Victor de Sousa Ferreira - Graduate Student, Department of Agronomy and Horticulture

Highboy Cover Crop Interseeding Project Fall 2024 Updates

Katy Moore — Wed, 02 Apr 2025 18:25:34 +0000

Highboy Cover Crop Interseeding Project Fall 2024 Updates

Katy Moore Wed, 04/02/2025 - 13:25 April 2, 2025

Key Takeaways

Cover Crop Establishment: Its emergence and growth prior first hard frost is tied to decent soil moisture at interseeding time.
Ongoing Project: Highboy Cover Crop Interseeding Project (HiCCIP) is moving to the fourth year with interesting findings on cover crop establishment and soil nitrate concentration.

Introduction

Cover crops are a recognized method for improving soil health by reducing soil erosion, increasing soil organic matter, and improving soil structure. Moreover, cover crops can also improve water quality by capturing excess soil residual nitrate that can potentially leach into the groundwater.

While cover crops are growing in popularity in Nebraska, there are many challenges that limit widespread adoption. One example is the narrow window for cover crop establishment from harvest to first (hard) frost. To address these challenges, the Highboy Cover Crop Interseeding Project (HiCCIP) was initiated by the University of Nebraska-Lincoln in 2022. This is a collaborative effort with the Nebraska Department of Environment and Energy (NDEE) and various Natural Resources Districts (NRDs), including the Lower Platte North NRD, Lower Platte South NRD and the Upper Big Blue NRD. The project aims to address barriers to cover crop adoption and explore their impact on water quality.

Fall 2024 Interseeding

In the 2024 season, 1,100 acres across 11 farmer fields were interseeded at R5.5 corn stage. At R5.5 corn growth stage, plants are approaching maturity with dry leaves permitting sunlight to reach the soil surface, which allows cover crop emergence and growth prior to corn harvest and first hard frost. During the interseeding timing in the fall 2024, the weather did not show rain forecasted, thus the farmers were asked to irrigate at least 0.5-inches after interseeding to secure cover crop emergence and growth. Fields were either broadcast interseeded with cereal rye or a mix of cereal rye, rapeseed and turnip, at a seeding rate of 70 lb/ac.

The project also supplied cover crop seeds for 800 acres across 10 fields drilled after soybean harvest for the fields under the three-year protocol for corn-soybean-corn rotation. The seeds supplied to be drilled after soybeans were winter wheat or mix of cover crops (winter wheat, turnip and rapeseed). R5 Interseeding started on Aug. 25, 2024, and ended Sept. 15, 2024.

Figure 1 shows the location of the on-farm research fields interseeded at R5 corn growth stage and drilled after soybean harvest.

Figure 1. Field locations under Highboy Cover Crop Interseeding Project in 2024.

Preliminary Results — Fall 2024

During fall 2024, cover crop stand counts were collected mid-November from eight out of 21 fields following corn and soybean harvest. The fields in this report were seeded with cereal rye on corn (R5 interseeding) and winter wheat after soybean (drill post-harvest).

The stand count measurements were then converted to percent of living plants per square foot, illustrated in Figures 2 and 3, showing emerged plants (%) at R5 interseeding in corn fields and on drill-seeded cover crops post-harvest in soybean fields. The expected number of living plants for the R5 interseeded fields is 32 plants per square foot at 70 lb/ac seeding rate. For the post-soybean harvest drilled fields, the expected number of living plants is 23 per square foot at 50 lb/ac seeding rate. On the two soybean fields, the highest winter wheat emergence was 90% (Figure 3).

On the corn fields, the highest percentage of emerged seeds was observed at the field F4 with 13% (Figure 2). The low percentage of emerged seedlings at the R5 interseeded cereal rye into standing corn may be due to the drier weather conditions during the interseeding timing in 2024 (August-September). According to the National Weather Service, in 132 years of records, September 2024 in Nebraska was the driest September in history. Thus, cover crop germination and establishment might be negatively impacted due to dry conditions after interseeding if adequate irrigation was not provided.

Figure 2. Cereal rye emergence (%) measured in mid-November after corn harvest.

Figure 3. Winter wheat emergence (%) measured in mid-November on drilled cereal rye post-soybean harvest.

