Interest and utilization of cover crops continues to grow due to benefits including reduction of soil erosion, managing soil moisture, weed suppression, and increasing long-term soil productivity. It would be useful for North Dakota farmers to have NDSU recommendations from in-state field research, for proper seeding rates of rye based on fall establishment dates, and their goals of using rye as a cover crop prior to soybean production. Study 1 is within the scope of ND Soybean Council agronomy research program priorities: Alternative weed control methods and soil health concerns.
Fertilizer supply and prices, including phosphorus (P), are a major issue for 2022 and beyond. A P fertilizer use option is a preplant P application for corn at rates to allow adequate plant nutrition for soybean the following year. NDSU Extension’s current suggestion regarding this strategy is based on other land-grant university information. Data from Study 2 will address this lack of ND research.
Data from both studies will be shared with ND farmers and crop advisers to improve soil productivity and plant nutrition, while potentially increasing profitability of soybean production.

*Study 1. Conducted at the CREC, will continue examining winter rye fall seeding rate and date combinations:
1. Measure rye plant population and ground cover, soil moisture levels, and weed suppression during the following soybean production period.
2. Measure soybean response to the rye treatments.
*Study 2.
1. Conducted at the CREC and NCREC, will measure soybean response to prior-year P application (for corn and soybean crops) compared to preplant P application during year of soybean production.

The two field studies will aid in providing research-based recommendations:
* Study 1 - Target rye stand density, based on producer goals with the cover crop, while maintaining soybean yield.
* Study 2 - Potentially increase efficient application and use of P for soybean production.

Update:
Winter Rye Cover Crop Establishment Options and Soybean Response to Prior-Year Phosphorus Application
Greg Endres, Mike Ostlie and Leo Bortolon

Objectives of the research:

1. Winter rye seeding dates and rates: Identify optimum rye plant population based on combinations of fall seeding date and rate with rye as a preplant cover crop preceding soybean based on impact on soil factors, weed control, and soybean yield.
2. Response to prior-year application of phosphorus fertilizer: Examine soybean response on low-phosphorus (P) testing soil to preplant, broadcast-applied P fertilizer the prior year for corn plus soybean versus an annual application for corn followed by soybean.
Completed work:
• Trial 1: Fourth year of the study was conducted at the Carrington Research Extension Center (REC). Treatments: Winter rye was seeded on September 22 and October 8, 2021 at 25, 50 and 75 lb/A (six treatments). Rye was terminated with glyphosate June 3, 2022; and soybean planted June 6 and harvested October 3.
• Trial 2: Second year of study (2022 soybean data collected) conducted at Carrington and North Central (Minot) RECs. P soil analysis: Carrington=low (4 ppm) and Minot=8 ppm (medium). Treatments: 1) untreated check, 2) P fertilizer applied for corn (2021) followed by P application the following year for soybean (2022), 3) P preplant applied in 2021 for corn plus soybean. P fertilizer was applied as 0-46-0 (triple superphosphate) based on NDSU Extension recommendations for low-testing soils for corn and soybean production: Carrington=78 lb/A corn and 26 lb/A soybean; Minot=52 lb/A corn and 39 lb/A soybean (actual P).
Preliminary results:
• Trial 1: Rye plant density and ground cover measured during May (prior to soybean planting) ranged from 187,170 to 1,003,920 plants/A and 6 to 21%, respectively, among combinations of rye seeding dates and rates. The greatest rye plant density resulted from planting late at the 75 lb/A seeding rate. Topsoil moisture was similar among rye treatments at soybean planting. Green and yellow foxtail control (80-89%) one month after soybean planting was similar among treatments. Soybean plant density and development, and seed yield (trial average = 72.1 bu/A) and quality generally were similar among treatments.
• Trial 2 (2022 soybean):
o Carrington - Soybean plant development (emergence, flowering and maturity), stand and canopy ground cover generally were similar among the three treatments. Soybean seed yield was statistically (LSD 0.10) similar among treatments: 1) untreated check=43.3 bu/A; 2) P corn/P soybean=45.1 bu/A; and 3) P corn + soybean=45.9 bu/A. Averaged across 2 years (2021-22) on low-P testing soils at Carrington, soybean yield also was similar among treatments: 1) 30.8 bu/A; 2) 33.8 bu/A; and 3) 34.0 bu/A. Also in 2022, test weight and seed count were similar among treatments. Seed oil was reduced but protein increased with sequential-applied P versus prior-year total P application.
o Minot – Soybean yield, test weight, and seed protein and oil were similar among treatments.

Work to be completed:
• Research reports will be written and shared with audiences using Carrington and North Central REC publications and websites, and ND Soybean Council 2022 annual research report.
• Data slides developed and presented for farmers and crop advisers during 2022-23 winter meetings and summer tours.
• The P fertilizer study at Carrington will continue in 2023 on very low-P testing soil (2 ppm). P fertilizer treatments were imposed for 2022 corn and will be applied in 2023 for soybean data collection.

