Improving Cereal Rye Cover Crop BMPs to Increase Adoption of Cover Crops by Iowa Farmers

Oct 2018


The Iowa Nutrient Reduction Strategy calls for cover crop implementation on over 12 million acres. Despite numerous environmental benefits associated with cover crops, many farmers still are hesitant. Major barriers to introducing cover crops as a conservation practice include cost of implementation, yield drag, and knowledge.


Develop BMPs for cover crops through an improved understanding of the effect of seeding rate, seeding method, and termination date of cereal rye on cover crop biomass accumulation, soil temperature and soil moisture at corn planting; corn growth and development throughout the growing season; incidence, severity and prevalence of insects, diseases and weeds, respectively; crop nutrient uptake and soil nutrient dynamics; and soil biological health indicators. Compare the return on investments among treatments through partial budgets. Survey Iowa farmers planting cover crops to determine the most common methods of seeding among cover crops users, and perceived efficacy of seeding methods among those who do not use them.


A field study will be planted at the ISU Ag Engineering and Agronomy Farm, and supplemented with data from smaller studies at two outlying research farms. Cover crops will be planted in fall 2018 and 2019. Most data collection will occur in the summers of 2019 and 2020. Information will be collected on the effect of cereal rye seeding rate, seeding method and termination date on cover crop biomass production, corn growth and development, disease, insect and weed management, nutrient loss and recycling, soil health, and return on investment. This data will be used to develop improved BMPs for incorporating a cereal rye cover crop into corn production.

Project Updates

Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.

July 2022


Key Research Questions

The goal of this proposal was to develop best management practices (BMPs) for including a cover crop in a corn-soybean production system in Iowa for “hesitant” farmers. We evaluated the effect of cover crop seeding rate, seeding method, and termination timing on corn production, soil health and nutrient recycling.

Rsearch Findings

A 2-year field experiment was conducted at three locations in Iowa investigating the effect of two seeding methods, three seeding rates, and two termination timings (one location only) of CR on CR biomass and corn growth, root disease, and yield. Cereal rye biomass and corn growth and development were not affected by seeding rate but by seeding method and termination timing. Broadcast CR produced an average of 3.5 times more biomass than the drilled CR however, this was likely a function of seeding date. Broadcast CR was seeded at least 4 weeks before drilled CR and thus had better establishment in Fall. Use of early maturing soybeans would allow CR to be drilled earlier in the Fall which would allow better establishment. Cereal rye when terminated late (3 days before planting [DBP]) produced 2.1 times greater biomass but 4.1% less corn yield compared to early termination (14 DBP). In general, greater root rot incidence and more Pythium clade B were detected in corn seedlings sampled from broadcast CR than drilled CR. Moreover radicle rot incidence of corn was greater in the late-terminated plots in 1 year. Corn yield was 7.2% less in broadcast CR compared to the drilled CR which was likely because of the greater biomass produced by the broadcast CR. The data from the six location-years in Iowa were used to estimate private net returns to cereal rye across alternative scenarios in a partial budget framework. Net returns in the absence of grazing averaged -$123.74 ha-1 and were negative for 82.2% of the treatments, while net returns under partial grazing averaged -$15.24 ha-1 and were negative for 54.8% of the treatments. Early-broadcast cereal rye produced higher biomass and larger net cost savings in the livestock enterprise than late-drilled cereal rye, but it also resulted in higher corn yield penalties. In the no-grazing scenario, net losses for early-broadcast cereal rye were $165.97 ha-1 larger, on average, than for early-drilled cereal rye We summarized data collected by the Iowa Department of Agriculture and Land Stewardship (IDALS) among farmers who had received technical assistance and/or cost share related to cover crops over the period 2015-2020. The most prevalent types of operations in the survey were farms producing row crops and cattle and farms producing row crops but no livestock. On average, 60% of the respondents were operator-owners of the acres in cover crops. Most respondents seeded cover crops on erodible land, and only on a portion of their fields. About a third of the respondents used cover crops as supplemental feed for their livestock. Eighty-one percent of the respondents planted winter hardy cover crops. Drill planting after harvest was the most prevalent planting method. Seventy-two percent of the respondents terminated the cover crops with herbicides and no-till planted the next crop. The stated motivations to use cover crops reported by at least two-thirds of the respondents include preventing soil erosion, building soil organic matter, improving soil health, and improving/protecting water quality. The most common source of information on cover crop management among respondents was some type of government agency, although the preferred method of receiving information was through discussions with other farmers.

Project Activities

6 presentations

Publications / Journal Articles

Singh, S., A. Plastina, and J. Arbuckle. 2022. "Cover Crop Practices in Iowa 2015–2020." Staff report 22-SR 119. Center for Agricultural and Rural Development, Iowa State University.


Marcos, F.M., Acharya, J.A., Parvel, R., Robertson, A.E. and Licht, M. 2023. Cereal rye cover crop seeding method, seeding rate, and termination timing effects corn development and seedling disease. Agronomy Journal 1-17 doi/10.1002/agj2.21306 Plastino, A., Marcos, F.M., Parvej, M.R., Licht, M.A. and Robertson, A.E. Does Grazing Winter Cereal Rye in Iowa, USA, Make It Profitable? Renewable Agriculture and Food Systems (Accepted pending revision).

Leveraged dollars

Can Adjustments to Nitrogen Rates Reduce Corn Yield Drag and Disease Implications Following a Cereal Rye Cover Crop. Iowa Nutrient Reduction Center. $181,000

Getting to the ROOT of the corn yield drag following cover crops: a cereal rye residue manipulation experiment . USDA-NIFA-AFRI- Foundational Knowledge of Agricultural Production Systems.  $649,000

Total award amounts $ 830,000


July 2021

During Jan. to June 2021, researchers worked on analyzing data and preparing manuscripts for publication.

