Precision Winter Cereal Rye Cover Cropping for Improving Farm Profitability and Environmental Stewardship

Progress report for LNC20-432

Project Type: Research and Education
Funds awarded in 2020: $249,871.00
Projected End Date: 10/31/2023
Grant Recipient: Purdue University
Region: North Central
State: Illinois
Project Coordinator:
Dr. Shalamar Armstrong
Purdue University
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Project Information

Summary:

Currently, farmer surveys suggest that <5% of row crop acreage in the North Central region of the U.S. receives cover crops. Cereal rye is the most common cover crop in the region because it is winter hardy and provides several environmental ecosystem services. However, reduced yield for corn and occasionally soybean (in wet springs) following cereal rye has been well documented and widely attributed to reduced soil inorganic nitrogen (N) availability. The negative trade-off of reduced yield is a major contributor to the lack of cover crop adoption in the region. Thus, there is a critical need to develop cover crop management strategies that mitigate cash crop yield reductions, while maintaining effectiveness in mitigating nitrate loading through tile-drainage and other ecosystem services. Two viable solutions that we propose to investigate are (1) creating non-intersecting zones of cover and cash crops growth using Real Time Kinematics (RTK) gradience and (2) including a legume cover crop with no-intersecting zones as described in solution 1 to eliminate N immobilization during cash crop growth. Therefore, this proposal will focus on investigating precision planting winter hardy cover crops (WHCC), cereal rye and crimson clover, to minimize the interaction between cover and cash crops through non-intersecting zones established through RTK guidance precision planting of cover crops. The non-intersecting zones of WHCC could reduce N immobilization and cover crop seeding rates, while maintaining nitrate loss reductions and competitive corn yields relative to the no cover crop control. However, there is no research that quantifies potential N credits and the environmental and soil health trade-offs of reducing cereal rye planting density and the inclusion of a winter hardy legume, relative to the conventional density of cereal rye only. We will investigate potential N fertilizer credits and differences in tile-drainage water quality, short-term soil health dynamics, and profitability between the traditional and precision planted WHCC. This study has potential to increase cover crop adoption by equipping North Central region farmers with knowledge to build on common cover crop strategies toward advanced cover crop adaptive management that maintain cash crop yield, reduce nutrient losses, improve soil health with adjusted corn N need, while at potentially lower seeding rates and cost. Our educational approach will focus on conducting on-farm research and associated field days, extension meetings and augmentation of extension cover crop signature programs, develop curricula for training workshops, development of fact sheets and online data visualization platforms, and scientific meetings.

Project Objectives:

Objective: To determine the impact of precision planted WHCC on crop yield, farmer economic risk, and nitrogen loss reduction.

Learning outcomes: The research project will generate knowledge on adaptive cover crop management that would allow WHCC to be precision planted ahead of crops in non-intersecting zones. Precision planted WHCC in strips could inform farmers to lower WHCC seeding rates, adjust the N need for corn crop, while improving soil health, maintaining significant nitrate-N loss reduction via tile drainage and crop yields.

 Action outcomes: Increased adoption of WHCC before corn and soybeans due to competitive agronomic production and less economic risk.

Introduction:

The goals of a Sustainably Intensified Agriculture (SIA) system are to maximize agronomic production, while minimizing environmental degradation. Thus, fulfilling and aligning with all four pillars of sustainability, human, social, economic, and environmental. The demand for increased agriculture production due a growing human population is a reality within the state and globally. On the same scale, there is a need to develop row crop sustainable agricultural systems that can meet the production demand, while not violating the social, economic, and environmental pillars of sustainability is also pressing and critical. Tile-drained row crop agriculture has been identified as a major contributor of nitrogen (N) from the Upper Mississippi River Basin (UMRB) to the hypoxic zone of the Gulf of Mexico. Cover cropping has been identified as the most effective in-field conservation strategy that can be adopted on a large scale to achieve the non-point nutrient loss reduction goals.

 

Cereal rye has become the most commonly selected option for cover cropping because it is well suited for the growing environment of the UMRB region, due to its winter hardiness and wide planting date window that allows for establishment after cash crop harvest. However, a barrier to adopting cereal rye is that it has been found to reduce corn yields due to immobilization of soil available inorganic N. This reduction in available soil inorganic N has been attributed to early season soil N depletion from the soil profile due to N scavenging of cereal rye and N immobilization by the microbial community due to carbon release into the soil profile following cereal rye residue decomposition. Thus, there is a critical need to develop cropping systems that optimize cash crop production and nutrient loss reductions.