Our team will follow up with spring 2025 cover crop biomass across all sites interseeded at R5 corn growth stage and drilled after soybean harvest to estimate biomass accumulation and collect soil samples for nitrate analysis.

Acknowledgements

We would like to thank our collaborating farmers, the Lower Platte North, the Lower Platte South and Upper Big Blue NRDs for providing their fields and/or technical support for this project.

Funding

Funding provided by the Nebraska Department of Environmental and Energy Nonpoint Source Pollution Program and USDA-NIFA.

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UNL researchers share third year results of the study, which reflect interesting findings on cover crop establishment and soil nitrate concentration.

Victor de Sousa Ferreira - Graduate Student, Department of Agronomy and Horticulture, Chris Proctor - Weed Management Extension Educator, John Nelson - Extension Educator, Jenny Brhel - Extension Educator, Bruno Lena - Extension Educator, Aaron Nygren - Extension Educator, Travis J. Prochaska - Extension Educator

Early Season Interseeded Cover Crops in Corn and the Impact of Residual Herbicides

David Houfek — Sat, 07 Dec 2024 03:46:14 +0000

Early Season Interseeded Cover Crops in Corn and the Impact of Residual Herbicides David Houfek Fri, 12/06/2024 - 21:46 July 24, 2024

Cover crops can increase soil organic matter and fertility, reduce erosion, reduce nutrient leaching and suppress weeds. As a result, they contribute to improving soil health and help ensure the long-term sustainability of cropping systems. These benefits are directly related to production of cover crop biomass. However, in Nebraska there is a short window for cover crop growth between harvest and the planting of the next cash crop. Therefore, early season drill interseeding might be a viable strategy since it extends the window for cover crop establishment and growth.

The use of residual pre-emergence herbicides is an essential weed control tool in corn production because it reduces early season weed emergence, weed-crop competition and yield loss. The residual effect of such herbicides can also reduce, or even prevent, the emergence and establishment of cover crops, emphasizing the importance of choosing an herbicide program that is compatible with early season interseeded cover crops.

To evaluate potential herbicide carryover that could negatively impact cover crop establishment, Bayer and UNL partnered to conduct a study at the Bayer Water Utilization Learning Center near Gothenburg, Nebraska. The goals of the studies were to evaluate cover crop biomass production at (1) different early season interseeding timings in corn and (2) the impact of residual herbicide programs on cover crop establishment.

Figure 1. Hiniker interseeder used to interseed cover crops in between corn rows.

Two different studies were conducted. The first study was conducted on standard stature corn, where both interseeding timing and herbicide program (Table 1) were evaluated. The second study was conducted on standard and short stature corn where only the interseeding timing was evaluated. On both studies, a mix of annual rye (10 lb ac^-1), cereal rye (35 lb ac^-1) and winter wheat (35 lb ac^-1) at 80 lb ac^-1 was interseeded at V2, V4 and V6 corn stage using a Hiniker drill interseeder (Figure 1). Aboveground biomass of the cover crops on both studies was collected at V10 corn stage and dried to constant weight.

Standard Stature Corn — Study 1

In this study, all plots received PRE emergence herbicides at corn planting time. Then, all plots were split, and the POST emergence herbicides were sprayed in one split. Thus, we had treatments with PRE only, and treatments with PRE + POST herbicides. The treatments receiving POST emergence herbicides were sprayed after cover crop emergence to assess possible negative impact on cover crops establishment.

Table 1. Herbicides and rates sprayed over the study as PRE and POST emergence.
Trade Name (Active Ingredient)
PRE	POST
Verdict® (saflufenacil + dimethenamid-P) at 12 oz/ac + Roundup PowerMAX 3® (glyphosate) at 30 oz/ac	Outlook® (dimethenamid-P) at 8 oz/ac
Bicep II Magnum® (s-metolachlor + atrazine) at 67.2 oz/ac + Roundup PowerMAX 3® (glyphosate) at 30 oz/ac	Dual II Magnum® (s-metolachlor) at 1 pt/ac
Harness Xtra® (acetochlor + atrazine) at 73.6 oz/ac + Roundup PowerMAX 3® (glyphosate) at 30 oz/ac	Warrant® (acetochlor) at 48 oz/ac

In this study, the total cover crop biomass production varied depending on the interseeding timing on control plots (no herbicides), as the cover crops were interseeded as the corn growth stage progressed. At V2, V4 and V6 corn stage, total cover crop biomass was 725 lb ac^-1, 499.4 lb ac^-1 and 334.5 lb ac^-1, respectively — shown on Figure 2.

