Updated January 5, 2024:
Research Overview and Objectives
There is a lack of information regarding the impact of soybean yield when cover crops are established into standing soybeans in Western North Dakota. Weed control is becoming an issue and a more integrated approach to controlling weeds is necessary to improve herbicide efficiency, while increasing profitability. Also, soil erosion is a great issue in Western North Dakota due to little residue in the soil after soybean harvest.
The objective of this research is to investigate the effects of cover crops interseeded into standing soybeans in Western North Dakota as an integrated tool to suppress weeds, increase soil cover, and improve soil health. We will measure the percentage of weed control soil cover, and soybean yield to the cover crop treatments, and we will calculate the return on the investment by using cover crops.
The studies (two separate trials) were conducted in four locations in western North Dakota (Minot, Williston, Dickinson, and Hettinger). The study considered two rows spacing, being narrow (7½ - 10”) and wide (22-30”), and each row spacing was evaluated as separate trials. The reason for investigating two rows spacing is that there is a considerable number of farmers who use air-seeders and planters to plant soybeans. Cover crops were broadcasted into standing soybeans in two stages (R2 and R5). The reason for interseed cover crops at R2 stage is to provide more time for the cover crops to get established, and we can increase the chance of getting more moisture in the field for seed germination. The reason for interseed cover crops at the R5 stage is because it is close to the senescence and we can reduce the cover crop competition with soybeans, even though soil moisture at this stage is typically low for seed germination. We investigated five cover crop treatments: no cover crops; winter rye; winter rye + winter canola; winter rye + winter camelina; and winter rye + oats + radish. Cover crop seeding rates were at the recommended rates for cover crop establishment, and the seeds were surface broadcast applied at the two soybean stages.
All trials were conducted using best management practices for Western North Dakota soybean production, and all trials were under no-till. The experimental design was a randomized complete block with four replications.
Evaluations on soybeans were plant population at harvest; yield; test weight; oil, and protein. For cover crops, we evaluated: soil cover (using the software Canopeo) and biomass 30 days after harvest.
For weeds, we evaluated weed presence/suppression in the fall.
Completed Work: Deliverables and/or Milestones.
The trials were planted according to Table 1. All the trials were planted as planned. The evaluations cited in Table 1 such as soybean harvest, soil cover evaluation with Canopeo, cover crop biomass evaluation, and weed count were all done for all sites. We also have finalized the soybean oil and protein content and soybean test weight.
Table 1. Soybean Planting date, R2 and R5 stage, and harvest dates. Soil cover, cover crop biomass, and weed count dates.
Operation Minot Dickinson Williston§ Nesson Valley§ Hettinger
Planting June 2 May 19 June 6 May 29 May 18
R2 stage July 26 July 5 Aug 3 Aug 3 July 11
R5 stage Sep 15 Aug 22 - - Aug 22
Harvest Oct 16 Oct 25 - - Oct 6
Soil Cover Nov 17 Nov 21 - - Nov 21
CC Biomass Nov 17 Nov 21 - - Nov 21
Weeds count Nov 17 Nov 21 - - Nov 21
§ Dates missing for Williston and Nesson Valley due to the trial lost by hail
Progress of Work and Results to Date
The trials were well established in all locations across Western North Dakota. The excessive moisture during the spring imposed a challenge to plant the trials early in the season. On August 3 a severe hailstorm happened in northwestern North Dakota and the trials in Williston and Nesson Valley were lost. Cover crops were not established in Dickinson and Hettinger. The reason for the no establishment was related to the lack of moisture for the cover crop germination and establishment. In Minot, given the late planting date, the cover crops got more moisture after planting. However, most winter rye was properly established in both R2 and R5 stages. Percentage of soil cover and cover crop biomass data were collected in all trials. Weed counts were performed in all trials as well as planned in the project. The most common weed found was voluntary grains in very low incidence.
The results are still being processed for further analysis and they cannot be completed to present in this report.
Work to be Completed.
Data analysis for all variables in the trials must be completed in the months to come. Amino acids evaluation on soybean seeds will be analyzed in the weeks to come since we need to find a laboratory to run those analyses. In the spring (before burndown for the next crop) cover crop stand will be evaluated again. For weeds, we will evaluate weed presence/suppression in the spring before the burndown for the next crop, and the percentage of suppression will be calculated. In all trials we will calculate the return on the investment (ROI): we are going to calculate the ROI based on the equation: ROI = gross income (yield × commodity price) - treatment cost.
Other relevant information: potential barriers to achieving objectives, risk mitigation strategies, or breakthroughs.
We found that for Western North Dakota using the soybean stage only to define the time to seed the cover crops will impose risk for the cover crop establishment. In the second year of the study, we will couple the stage and moisture available to improve the chance of cover crop establishment.
View uploaded report 2 