 

 

Therefore, we are proposing to investigate precision planted winter hardy cover crops and the inclusion of over wintering legumes. Key assumptions that could be contributing to transformative corn yield when cover crops are precision planted compared to the conventionally drilled or broadcast methods are (i) the creation of non-intersecting zones for cover crop and cash crop growth using RTK guidance. Biologically, non-intersecting zones could result in less cover crop biomass interfaces within the cash crop growing zone, less contribution of carbon, and possibly less N immobilization during peak decomposition of the cover crop biomass above and below ground. Physically, the absence of cover crop residue in the corn growing zone will allow for faster spring warm-up and dry out, fostering an environment for good germination and fast early growth. Biochemically, (ii) with the addition of winter hardy legumes could result in less soil N immobilization in the cash crop growing zone and during cash crop growth, due to N rich residue and thus, low C:N ratio. Additionally, creating separate growing zones for the legume cover crop could allow for a later termination date, significantly more cover crop growth, and potentially a greater and more synchronized N release to the following cash crop and/or supplementing N fertilizer in increasingly common extremely wet seasons to compensate for N losses.

 

Existing Knowledge GAPs: In consideration of the above research efforts, the authors and farmer collaborators of this proposal hypothesize greater potential to advance cropping systems that maximizes cash crop production and profitability, while maintaining cover crop ecosystem services of soil health and nutrient loss reductions through addressing the following gaps in knowledge: No published research that quantifies potential water quality (tile-drainage nitrate loss reduction) and soil health trade-offs of precision planting cover crops, which will reduce the effective soil coverage of cereal rye by approximately 50%. No study has investigated the potential impact of legume cover crop inclusion on water quality (tile-drainage nitrate loss reduction), relative to the conventional method of planting the most common and effective N scavenging cover crop, cereal rye. There is a need to fine tune N recommendation for corn following precision planted cover crops. Current N calculator for North Central region (Maximum Return to N; MRTN) does not account for N changes by either cover inclusion or cover crop management. There is a need to quantify the influence of precision planting cover crops on the rhizosphere soil health, nitrogen availability and N uptake by the subsequent cash crop. No study has investigated the influence of precision planting cover crops on the economic profitability or risk of the farmer. There is a critical need to determine if the positive trends observed on a plot scale in the farmer’s plot studies would translate to the field scale.

Cooperators

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  • Dr. Amir Sadeghpour
  • Dr. Andrew Margenot

Research

Hypothesis:

The authors hypothesis is that (1) precision planted cover crop will product similar cover crop biomass and nutrient uptake; (2) the inclusion of over wintering legumes will advance corn yield relative cereal rye before corn; and (3) overwinter legumes will reduce the nitrogen fertilizer rate for optimum yield by 30 lb/A.

Materials and methods:

NCSARE Figures 3-6 Approach and Methods

Experimental Site

(To achieve Objectives 1-3)

Site Description: The research site is in Lexington, IL, which has been established since 2014. The site is already equipped to individually monitor tiled-drained from 1.6-acre fields. The dominant soil types (90%) in the field are poorly drained and lie within a 0-2% slope and are therefore typical of tile-drained regions of the North Central region.

Description of treatments: The experimental site will consist of 5 treatments that will be replicated three times, Zero Control (no nitrogen, no cover crops); No Cover Crop Control; Conventionally planted Cereal Rye; Precision Planted Cereal Rye Precision Planted Cereal Rye and Crimson Clover mixture (crimson clover dominate). 

Conventionally planted Cover crops will be seeded for each treatment using a RTK guided 15ft drill after cash crop harvest. Precision planted cover crops treatments will be seeded with a 15ft drill with a modified seed bin that ensure 15-inch non-interacting strips of cereal rye and crimson clover after cash crop harvest (Figure 3). This planting system is designed to align zones of heavy residue away from the corn row, but separated cover crop species in the three 7.5inch (cover crop rows planted between the placement of where the corn row would be planted in the spring).  The full cover crop seeding rate will be executed by planting the total mass of cover crop seed recommended for the species of cover crop and 30-50% less seed will be planted for the reduced seeding rate treatments (Designed and led by Ralph Upton and John Pike; Collaborating farmers). Cereal rye will be managed for C:N ratio (C:N ratio <20:1(prior to elongation); aboveground biomass less than 2000 lbs A-1) and will be chemically terminated 2 weeks prior to corn planting (early May) and a week prior to soybean (Mid May) planting. Crimson clover will be managed for N contribution and will be chemically terminated within a week of corn and soybean planting. Cover crops will be sampled in the spring before termination to determine biomass production and total N uptake. All plant samples (cover crop and cash crop) will be dried at 60 C, ground, sieved and analyzed for N and C using a dry combustion method.