Figure 2. Total cover crop biomass collected from control plots (no-PRE and no-POST) at V10 corn stage of each interseeding timing (V2, V4 and V6). Letters indicate statistical differences (p

The cover crop mix interseeded at V2 corn stage showed greater cover crop biomass than the treated plots with different active ingredients when no PRE emergence herbicide was applied (Figure 3). Moreover, applying saflufenacil + dimethenamid-P or s-metolachlor + atrazine had similar impact on total cover crop biomass.

At V4 corn stage, No-PRE and s-metolachlor + atrazine treatment had similar cover crop biomass production (Figure 3). However, a grower could safely apply any of the PRE emergence herbicides to control weeds in case of V4 interseeding cover crops decision.

At V6 corn stage, all PRE emergence herbicides had similar impact on cover crop biomass, and aboveground biomass of those PRE emergence herbicide treatments were lower than the No-PRE treatment (Figure 3).

Interseeded cover crops at V2 corn stage did not show negative impact when spraying dimethenamid-P as POST application over plot treated with saflufenacil + dimethenamid-P as PRE, compared with treatments spraying only PRE, as shown on Figure 4. Moreover, spraying acetochlor (POST) after acetochlor + atrazine (PRE) or s-metolachlor + atrazine (PRE) also did not show negative impact on established cover crops. Interseeded cover crops at V4 and V6 did not show negative impact on cover crops by applying POST herbicides after PRE emergence herbicides.

Figure 3. Total cover crop biomass collected at V10 corn stage of each interseeding timing (V2, V4 and V6). Letters indicate statistical differences (p

Across all treatments and interseeding timings, the biomass production was statistically equal, meaning it is safe to apply PRE+POST herbicides (Figure 4). However, it is important to highlight that the early interseeding at V2 corn stage might result in satisfactory cover crop biomass production.

Figure 4. Total cover crop biomass collected at V10 corn stage of each interseeding timing (V2, V4 and V6) and on each treatment (PRE only and PRE + POST). Letters indicate statistical differences (p

Standard vs Short Stature Corn — Study 2

On this study, all plots received PRE emergence burndown herbicide, DiFlexx^® (dicamba) at 8 oz ac^-1and Roundup PowerMAX 3^® (glyphosate) at 30 oz ac^-1 at corn planting time.

Interseeded cover crops at the V2 corn stage on short stature corn had more biomass production (1075.6 lb ac^-1) than the cover crops interseeded on standard stature corn (550.6 lb ac^-1), shown on Figure 5. However, interseeding cover crops at V4 corn stage did not have difference between the treatments, with cover crop total biomass of 337.7 lb ac^-1on short stature corn and 367.3 lb ac^-1on standard stature corn. When cover crops were interseeded at V6 corn stage, the short stature corn treatment showed total cover crops biomass production (297.7 lb ac^-1) greater than regular stature corn (189.7 lb ac^-1), shown on Figure 5.

Interseeding cover crops at V2 corn stage on short stature corn showed to be promising compared to interseeding cover crops in standard stature corn. As corn grows, the canopy for both hybrids start to “close,” blocking the sunlight to reach the cover crops on interrow. Moreover, when planting cover crops at late vegetative corn stage — V4 and V6 — total biomass accumulated are less than the total cover crop biomass observed at V2 corn stage on both short and standard stature corn hybrids. Figures 6 and 7 show the difference of interseeded cover crop stand at V2 corn stage on both standard and short stature corn; pictures were taken late July 2023.

