Corn Management Following Cereal Rye Cover Crop with Strip Tillage and In-Row Fertilization
Cover crop adoption is a key practice promoted to reach the Iowa Nutrient Reduction Strategy (INRS) goals of 45% nitrogen and 29% phosphorus reduction in surface waters. It is estimated 12 million acres of cover crops are needed in Iowa to meet INRS goals, yet only 720,000 acres were planted in 2017, about 3% of the corn and soybean acres planted in Iowa annually. Farmer evaluations show corn yield drag and poor return on investment are the biggest barriers to adoption. Most cover crop research for corn production systems is focused on the management of the cover crop. This research focuses on management of the corn crop following winter cereal rye.
Evaluate the effects of a winter rye cover crop-free zone and starter fertilizer to improve seedling vigor and eliminate yield drag associated with winter cereal rye. This objective will be reached by determining treatment effects on corn growth and development throughout the growing season; disease, insect and weed incidence, severity, and prevalence; and winter cereal rye biomass growth and nutrient uptake.
This project includes a field trial at the ISU Agricultural Engineering and Agronomy Farm, supplemented by companion trials at one outlying research farm. Eight treatments will be used. Cover crops will be broadcast seeded in the fall, and terminated 10-14 days ahead of corn planting for all treatments. Cover crop biomass and nitrogen uptake will be determined with two fall and two spring biomass sampling periods each year. Corn growth and development will include stand establishment; root and shoot biomass, nutrient uptake, and staging at approximately 10 and 20 days after emergence; date of silking and physiological maturity; and grain yield and moisture at harvest. Corn roots will be evaluated for root rot pathogens, and stand establishment observations will be used to detect noticeable seedling death. Insect incidence and weed density/community notes will be determined in every plot. These data will help researchers develop improved management recommendations for corn production following winter cereal rye cover crops.
Highlights of findings, include:
Cereal rye growth
- In the 3 sites-years where there was a no-tillage/strip-tillage comparison, strip-tillage had a 24 to 45% reduction in cereal rye biomass at the time of termination.
- Cereal rye biomass treatment differences were not determined for starter N rates because no starter N was applied at the time of cereal rye termination.
Corn growth and development
- Starter N rates only affected early season corn plant density at 1 site-year (Kanawha 2020 where the 35 and 70 # N/ac starter rate had lower plant densities than the no rye and 0 # N/ac starter rate; p-value = 0.0479). However, the late season, pre-harvest corn plant density had no statistical differences for all treatments for all site-years.
- While not significantly different, the 0 # N/ac starter rate had a 5% reduction in plant height compared to the others starter rates for both site-years. Strip-tillage had an average 5% taller plants than the no-till for both Kanawha and Ames, however, they only differed statistically in Ames (p-value = 0.0511).
- In Ames for both years, the tillage and starter nitrogen treatments had statistical differences for corn biomass until VT/R1. In 2019, the check and 0 # N/ac were similar to each other and statistically inferior to the 35 and 70 # N/ac, while in 2020, only the 0 # N/ac was inferior.
- Strip-tillage always resulted in higher biomass for all sampling times. In Kanawha 2019, starter N treatments had a statistical difference only at VT/R1, with 70 # N/ac having more corn shoot biomass than other treatments. In 2020, the first sampling at V2/V3 had a statistical difference between starter treatments with the check and 0 # N/ac being similar between each other and statistically inferior to the 35 and 70 # N/ac. Tillage treatments were statistically similar throughout the season.
Pest incidence and severity
- Significant effects between tillage methods (no-/strip-tillage) were detected for radicle and seminal disease incidence. Disease incidence was lower in corn seedlings sampled from strip-tillage plots in both radicle and seminal roots. Mean radicle and seminal root disease incidence from strip-tillage plots were 23.1% and 14.0 % compared to 29.3% and 20.0 % from no-tillage plots respectively. However, tillage method had no effect on the severity of root disease assessed visually.
- Similarly, the effect of starter N rate was detected for radicle disease incidence and severity and seminal disease incidence. In general, root disease incidence and severity were greater in seedlings from rye plots regardless of different starter nitrogen rates applied to no-tilled or strip-tilled rye plots compared to check (i.e. no rye, no starter) plots. In general, greater root disease was observed in seedlings in all treatments sampled in 2020 than in 2019.
- Weed suppression effects from the treatments were not detected, most likely because of the robust nature of the herbicide program used. Additionally, insect presence was minimal to non-existent for all site-years. To gain knowledge on insect pressure due to cover crops, it is suspected that larger plot sizes or on-farm studies will need to be conducted.
Corn grain yield
- In 1 of 3 site-years strip-tillage had a 11.4 bu/ac yield advantage over no-tillage. In the other 2 site-years, there was not a yield difference, but overall yield levels were suppressed due to drought and derecho.