Corn and soybeans will be planted (at 32,000 plants A-1 (with a row spacing of 30 inches) and 180,000 plants A-1 (with a spacing of 30 inches using twin rows), respectively. All treatments, except the zero control, will receive the agronomic rate of region in the corn year of the rotation. Nitrogen will be applied in the spring at 2 timings, at planting 20-25% of N and at sidedress 75-80% of N fertilizer will be applied, both as 28-0-0.

Agronomics

Plant N uptake and yield: Treatment impacts on plant N concentrations and N use efficiency will be determined by collecting corn and soybean plant tissue samples at critical vegetative, and reproductive growth stages of both crops (V3, V6, VT, R1, R6) and total N uptake will be calculated on a dry weight basis. Corn and soybean yield will be quantified with a commercial combine and verified using calibration and a weigh wagon. Additionally, grain samples will be collected to determine N removal and calculate partial N balances (Lead: Dr. Armstrong).

Soil inorganic N and soil health measurements: In the spring after cover crop termination and after corn harvest soil samples will be collected from the 0-5 cm, 5-20 cm, 20-50 cm, 50- 80 cm depths and analyzed for organic matter, total N, ammonium and nitrate. All soil samples will be collected from 5 locations within each plot and will be composited to represent the entire field to determine treatment effects on soil N distribution (Lead: Dr. Armstrong).

Four soil health indicators recognized by the USDA NRCS will be assessed as well as a fifth and novel biological indicator of N mineralization at the 0-5cm depth at 3 distances from the crop row across time (V3, VT, and R6 growth stages). The ratio of C:N in microbial biomass and active carbon will be calculated to determine relative C vs N limitation of soil microbes in order to mechanistically explain observed immobilization-mobilization outcomes and N gaps. Soil enzymes will be assayed to explain hypothesized differences in C vs N mineralization dynamics across treatments: β-glucosidase (C-cycling), β-glucosaminidase, (C- and N-cycling), and glycine aminopeptidase (N-cycling) (Lead:Dr. Margarnot). Nested soil sensor measures: In addition to the soil health analysis, real-time continuous in-situ monitoring of soil nitrate and microbial activity will occur in the cash crop plant row using newly fabricated electrochemical ion-selective potentiometric nitrate sensor and a microbial activity sensor (Figure 5). (Lead: Drs. Rahimi and Raghunathon)

 Water Quality: An automated tile water monitoring system will be employed to determine the impact of treatments on NO3-N flow-weighted concentration and loading through the subsurface drainage (Figure 2). Each sample will be filtered and analyzed for NO3-N concentrations, which will be used to determine annual loading (Lead: Dr. Armstrong).

 

Air Quality measures: To determine cumulative soil N2O emissions of treatments, soil gas samples will be collected from early spring (before planting) until after harvest, annually. Emissions will be monitored using the closed, vented chamber methodology widely used in agriculture. Samples will be collected weekly from planting to the R1 growth stage of crops and/or after major field activities or events. Four samples will be collected from each chamber to calculate flux rates by regressing N2O concentrations with a set time period (0, 15, 30, and 45 min). Gas samples will be analyzed using gas chromatography to determine N2O concentrations

(Lead: Dr. Sadeghpour).

Economic Analysis: Net returns to each treatment will be evaluated using a partial budgeting approach. That is, only the costs and revenues directly influenced by the implementation of the cover crop will be considered to determine the net impact on the farm’s profit. Further, agronomic data in concert with economic variables (e.g., crop prices and cover crop costs) will be used to calibrate an economic simulation of the risks associated with each treatment. (Lead: Dr. Thompson)

 Statistical analysis: Data for cover crop biomass, their C and N concentrations, corn and soybean grain yields, grain N concentration, N uptake, and removal, N balance, cumulative NO3-N load, and N2O-N emissions will be analyzed via mixed models (SAS Institute, 9.4, 2017). Normality of residuals will be checked and if the residuals were not normally distributed, data will be log transformed. The fixed effect in the model will be treatment and block will be a random effect. 

