August when leaves prematurely turn brown), and this can also result in slower leafing out. These are just some thoughts; I really don’t know the answers, just sharing that for those who are asking, I’m also observing this.
Hopefully the rains were a blessing in helping the crops where crusting was a concern, adding moisture to the seedbed, and in activating herbicide. This article reaches people throughout the State, so with some experiencing frost potential as I write this, if rhubarb leaves are not damaged too much by frost and the stalks remain firm, it is still safe to eat. If the leaves are severely damaged or the stalks become soft or mushy, do not eat these stalks. Remove and discard them. New stalks can be harvested and eaten. Rhubarb often develops seedheads following cold temperatures, but this also does not affect eating quality of the stalks. Remove rhubarb seedheads and discard.
This week will share on the results we obtained from on-farm research studies where cover crops were interseeded into corn. In 2019, there were two locations in York and Seward counties (interseeded at V5-V6). In 2020, 6 of 11 locations were conducted via on-farm research in York, Seward, Clay, and Hamilton counties (interseeded at V4). Four of the six locations compared an interseeded cover crop to a check treatment of no cover crop. One location compared two corn populations (27,000 vs. 31,000 seeds/ac) to determine corn yield and cover crop biomass impacts. One location compared using only the middle drill unit to interseed the cover crop vs. using all three drill units between the rows to determine any differences in cover crop biomass.
2019 Results: In 2019, the cover crop at the Seward county location emerged and then died, we hypothesize, due to reactivation of Group 27 herbicide. Thus, no biomass samples were taken. At the York county location, cover crop biomass sampled prior to the first hard freeze ranged from 97-220 lbs/ac. It was good to see successful establishment at both locations and that cover crop growth occurred at one of them. In 2019, there were no yield differences between the corn in the check treatments (241 and 258 bu/ac) vs. cover crop interseeded treatments (241 (N mix), 243 (diversity mix), and 256 bu/ac) at the York and Seward locations respectively, which was also encouraging. Net return was less for the interseeded cover crop treatments vs. the check.
2020 Results: In 2020, cover crops emerged at all locations and grew throughout the season. Cover crop biomass varied by location with the most occurring in fields that were damaged by the July 9, 2020 windstorm (the location with the greatest biomass had 45% green snap). Thus, the open canopy resulted in greater weed and cover crop biomass. Biomass samples were collected in late September by taking three 30” X 30” or 36 X 36” squares for each treatment (dependent upon row spacing). The samples were sorted in the field into weeds, interseeded forbs/legumes, and interseeded grasses and placed in separate paper bags. Samples were weighed and dried. We wanted to compare any differences in weed biomass between the check and interseeded treatments, especially since no residual herbicides were used in 2020. There were no differences in weed biomass between the check and interseeded cover crop treatments. Total cover crop biomass accumulated varied by site and ranged from 277 lb/ac to 3818 lb/ac. It should be noted that the cover crops continued to grow after we sampled until the first hard freeze occurred. The cowpeas provided the greatest biomass and grew to the tops of the tassels. They also formed a ‘bridge’ between corn rows where the canopy broke open. Cowpeas, hairy vetch, sweetclover, and forage soybean were all fixing nitrogen during the 2020 growing season. The red clover and hairy vetch that survived the winter were fixing nitrogen in the spring of 2021.
The windstorm greatly impacted yields as well. Across all the sites, corn yield for the check averaged 214 bu/ac while corn yield for the interseeded treatment yielded 209 bu/ac. At four of the six sites, yield was significantly lower where the cover crop was interseeded. At the remaining two sites yield was not different between treatments. Net return for the corn where the cover crop was interseeded was less at five of the six locations. Net return includes the yield and price of the corn crop and cost of cover crop seed and application. Other than the York county location (two years), all the location data is based on one year of research. These studies will continue in the same fields and strips for at least three years, so it will be interesting to watch for any changes in soil biological and physical properties over time as well. Visually, in the field where the center drill unit vs. 3 was used, it appeared that the 1 drill unit had more biomass. Statistically, it ended up the same as the three drill units for total cover crop biomass. At the York location where cover crops were interseeded into two corn populations, there were no yield differences between the corn populations; however, both yielded less than the check treatment. A special thanks to all the growers working with us on these interseeding cover crop studies and to The Nature Conservancy, Upper Big Blue NRD, NRCS, and Kellogg’s for their partnership with Nebraska Extension on this effort. If you’d like more information, I’ve provided tables of data and links to videos we produced at my blog site jenreesources.com.
Cover crop biomass as a result of interseeding using three drill units (left) vs. only the center drill unit (middle). Close up of Penn State Interseeder drill units (right).