Figure 5. Total cover crop biomass comparison into short and regular stature corn collected at V10 corn stage of each interseeding timing (V2, V4 and V6). Letters indicate statistical differences (p

Take Home Messages

Growers can safely apply saflufenacil + dimethenamid-P, acetochlor + atrazine, and s-metolachlor + atrazine when interseeding cover crops despite the biomass reduction when compared to no-PRE herbicides (control), as all PRE herbicides did not kill cover crops.
Applying PRE+POST herbicides did not show negative impact on cover crop establishment, compared with applying PRE only.
Interseeding cover crops early on standard stature corn at V2 corn stage showed more biomass production than the late interseeding timings, at V4 and V6 corn stage.
Short stature corn showed potential of satisfactory cover crop biomass production if interseeding occur early, at V2 corn stage, when compared with interseeding on standard corn stature, shown on Figure 5.

Figure 6. Cover crop stand of V2 interseeding timing on short stature corn. Picture taken in July 2023 at corn stage V10.

Figure 7. Cover crop stand of V2 interseeding timing on regular stature corn. Picture taken in July 2023 at corn stage V10.

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Victor de Sousa Ferreira - Graduate Student, Department of Agronomy and Horticulture, Chris Proctor - Weed Management Extension Educator, Alexandre Tonon Rosa - Learning Center Agronomist, Bayer Crop Science, Mark Reiman - Learning Center Manager, Bayer Crop Science

2024-07-26-cover-crops-herbicides-figure-1-thumbnail.jpg

Interseeding Cover Crops into Soybean in West-central Nebraska

David Houfek — Sat, 07 Dec 2024 04:02:22 +0000

Interseeding Cover Crops into Soybean in West-central Nebraska David Houfek Fri, 12/06/2024 - 22:02 April 3, 2024

Cover crops are increasingly being used as a strategy to promote soil health and farming system sustainability in Nebraska and the United States. Cover crops can provide important ecosystem services such as reduction in soil erosion and nutrient loss, increased nutrient use efficiency, fixation of atmospheric nitrogen (N₂) through symbiosis with legume species, improved soil quality and weed control from residue cover.

Farmers commonly drill cover crops after soybean harvest and sometimes after corn. For corn, there is an opportunity to drill cover crops in between rows via interseeding early season between V2-V6 stage (two to six fully developed leaves) or broadcast cover crop seed late in the season at the R5.5 (full dent) corn stage.

In soybean, cover crops can be drilled after harvest or broadcasted late in the season. Unlike in corn, the interseeding of cover crops into soybean with an adapted drill before R2 stage (full flowering) in 30-inch row spacing setting has not been widely tested. Also, farmers still have questions regarding cover crop water use, variety selection, seeding rate, seeding timing, the negative impact of residual herbicides on cover crop establishment, and the possible impact of the cover crops in the current (soybean) and following (corn) cash crop yield. The objective of this study was to test how interseeding cover crops into soybeans affects soybean seed yield and nutrient dynamics for the following corn crop.

The experiments were conducted in 2022 (soybean) and 2023 (corn) at West Central Research, Extension and Education Center (WCREEC) in North Platte, Nebraska, under central pivot irrigation. Weather conditions and crop sequence during the study are shown in Figure 1.

In 2022, soybeans were planted at 180,000 seeds per acre (30-inch row spacing) on May 19, and cereal rye was interseeded mid-season, July 13, at the R2 stage of soybean. There were two cereal rye seeding rate treatments of 60 pounds seed per acre and 120 pounds seed per acre, and a control treatment without a cover crop. The results of 60 pounds and 120 pounds of seeds per acre treatments were combined and analyzed together, due to no statistically significant difference between these two seeding rates on the variables analyzed. Hereafter, we reference treatments as cover crop (CC) and no cover crop (no CC).

Figure 1. Rainfall (inches), solar radiation (MJ m-2 d-1) and average temperature (°F) in 2022 and 2023. Crop sequence is shown at the bottom of the figure.

The soybean herbicide program included a pre-emergence (May 11, 2022) of 3.5 ounces per acre Fierce^® (Flumioxazin + Pyroxasulfone) and one quart per acre glyphosate, and post-emergence application (June 8, 2022) of Engenia^® (dicamba) at 12.8 ounces per acre and Clethodim at eight ounces per acre.

Cover crop aboveground biomass was collected two times: before soybean harvest (Sept. 27, 2022), and prior to CC termination right before corn planting (April 25, 2023). The soybean was harvested on Nov. 10, 2022, and yield was recorded (Figure 2).