Data for average flow-weighted NO3-N concentration, N2O-N emissions (at each sampling date), and soil health indicators at three growth stages will be analyzed using mixed models by year. Cumulative NO3-N load, and N2O-N emissions and soil health indicators over years will be analyzed over time using mixed models with year being considered as repeated statements. When treatment effects are significant, predicted means for each treatment will be obtained and a post hoc comparison will be done. We will use linear regression to determine the relationship between soil NO3–N, moisture, temperature, and N2O-N emissions, NO3-N loss, and between corn yield and N2O-N emissions (yield-based emissions) and NO3-N leaching (yield-based leaching).

 

On-Farm Experiments

(To achieve Objectives 1-3 on-farm)

Site Description: On-Farm experiment 1 and 2 will be conducted for 3 years at two sites each that span both Illinois and Indiana on either glaciated and unglaciated soil to ensure that the treatments will be tested in a variety of soil types and growing environments (Figure 6). 

Description of treatments for on-farm experiments 1 and 2:

On-farm Experiment 1: On-Farm experiment 1 is designed to quantify the impact of cover crop planting method and cover crop species on the optimum N fertilizer rate needed for maximum profitability. Therefore, 6 cover crop treatments will be evaluated:  zero control, no cover control, conventional cereal rye, conventional crimson clover, precision cereal rye, precision crimson clover. Each treatment, except for the zero control, will receive 7 N fertilizer rates ranging from 0 to 250 lbs N/acre in the corn years to determine if a N credit can be quantified. Treatments will be replicated 4 times within a split plot experimental design.

On-farm Experiment 2: On-Farm experiment 2 is designed to determine how cover crop planting methods, cover crop species, and seeding rate impact cash crop yield (corn and soybean) and profitability. Treatments will consist of 12 cover crop treatments: zero control, no cover crop control, conventional planted cereal rye-full rate (full recommended seeding rate), conventional planted crimson clover-full rate, conventional planted cereal rye-reduced rate (50% of the full seeding rate), conventional planted crimson clover-reduced rate, precision cereal rye-full rate, precision cereal rye-reduced rate, precision planted crimson clover-full rate, precision planted crimson clover-reduced rate, rotational (rotation of crimson clover before corn and cereal rye before soybean) precision planted-full rate, rotational precision planted-reduced rate. Treatments will be replicated 4 times within a completely randomized block experimental design.

For all on-farm sites, field plots will be 20ft in width and at minimum 200ft long to ensure the accuracy in harvest using the commercial combine and the use of the farmer’s existing equipment. Additionally, farmer collaborators at each site will assist in the design of the plot layout on their farms to facilitate the experimental design and will lead in executing all cultural practices (plant variety, planting population and date, agronomic N fertilizer rate) associated with cash crop management that are conducive for the cropping system in the region. Cover crop planting, biomass analysis and termination management will be conducted using the methods outlined above in the methods for the experimental site (Lead: farmer collaborators).

Cash crop planting and sampling: Corn and soybean will be planted on 30 inches rows. In the soybean year of the cropping rotation provision will be made for twin row planting of soybeans so that plant population can be maintained relative to 15-inch row spacing. Using the methods outlined above above-ground plant samples will be collected at the R6 growth stage for all on-farm experiments.

Nitrogen fertilizer management: At on-farm experiment 1 sites, 7 N fertilizer rates will be applied in the corn year to investigate the impact of cover crop species and planting method on a nitrogen fertilizer credit. In the corn phase at on-farm experiment 2 sites, no cover crop and cereal rye treatments (full and reduced seeding rates) will receive the full agronomic rate of N fertilizer rates and treatments with crimson clover will receive 30%  (base on pass N credit pass experimentation and literature). Within on-farm experiment 1, the impact of treatments on crop N uptake will be determined by above ground plant sampling at plant maturity (R6 growth stage) using plant sampling methods were outlined in the method of the experimental site section above. Corn and soybean will be harvested using a commercial combine at all on farm sites.

Soil health analysis: In on-farm experiment 1, the influence of cover crop planting method and species will be investigated by systematically analyzing changes in the soil microbial activity and soil N and C cycling over time during the cash crop growing season and at distances away from the cash crop row. Soil health analysis methods are outlined in the methods of the experimental site section above.

Economic Analysis: Key economic variable for both on-farm experiments that offering potential direct reduction in establishment cost are yield, N fertilizer credit, and seeding rate. The economic analysis of the on-farm experiments 1 and 2 will follow the same general framework of analysis described for the Experimental site above of a partial budget analysis for each treatment and an economic simulation to quantify risk.