View uploaded report

Update:

View uploaded report

Update:
Winter rye cover crop establishment options and soybean response to prior-year phosphorus application

Background and Objectives of the research:

1. Winter rye fall seeding dates and rates: Farmers that use rye as a cover crop preceding soybean require recommendations on fall seeding dates and rates to meet goals including soil management and other benefits. The study objective is to determine appropriate rye seeding rate and established stand preceding soybean production including ground cover, soil moisture, and weed suppression with rye.
2. Response to prior-year application of phosphorus (P) fertilizer: Study objective is to examine soybean yield response on low-P testing soil to preplant, broadcast-applied P fertilizer the prior year for corn plus soybean versus an annual application for corn followed by soybean. This research, not previously conducted in North Dakota, will help verify use of this strategy as a productive fertilizer program.
Research outcomes:
• Study 1: Conducted four years at the NDSU Carrington Research Extension Center (REC). Treatments: Winter rye was seeded mid-September and early October at 25, 50 and 75 lb/A (six treatments). Rye was terminated with glyphosate near soybean planting time and trial data generated during soybean production. The greatest rye plant density was achieved with mid-September seeding at 75 lb/acre (4-year average = 598,300 plants/acre). Also, ground cover and foxtail suppression were greatest with the same combination. Soybean plant density and seed yield were similar among rye treatments.
• Study 2: Conducted in 2021-22 at Carrington and in 2022 at North Central (Minot) RECs. P soil analysis: Carrington=low (7 and 4 ppm) and Minot=medium (8 ppm). Treatments: 1) untreated check, 2) P fertilizer applied for corn in 2021 followed by P application in 2022 for soybean, 3) P preplant applied in 2021 for corn plus soybean. P fertilizer was applied as 0-46-0 (triple superphosphate) based on NDSU Extension recommendations for low-testing soils for corn and soybean production.
Results
o Carrington - Averaged across 2 years (on low-P testing soils, soybean yield was similar among fertilizer treatments: annual P application = 36.2 bu/A; and prior-year P application only = 37.5 bu/A.
o Minot – Soybean yield was similar among treatments.
The study continues in 2023 at Carrington.
Benefits to ND soybean farmers:
• Study 1: Greatest rye plant density was achieved with mid-September seeding at 75 lb/acre (4-year average = 598,300 plants/acre). Also, ground cover and foxtail suppression were greatest with the same combination. Soybean plant density and seed yield were similar among rye treatments. Data is now available to assist farmers with rye seeding decisions in the fall.
• Study 2: Preliminary data indicates prior-year P application provided similar soybean yield as annual application of P fertilizer. This will save fertilizer application and mechanical incorporation costs due to one vs. two applications over two years.

View uploaded report

View uploaded report 2

Winter rye cover crop establishment options, and soybean response to prior-year phosphorus application
Why the research is important to ND soybean farmers:
• Study 1: Rye fall seeding dates and rates: Determine appropriate rye seeding rate and established stand affecting soybean production including ground cover, soil moisture, and weed suppression with rye.
• Study 2: Response to prior-year application of phosphorus (P) fertilizer: Examine soybean yield response on low-P testing soil to preplant, broadcast-applied P fertilizer the prior year for corn plus soybean versus an annual application for corn followed by soybean. This research will help verify use of this strategy as a productive fertilizer program.
Research Conducted:
• Study 1: Conducted four years at the Carrington REC. Treatments: Winter rye was seeded mid-September and early October at 25, 50 and 75 lb/A (six treatments). Rye was terminated with glyphosate near soybean planting time and trial data generated during soybean production.
• Study 2: Conducted in 2021-22 at Carrington and in 2022 at North Central (Minot) RECs. P soil analysis: Carrington=low (4 ppm) and Minot=medium (8 ppm). Treatments: 1) untreated check, 2) P fertilizer applied for corn in 2021 followed by P application in 2022 for soybean, 3) P preplant applied in 2021 for corn plus soybean. P fertilizer was applied as 0-46-0 (triple superphosphate) based on NDSU Extension recommendations for low-testing soils for corn and soybean production.
Findings:
• Study 1: The greatest rye plant density was achieved with mid-September seeding at 75 lb/acre (4-year average = 598,300 plants/acre). Also, ground cover and foxtail suppression were greatest with the same combination. Soybean plant density and seed yield were similar among rye treatments.
• Study 2:
o Carrington - Averaged across two years on low-P testing soils, soybean yield was similar among fertilizer treatments: annual P application = 36.2 bu/A; and prior-year P application only = 37.5 bu/A.
o Minot – Soybean yield was similar among treatments.
Benefits/Recommendations:
• Study 1: The combination of mid-September seeding date and 50- or 75-seeding rate provided greatest cover crop ground cover and weed suppression, while maintaining favorable soybean performance.
• Study 2: Preliminary data indicates prior-year P application provided similar soybean yield as annual P use. Study continues in 2023 at the CREC.

* Study 1. Results will help farmers answer the following question: What is the best rye seeding rate based on fall seeding dates and following season factors affecting soybean production including ground cover, soil moisture, and weed suppression with rye? The information will help farmers select proper rye seeding rate and fall date based on their cover crop goals and resource management.
* Study 2. Results will help farmers answer the following question: Can P fertilizer be preplant, broadcast applied on low P-testing soil for both corn and soybean during the corn production year? If yes, this would 1) eliminate fertilizer application and incorporation costs for soybean, 2) potentially reduce P fertilizer cost for soybean, and 3) potentially increase P response by soybean.