Figure 2. Soybean yield in 2022 (Panel I), cereal rye biomass before soybean harvest and before its termination in 2023 (Panel II), and corn yield in 2023 (Panel III). Letters indicate statistical differences (p

In 2023, corn was planted at 32,000 seeds per acre on May 16. Soil sampling was performed in April before corn planting to assess nutrients, especially nitrogen (N) available for corn. Aboveground corn biomass was also collected during the season to track crop N dynamics on CC vs. no CC situation (Figure 3). No fertilizer was applied to corn during the season to quantify how much N the previous cover crop was providing the corn crop. Corn was harvested on Sept. 11, 2023 and yield is reported in Figure 2.

In 2022, mid-season cereal rye interseeding did not show signs of residual herbicide carryover from pre- and post-emergence application, regardless of the potential residual carryover of Clethodim (300 days in soil with pH 7-8 such as the experimental soil). There is a concern by producers that herbicides can negatively impact cover crop establishment throughout the crop season. However, cereal rye drilled over a month after the post-emergence herbicide application in this study emerged and resulted in a satisfactory biomass production of 613 pounds per acre before soybean harvest (Figure 2 – panel II).

It is worth mentioning that, during soybean harvest, part of this interseeded cover crop biomass was cut by the combine. Thus, if the purpose of the cover crop is for grazing in the fall after soybean harvest, some time for CC regrowth needs to be allowed. On the other hand, more testing with interseeding cover crops into soybean is needed to understand their growth and impact on soybean harvest, as fresh green plant material could impact combine performance and possibly soybean harvest moisture, which was not the case in this experiment.

In this study, the soybean seed yield was not affected by the interseeded cover crop, which is a desirable output considering the cover crop's ability to suppress weeds and produce biomass for grazing or building soil organic carbon pools or capturing payments for utilizing cover crops through climate smart initiatives (Figure 2 – panel I). In April 2023, the cover crop aboveground biomass before termination was collected and it showed total biomass production of 914 pounds per acre (Figure 2 – panel II). The corn yield in 2023 on no CC treatment was greater than the CC treatment, denoting that part of the nutrients were immobilized by the cereal rye interseeded in 2022.

In April 2023, soil sampling was performed before corn planting and our findings show that nitrate content in pounds per acre on no CC treatment across the four depths sampled of 12, 24, 36 and 48 inches was greater than the CC treatment (Figure 3 – panel I). Unlike other nutrients, soil N was largely depleted by the CC treatment in the upper two feet, suggesting cereal rye can capture a decent amount of nitrate surplus in the upper portion of the soil, even with low biomass production. Our measurements indicate that 29 pounds of N per acre in the first foot and 11 pounds of N per acre in the second foot were immobilized in CC in comparison to no CC (Figure 3 – panel I).

Figure 3. Soil samples results prior corn planting in 2023 collected at six-, 18-, 30- and 42-inches depth. Nitrate content in lb ac-1 (panel I), sulfate in ppm (panel II), potassium in ppm (panel III) and phosphorus in ppm (panel IV).

The soil sulfate also showed CC immobilization throughout the soil profile (approximately 13 pounds of S per acre per foot), which implies the need for an integrated and balanced nutrient management when utilizing cover crops (Figure 3 – panel II). Other macronutrients such as potassium and phosphorus did not show significant changes in their soil availability due to the presence of cover crops (Figure 3 – panel III and IV).

The biomass and N dynamics on CC vs no CC denote an offset that was not overcome during the growing season. The biomass and the N content of corn were higher in the no CC condition compared to the CC treatment. This confirms that the cereal rye in the CC treatment immobilized some of the available soil N and did not fully release it to the corn during the growing season. The amount of final N uptake difference between CC and no CC (41 pounds of N per acre) was about the same as the one found immobilized by the CC in the soil (49 pounds of N per acre). Consequently, corn yield decreased by 37 bu per acre in the CC treatment (Figure 2 – panel III). This stresses the need for on-farm experimentation to see whether the CC will affect corn yield (most likely in cases of low N rates) or will capture residual/unused N.

Still, this experiment shows soil capacity to provide N. The corn crop under irrigation with no supplemental N produced 154 and 189 bu ac^-1in the CC and no CC, respectively. This indicates that the soil alone, where the experiment took place, provided the corn crop with 139-170 pounds of N during the growing season, considering that corn uses around 0.9 pounds of N to produce a bushel of grain. Corn yields also would have been higher in this experiment if a hailstorm hadn’t occurred on July 22, 2023.