Nebraska On-Farm Research Virtual Field Day Interseeding Videos:
- Interseeding drills: https://cropwatch.unl.edu/interseeding-cover-crops-steve-melvin-june-12-2020
- Interseeding into Soybean: https://cropwatch.unl.edu/interseeding-cover-crops-soybeans-steve-melvin-june-10-2020
- Interseeding studies: https://youtu.be/gQKAGzkweG4
- Interseeding Mixes: https://youtu.be/b64PCMV1pwc
- Interseeding and Herbicide programs: https://youtu.be/5P8tE3oQ7hA
With the challenge of growing cover crops, particularly after corn harvest, interest in interseeding cover crops into living corn and soybean has increased in recent years. Goals for doing so include using the cover to: grow nitrogen for the crop, remove excess nitrogen (in the case of seed corn), aid in weed and erosion control, increase biodiversity, determine any soil health benefits, and desire for fall biomass for grazing. Some are also concerned about increasing regulation and wanting to figure things out ahead of the curve. Planning is key when it comes to interseeding cover crop into corn or soybean. Planning needs to include the goal of why interseed, the cover crop species interseeded, how the cover will be interseeded, the corn/soybean crop development stage for interseeding, and the herbicide program used.
A few years ago, we wrote an article sharing what was known about interseeding cover crops. The following is information we’ve learned as an interseeding project between The Nature Conservancy, Upper Big Blue NRD, Nebraska Extension, 11 farmers, NRCS, and Kellogg’s.
Timing: In corn, we’d recommend aiming for V4 (four leaf collars). V5-V6 is almost too late in years where canopy closure occurs quickly. The literature says there’s no yield loss after V2. For soybean, aerial interseeding around senescence (leaves turning yellow) is one option. From plots interseeded at V4 in 2020, we felt that was almost too late for aiding establishment. This year we will be trying at planting through V2.
Species: Penn State has a mix that’s considered the interseeding standard; it includes annual ryegrass, red clover, and hairy vetch. From the 12 species mixes we tried, the annual ryegrass, vetch, red clover all survived and were growing this spring. Thus, most likely why it’s considered the standard.
In corn, we’ve tried multispecies mixes because of the growers’ and partners’ goals and testing what came through different herbicide programs. We found the first species to emerge were the buckwheat and cowpeas. The farmers liked the species that provided more of an understory like the annual and Italian ryegrass, collards and other brassicas, and buckwheat. Cowpeas grew up to the corn tassels and provided the greatest biomass. Most of the species went to seed. Cowpeas, forage soybeans, and sweet clover were fixing nitrogen in season.
For diversity, the flax and buckwheat upon flowering drew many beneficial insects to the field. Pests like grasshoppers ate the covers in the interseeded strips and left the corn alone from what I observed.
In soybean, wheat was planted in the soybean management field day trials last year with some success. This year we’re considering wheat + red clover for the fields that will be interseeded from planting through V2.
Herbicide Programs: This is the difficult part. I think ideally (and I’m unsure if this is even realistic yet), a cover between rows aiding in weed control, adding nitrogen, providing fall biomass, and regrowing the following spring to aid in weed control again with only needing to add herbicide in a band, would be pretty cool.
In the wet year of 2019, Callisto-type (Group 27) products did their job and kept re-activating. This led to covers dying in one field. So in 2020, I suggested no residuals in post- apps. The guys went with me on this with most doing a pre- with residual followed by a post- of only glyphosate or Liberty prior to interseeding. The July 9th, 2020 windstorm causing plants to greensnap and/or bend caused problems with the canopy opening up and weed control in addition to biomass growth became a problem in these fields in competing with the corn crop. I was just sick about this and the guys extended much grace to me.
This year, for corn, some guys are sticking with last year’s program because it worked well for them, particularly in no-till with heavy residue. Another thing some may try is to apply a pre- with residual, interseed at V4 and then upon 1-2” growth of the covers, apply Dual II Magnum or Outlook (no grazing restriction with Outlook) to provide residual to aid in weed suppression. One farmer who applied generic Lexar pre-plant in some fields and did split app in others in 2020, still saw cover crop growth and emergence from the split applied. The cover crop growth in the split-applied was just stunted and thin compared to the fields where he applied the full rate pre-. He’s testing herbicide programs this year.
For soybean, there’s even more risk. For those who wish to plant and interseed at the same time, we’re trying a burndown immediately prior to interseeding (if they hadn’t applied an early pre- already), allowing the cover to get 1-2” tall and then go with a Group 15 chemistry. The other option we’re trying is going with their pre- with residual followed by interseeding at V2 and application of Group 15 herbicide after cover reaches 1-2” of growth. We also have guys who are planting soybean green into rye and will try interseeding after rye termination. We have no idea how all this will work and if others have ideas, please feel free to share! Next week I’ll share the yield and biomass results from the past few years.
The above pics were post-harvest. The covers showed good at that time still but they seemed to disappear pretty fast upon more hard frosts.
The above pictures were taken in March 2021 of spring growth. Annual ryegrass, hairy vetch, red clover, and collards survived the winter. As time went on, one could easily ‘row’ where the covers were interseeded in June 2020. The taproots on the red clover were extra impressive to me! Also, pretty much always saw earthworms when I dug up one of these plants.