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 is important 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 two ND Soybean Council research priorities: Weed #1. Weed management and #4. Soil management.
Fertilizer prices and supply, including phosphorus (P), continues to be a major crop production issue. 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 and is within the scope of ND Soybean Council research priorities: #4. Soil management – P recommendation.
Data from both studies conducted at the CREC 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. Examine winter rye fall seeding rate and date combinations:
1. Measure rye plant population and ground cover, soil moisture levels, and weed suppression prior to and/or during soybean production. 2. Measure soybean response (plant growth, and seed yield and quality) to the rye treatments.
*Study 2.
1. 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 (principle investigator); Leo Bortolon, Mike Ostlie and Kristin Simons (co-investigators)

Overview and objectives:

1. Winter rye seeding dates and rates: Research-based recommendations are needed on proper rye seeding dates and rates based on goals of North Dakota farmers for the cover crop. Objective was to identify optimum rye plant population based on combinations of fall seeding dates and rates with rye as a preplant cover crop preceding soybean considering impact on soil factors, weed control and soybean seed yield.
2. Response to prior-year application of phosphorus fertilizer: North Dakota research is needed to determine if one application of phosphorus (P) fertilizer the prior year of soybean production is effective versus annual P applications. If so, this would reduce costs of fertilizer application and incorporation for soybean. Study objective was to examine soybean 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.
Completed work:
• Trial 1: Four years of the study were completed at the Carrington Research Extension Center (REC). The trial for generating 2023 data was established continuing with the following six treatments: Winter rye was seeded on September 22 and October 14, 2022 at 25, 50 and 75 lb/A. At mid-May 2023, rye stand had low and variable density. Trial was abandoned due to inability to generate useful data.
• Trial 2: Four site years of the study were completed during 2021-23 at Carrington and North Central (Minot) RECs. P soil analysis: Carrington=2-7 ppm (very low-low) and 7.7-8 pH; and Minot=8 ppm (medium) and 6.5 pH. Treatments: 1) untreated check, 2) Preplant-applied P fertilizer applied for corn followed by P application the following year for soybean, 3) P applied for corn plus soybean during year of corn production. 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:
• Trial 1: Averaged across four years, rye plant density measured in May before soybean planting ranged from 137,800 plants/A (3 plants/ft2) with late seeding and the low seeding rate, to 598,300 plants/A (14 plants/ft2) with seeding at the early date and 75 lb/A rate. Ground cover averaged 9% with late seeding dates and low seeding rate compared to 27% with early seeding dates and greatest seeding rate. Green and yellow foxtail suppression was greatest, averaging 73% over three trials, with seeding early and at the greatest rate, when evaluated about one month after soybean planting. Soybean plant density and development, and seed yield (4-year trial average = 51.9 bu/A) and quality generally were similar among treatments.
• Trial 2:
o Carrington (three site-years) - Soybean plant development (emergence, flower and physiological maturity dates) were generally similar among treatments each year. Plant populations were similar among treatments. Seed quality (test weight, seed count, and seed oil and protein content) generally were similar among treatments. Seed yield: 1) untreated check=40.8 bu/A, 2) P application each year=44.4 bu/A, and 3) Total P application during corn year=43.8 bu/A. Yield increased with P application compared to the untreated check (LSD [0.10]=2.8 bu/A) but was similar between the P application strategies.
o Minot (one site-year) – 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 REC annual reports and websites, and ND Soybean Council 2023 annual research report.
• Presentations developed and discussed during 2023-24 winter meetings with farmers and crop advisers.
Summary:
• Trial 1: Based on this study, winter rye seeded during early fall (last-half of September) at 75 lb/A provides the greatest potential for following spring ground cover (benefits include reduction of soil erosion and excess soil moisture management) and weed suppression, while having no negative impact on soybean production when rye is properly managed.
• Trial 2: Under conditions of this study, the results indicate application of P fertilizer at NDSU recommended amounts in the preceding year of soybean production is an acceptable alternative strategy versus in-season P application for the crop.

View uploaded report

*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.