Figure 4. Corn biomass in lb ac^-1 across sampling dates (panel I) and corn nitrogen content in lb ac^-1 on each sampling time (panel II). The hail event on July 22, 2023 is shown with a black arrow.

Learnings from Interseeding Cover Crops into Soybean

It is possible to interseed cereal rye on soybean interrow up to the R2 stage in west-central Nebraska. However, it is not a recommended practice for the first time establishing a cover crop.
Cereal rye rates of 60 and 120 pounds of seed ac^-1had the same effects. Lower rates than 60 pounds of seed ac^-1should be tested to find the most cost-effective seeding rate.
The interseeded cover crop showed a great ability to retain nitrates and sulfur but did not modify the available phosphorous and potassium in the soil. These results indicate the need for an integrated and balanced nutrient management when utilizing cover crops in the crop sequence to avoid yield penalties due to nutrient competition of cover crop with the following crop.
The immobilized N in the interseeded cover crop was not fully available for the following corn crop in the experimental conditions of no N fertilizer additions to the corn. The continuous use of cover crops may bring nutrients to balance, but the benefits were not observed during the same year.
Some soils in west-central Nebraska can provide a relatively large amount of N (139-170 pounds N per acre) without the addition of N fertilizer. Knowing the soil capacity with an unfertilized plot/strip can help to fine-tune cost-effective N fertilizer rates.

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Victor de Sousa Ferreira - Graduate Student, Department of Agronomy and Horticulture, Eduardo Lago Tagliapietra - Research Scholar, Department of Agronomy and Horticulture, Taiwo Bamidele - Nebraska Extension Intern, Luzviminda Sazon - Ph.D. Candidate, Department of Agronomy and Horticulture, Lucia Bonfanti - MSc Student, Department of Agronomy and Horticulture, Kasey Schroeder - Research Technologist III, West Central Research, Extension and Education Center, Jeff Golus - Research Manager Plant Science, West Central Research, Extension and Education Center, Chris Proctor - Weed Management Extension Educator, Nicolás Cafaro La Menza – Cropping Systems Specialist, Department of Agronomy and Horticulture

soybean-cover-crop.png

Highboy Cover Crop Interseeding Project Fall 2023 Updates

David Houfek — Sat, 07 Dec 2024 04:02:39 +0000

Highboy Cover Crop Interseeding Project Fall 2023 Updates

David Houfek Fri, 12/06/2024 - 22:02 March 28, 2024

Introduction

Cover crops are a recognized method for increasing soil health by reducing soil erosion, increasing soil organic matter and improving soil structure. Cover crops can also safeguard water quality by reducing nitrate leaching.

While cover crops are growing in popularity in Nebraska, there are many challenges that limit widespread adoption. One example is the narrow window for cover crop establishment from harvest to first (hard) frost. To address these challenges, the Highboy Cover Crop Interseeding Project (HiCCIP) was initiated by the University of Nebraska-Lincoln in 2022. This collaborative effort with the Nebraska Department of Environment and Energy (NDEE) and various Natural Resources Districts (NRDs), including the Lower Platte North NRD, Lower Platte South NRD, and the Upper Big Blue NRD, aims to address cover crop barriers and explore their impact on water quality. Information about what we learned in year one can be viewed in this article.

Synopsis of Fall 2022 Interseeding Accomplishments

In 2022, a highboy interseeder (Figure 1) was utilized to interseed cover crops across 2,972 acres in 33 corn fields throughout Nebraska. Each field received a broadcast application of either cereal rye or a mix of cover crops, including cereal rye, turnips and rapeseed, at an average rate of 70 lb/ac.

Most of the fields were interseeded in August, with select fields being interseeded in early September as corn was observed between the R4 and R6 growth stage. Growers were asked to apply at least one application of 0.5-inch irrigation immediately following field site interseeding to facilitate cover crop germination.

Our team collected cover crop stand counts at 19 fields in October 2022. For fields with cereal rye only, stand counts ranged from 20% to 60% of the applied rate of 34 seeds/sq ft (70 lb/ac equivalent). In contrast, fields (n=19) broadcasted with a mix observed an average stand count of 52%.