- In Ames 2019, the 70 # N/ac starter N rate had a 23.9 bu/ac lower yield compared to the no rye, no starter check. The 0 and 35 # N/ac starter treatments also had higher corn yields than the higher 70 # N/ac starter treatment.
- While not significantly different, Ames 2020 and Kanawha 2019 had similar trends in that the 70 # N/acre starter rate was the lowest yielding. There was not a cover crop or starter N response at Kanawha 2020.
Other activities and accomplishments:
4 field days, 9 presentations, 1 workshop
For the 2020 growing season, cover crop plots were broadcast seeded with Elbon cereal rye at Kanawha (6 October 2019) and Ames (5 October 2019). The fall strip-tillage treatment occurred at Ames (4 November 2019), however, because of wet weather strip-tillage at Kanawha has been delayed to 10 April 2020. Corn planting occurred on 4 and 15 May 2020 at Ames and Kanawha, respectively.
For the 2020 growing season, crop growth and development, disease incidence, weed community and insect incidence were collected as planned through the end of June. Due to COVID-19, some data collection was minimized at Kanawha due to social distancing restrictions affecting travel. Observationally, weed and insect incidence was very low and there were no differences between treatments in 2020, similar to the 2019 year. However, cover crop biomass was much greater than the 2019 growing season, even though fall growth was very low. This can be attributed to breaking of spring dormancy about 1 month earlier and much warmer weather in March and April of 2020 compared to 2019.
No tillage effect was detected for radicle and the seminal disease from both locations. Disease severity was higher in seedlings that received higher (70#) and medium (35#) of nitrogen but it was not different from no (i.e. 0#) nitrogen treatments. Seedlings from check plots (no rye, no starter nitrogen) showed significantly less disease than seedlings following rye regardless of nutrients added.
Outreach included 1 field day and 1 presentation.
For the 2019 growing season, crop growth and development, disease incidence, weed community and insect incidence were collected as planned. Data is being summarized and will be discussed at a project meeting in early 2020. Preliminarily, seedling disease, insect presence and weed populations were not significantly different between strip-tillage and starter N treatments. In fact, disease, insect and weed pressure was found to be at very low levels. This comes as no surprise because cover crop biomass was very low following drill seeding in the fall of 2018 (no biomass samples were taken).
There were corn grain yield differences between treatments. At Kanawha, the no-rye and no starter N check and cereal rye, and no starter N treatments had similar yields (mean of 184 bu/ac) which was higher than the cereal rye treatments with 35 and 70 lbs N/acre (mean of 171 bu/ac). At Ames, the no-tillage treatments averaged 11.5 bu/ac less than the strip-tillage treatments. Additionally, the cereal rye with 70 lb N/ac was the lowest yielding treatment by nearly 25 bu/ac.
For the 2020 growing season, the cover crop plots were broadcast seeded at Kanawha and Ames the first week of October. The fall strip-tillage treatment occurred at Ames Nov. 4, 2019. Wet weather delayed strip-tillage at Kanawha to spring. Fall 2019 cover crop growth was determined at both locations via stand counts and biomass collection in early November.
Outreach included 2 field days and 2 presentations
Plots were laid out, and cover crops were drilled seeded Oct. 19, 2018, in Ames and Oct. 30, 2018, in Kanawha. Cover crop seeding and lack of fall biomass and stand counts collection was due to cold, wet fall conditions, delayed soybean harvest and lack of cover crop emergence. Cover crop biomass, stand counts and soil samples were collected in the spring of 2019 as planned. Cereal rye was terminated on 5/3/19, however, soybean planting was delayed by rain that continued through 5/16/19. This resulted in a longer time frame between termination and planting than intended. Soil sampling, corn biomass and stand counts, crop reflectance, disease, insect and weed assessments were conducted as planned.
Cover crop plots were seeded at Kanawha (October 30) and Ames (October 29). The fall strip-tillage treatment occurred at Kanawha and Ames (November 16). Soil samples were taken for baseline fertility at the Ames site (November 16). No soil samples were collected from Kanawha because of wet conditions followed by frozen soil. Neither site had cover crops emerge so fall cover crop biomass and stand counts were not able to be determined.
A post-doc has been placed on the project. The field locations have been identified at the ISU Northern Research and Demonstration Farm, Kanawha, and at the Ag Engineering Agronomy Research Farm, Boone. Plot layouts have been generated and Elbon cereal rye has been secured. The cereal rye will be drill seeded-soon after the soybean are harvested; weather permitting by mid-October.
The project was discussed at a September 2018 field day at the ISU Southeast Research and Demonstration Farm, Crawfordsville.