Statistical Analysis: Data will be analyzed using the same statistical methods outlined above. We will use regression models to determine the economical optimum rate of N (EORN; similar to MRTN).

 

 

Research results and discussion:
Research conclusions:

N/A progress report.

Participation Summary
4 Farmers participating in research

Education

Educational approach:

Currently the results from the bonus year (20/21) of the study have been extended to farmers, trainers, extension specialist/educators, government and state conservation agencies on a regional scale through large farmer meetings and on a national scale through invited research talks a conventions and national meeting.

Presentations 2021 based on 2020/2021 data collections

Armstrong, S. D., Indiana CCA Conference 2021, "Next Generation Cover Crop Management to Increase Cash Crop Production and Advance Water Quality," Indiana CCA, Indianapolis, IN. (December 15, 2021).

Armstrong, S. D., The Nature Conservancy Field Day, "Next Generation Cover Crop Management to Improve Cash Crop Production and Water Quality," Ohio State University. (July 29, 2021).

Armstrong, S. D. , University of Padova, Agronomy Departmental Seminar, "Cover crops impact on nitrogen fate in a tile-drainage landscape," University of Padova, Agronomy Department, Italy. (May 20, 2021).

Armstrong, S. D., American Society of Agronomy Educational Series on Cover Crop Basics, "Next Generation Cover Crop Management," American Society of Agronomy. (March 30, 2021).

Armstrong, S. D., The Wisconsin Agribusiness Classic, "Soil nitrate fate and water quality in tile-drained and sustainable cropping systems," Ohio State University, College of Agriculture and Life Sciences. (January 14, 2021).

Armstrong, S. D., The Wisconsin Agribusiness Classic, "Cover crop and 4R nitrogen management impacts on corn nitrogen nutrition and  yield," Ohio State University College of Agricultural & Life Sciences. (January 12, 2021).

 

Planned Farmer Meetings 

March 24, Central IL Champaign County with NCSARE collaborating Farmer and On-farm research site

March 25, Central IL McLean County at the Lexington IL NCSARE project research site

March 29, Southern IN, with NCSARE collaborating farmer and On-farm research site

Project Activities

Precision Winter Cereal Rye Cover Cropping for Improving Farm Profitability and Environmental Stewardship

Educational & Outreach Activities

17 Consultations
3 On-farm demonstrations
3 Online trainings
2 Published press articles, newsletters
16 Webinars / talks / presentations
3 Workshop field days

Participation Summary:

500 Farmers participated
200 Ag professionals participated
Education/outreach description:

Currently the results from the bonus year (20/21) of the study have been extended to farmers, trainers, extension specialist/educators, government and state conservation agencies on a regional scale through large farmer meetings and on a national scale through invited research talks a conventions and national meeting.

Presentations 2021 based on 2020/2021 data collections

Armstrong, S. D., Indiana CCA Conference 2021, "Next Generation Cover Crop Management to Increase Cash Crop Production and Advance Water Quality," Indiana CCA, Indianapolis, IN. (December 15, 2021).

Armstrong, S. D., The Nature Conservancy Field Day, "Next Generation Cover Crop Management to Improve Cash Crop Production and Water Quality," Ohio State University. (July 29, 2021).

Armstrong, S. D. , University of Padova, Agronomy Departmental Seminar, "Cover crops impact on nitrogen fate in a tile-drainage landscape," University of Padova, Agronomy Department, Italy. (May 20, 2021).

Armstrong, S. D., American Society of Agronomy Educational Series on Cover Crop Basics, "Next Generation Cover Crop Management," American Society of Agronomy. (March 30, 2021).

Armstrong, S. D., The Wisconsin Agribusiness Classic, "Soil nitrate fate and water quality in tile-drained and sustainable cropping systems," Ohio State University, College of Agriculture and Life Sciences. (January 14, 2021).

Armstrong, S. D., The Wisconsin Agribusiness Classic, "Cover crop and 4R nitrogen management impacts on corn nitrogen nutrition and  yield," Ohio State University College of Agricultural & Life Sciences. (January 12, 2021).

 

Planned Farmer Meetings (2022)

March 24, Central IL Champaign County with NCSARE collaborating Farmer and On-farm research site

March 25, Central IL McLean County at the Lexington IL NCSARE project research site

March 29, Southern IN, with NCSARE collaborating farmer and On-farm research site

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.