Figure 1. Highboy Interseeder used in this project.

Fall 2023 Interseeding — Changing the Approach

As we moved into spring 2023, our team noted poor cover crop growth performance for many field sites interseeded during fall 2022. Poor performance was likely attributed to the combined effect of a dry 2022 growing season, following a dry fall and winter. No biomass data was collected during spring 2023.

For more info on the highboy interseeding cover crop project,
click here

In 2023, building upon the insights gained from the previous year's demonstrations, we collaborated with 24 growers to interseed cover crops across 26 fields, covering approximately 3,400 acres, with a base rate of 70 lb/ac. We implemented several modifications to enhance the effectiveness of the HiCCIP demonstrations.

First, we adjusted the interseeding dates based on observations that the early timing of interseeding (fall 2022), when corn was still green and sunlight was mostly intercepted by the canopy, hindered cover crop growth post-germination. In 2023, we started interseeding on Aug. 28, when corn was at R5.5 growth stage. At this stage, corn plants are approaching maturity, and drying leaves allowed more sunlight to reach the soil surface, allowing for better cover crop growth compared to the earlier interseeding dates in 2022.

For the 2023 growing season, on-farm research trials were conducted. Figure 2 shows an example of the experimental layout we used for OFR trials. Experimental layout included replicated check strips with no cover crops, alongside various treatment combinations:

Interseeded × check (no cover crops).
Interseeded × drilled.
Interseeded × drone interseeded.
2x interseeded rate.

Studies were also conducted in two hailed fields. Observations on cover crop stand count, cover crop biomass and soil nitrate content at 0-1, 1-2, and 2-3 feet will be collected across the treatments in each field. Grain yield data to evaluate yield impact will be collected during the fall of 2024.

Figure 2. Example of a collaborators’ field showing fall cereal rye establishment, check strips, and on-farm research area.

Fall 2023 Interseeding Preliminary Results

Figure 3 shows preliminary stand counts for 13 fields interseeded during fall 2023. Stand count is presented as a percent (%) of plants emerged, which is the total emerged plants relative to the total number of seed planted. For example, the expected number of cereal rye plants is 34 per square foot at 70 lb/ac, and the counted emerged living plants was 17 plants per square foot, therefore emergence rate is 50% (17÷34). Values ranged from 1% to 84% with an average of 27% emergence rate for the fields interseeded with cereal rye. The emergence rate for the fields interseeded with the cover crop mix ranged from 16% to 77% with an average of 41%.

Figure 3. Emergence rate measured from mid-October to early November for cereal rye and mix of cover crops at fields interseeded during corn growth state R5.5. Black bars are the average among all fields for the cover crop selection.

Although the cover crop emergence rate observed during fall 2023 was similar to those found during fall 2022, the later interseeding date and stand count assessments in 2023 resulted in a stand count that was not negatively affected as observed in 2022. To demonstrate that, Figure 4 shows a picture taken on Nov. 11, 2023, about 10 days after corn harvest. We observed that the cover crops were well established. During late fall 2022, however, little to no cover crop establishment was found (visual assessment).

Moving forward into spring 2024, our team is going to assess cover crop biomass and stand count at the same locations as fall 2023. Additionally, we plan to conduct soil sampling to evaluate any changes in soil nitrogen levels during the cover crop season.

Acknowledgements

We would like to thank our collaborating farmers, the Lower Platte North, the Lower Platte South, and Upper Big Blue NRDs for providing their fields and/or technical support for this project.

Funding

Funding provided by the Nebraska Department of Environmental and Energy Nonpoint Source Pollution Program and USDA-NIFA.

Figure 4. Cereal rye interseeded on Aug. 30, 2023. Picture taken on Nov. 11, 2023.

On-Farm Research

Highboy Interseeded Cover Crops

Seeding Practices

Cover Crops

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The Highboy Cover Crop Interseeding Project (HiCCIP) began in 2022 to address cover crop barriers, such as the narrow window for cover crop establishment from harvest to first (hard) frost.

Cover Crops

Highboy Interseeded Cover Crops

On-Farm Research

Seeding Practices

Soil Health

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Soil Health