Other outreach/accomplishments included  4 field days and 6 presentations.

June 2020

Spring and early summer activities were done at all three locations despite the inconvenience of Covid-19. Data are being captured and will be analyzed later this year. Cover crop biomass sampling was done prior to termination at 14, 7 and 0 days before termination (DBT). Soil samples were collected at 0DBT. Lab processing of biomass (drying, weighing and grinding for AgSource) and soil samples has been done.

Cover crops were terminated as planned - 14 days before planting at the ISU Northwest Research Farm NWRF and ISU Southeast Research Farm (SERF), and 14 and 2 DBP at Sorenson Farm near Boone. Plots at all farms were scouted for insect activity prior to and after termination of rye. Corn was planted 1, 4 and 13 May at SERF, Sorenson and NWRF respectively Soil sampling was done at VE (only for Sorenson Farm plots), V2 (all except Sutherland) and V6 (only Sorenson Farm plots). All plots received a side-dress application after soil sampling (V2 timing) Corn seedlings were sampling at V2, and V6 at all locations for biomass measurements. Corn seedlings were sampled at V3 for seedling vigor and disease measurements. V3 seedlings shoot and root tissues were separated and stored for the lab processing for the nutrient analysis and pathogen quantification.

Preliminary results from 2019 include: Cover crop biomass at termination was greatest in broadcast treatments compared to the drilled treatments. CC biomass in the low seeding rate was less than that in the medium seeding rate, which was equivalent to the high seeding rate. Rye biomass affected corn growth; Yield of corn was greater in the drilled rye treatments compared to the broadcast treatments. No effect of treatment on weeds, disease or insects - possible due to low rye biomass in all treatments Winter rye cover crop (CC) decreased soil nitrate at 0-15cm depth (0-6 inches) from -28 to -50% in broadcast, and +2 to -25% in drilled plots, compared to no CC. Nitrate leaching through the soil profile was decreased by -1 to -50% compared to no CC. Plant root simulators, or ion exchange resin membranes, showed little difference between CC treatments and control.

A preliminary economic analysis based on several assumptions suggested that only 3 of the 33 site X treatments showed a positive return. Researchers are collaborating with Iowa Ag to include a couple of questions on their Cover crop survey regarding cover crop seeding rates used.

Other activities included one field day and two presentations.

December 2019

Mid-season and end-of-season corn growth data were collected. In general, broadcasting had more of an effect on corn growth than drilling. This is likely because the broadcast treatment had more cover crop biomass. N sensors were removed from the trial at Sorenson and data collated. Analysis and interpretation is in progress.

Data from membranes used to measure soil nitrate and other nutrients available to corn seedlings in early growth were quite variable, so will not be used in 2021. Although data from resin cartridges was also variable, this technology is cheaper and will be used again in 2021 with some modifications.

At Sorenson, a strong effect of seeding rate on microbial biomass was observed in the broadcast treatments. Due to low cover crop biomass in the tilled treatments, microbial biomass was not assessed. No effect of cover crop treatments was detected on weeds or insects. Most likely because of the very low cover crop biomass accumulation.

Disease data were analyzed. At all locations, greater radical and seminal disease incidence occurred in the broadcast treatments compared to the tilled treatments. Even so, disease severity was very low. At Crawfordsville and Sorenson, corn shoot and root weight at V3 and yield was less than that of the drilled treatments. No effect of seeding rate or method was detected on populations of Pythium clade B or clade F in corn roots.

Economic analysis is in progress. Researchers partnered with IDALS on its cover crop user survey. Data on crop cover crop seeded into, type of cover crop, acres planted /cost shared, timing of seeding and method used are already being collected. In 2020, data on seeding rate will also be collected. Cover crop treatments were planted in September/October, and resin cartridges installed in specific plots at Sorenson.

December 2018

Broadcast cereal rye treatments were planted in mid-September 2018 at all locations. Drill-seeded cereal rye treatments were planted October 29 in Ames, October 22 2018 in Sutherland, and October 26 in Crawfordsville. Note: This is later than usual as soybean harvest was delayed due to above-normal precipitation in September.

The McDaniel lab installed resin lysimeters in plots at the AEA farm location on 25 October 25. No resin lysimeters were installed at NWRF and SERF.

Stand counts were taken in plots the mid-November at all three field locations. Drill seeded rye at all locations had not emerged so stand counts and biomass were not evaluated. Stand counts in the broadcast treatments ranged from ~280,000 to 720,000 plants/acre in the low seed rate treatment (target of 1,000,000 PLS/acre) to 480,000 to 1,800,000 plants/acre in the high seeding rate treatment (1,670,000 PLS/acre).

PIs Arbuckle, Licht and Robertson met in December to discuss the proposed survey of farmers regarding seeding rates and seeding methods. IDALS recently conducted their own survey collecting this data, and it was decided to collaborate with them. They will share their data, which researchers will analyze and summarize.

September 2018

  • Two staff and a graduate student have been placed on the project 
  • All collaborators met in July to discuss procedures and data that need to be collected. 
  • Field locations for the trials were identified at the ISU Northwest Research and Demonstration Farm, Sutherland, Iowa, the Ag Engineering Agronomy Research Farm, Boone, Iowa, and the Southeast Research and Demonstration Farm, Crawfordsville, IA. 
  • Plot layouts were generated and Elbon cereal rye secured. 
  • Broadcast cereal rye treatments were planted in mid-September at all locations. Drill-seeded cereal rye treatments will be planted soon after soybean harvest, which was delayed due to above normal precipitation in September.
  • The McDaniel lab prepared resin lysimeters for installation after soybean harvest.