Rye use prior to soybeans has proven to be effective in many situations (erosion management, weed control, saline areas) and adopted by many producers. In past research, attempts have been made to identify safe planting conditions for soybeans into terminated or living rye. These studies have focused on termination and planting dates based on calendar dates. They have also had inconsistent results for soybean safety. Water availability is the key to soybean safety with this system. This study looks to identify a soil moisture threshold to indicate when to terminate the rye so that soybean yields are protected. Using a neutron probe, and calibrating the reading to the field site at the Carrington Research Extension Center, we will gather detailed information about soil moisture status in each of our plots. The treatments will consist of seven rye termination dates and five soil moisture check plots (bare soil x2, rye only, soybean only, and rye and soybean together). Soybean emergence, maturity, and yield data will be collected from the site. Soil moisture readings will be compared to soybean growth and yield data to determine when soil moisture drops to a level that is risky to soybeans. Information will be compared to soil moisture data collected by NDAWN to determine if that could be used as a tool to assist producers with making termination decisions.

1). Measure soil moisture status, and rye water use, with different rye termination dates

2). Estimate a soil moisture value that may result in no soybean yield loss from rye

This project has several levels of deliverables. During the course of the experiment, there will be several project updates. The most common exposure this project will receive occurs at on-site field tours. This project has already been featured at several (~3x per year) events including trainings for consultants, Extension agents, and other researchers, as well as being featured at our field days and row crop tours. The ultimate products of this project include research reports and likely a scientific publication, but more importantly it will result in a decision support tool, likely linked with NDAWN (described below). This project has already helped immensely to shift the focus of soybean producers and advisors toward soil health conversations, especially on-site where these concepts are demonstrated.

Update:
Objectives:

1). Measure soil moisture status, and rye water use, with different rye termination dates

2). Estimate a soil moisture value that may result in no soybean yield loss from rye

Completed work:

The project was carried out in 2020. Due very wet conditions in the fall of 2019 the rye was planted later than ideal. However the rye emerged in the spring of 2020 albeit at a lower stand. Yet, the rye compensated reasonably well for the thin stand and overall biomass production was not limited much by the end of the experiment. The treatments were imposed in a timely manner and the soybean growing season was favorable. The soil moisture collection went according to schedule and the data from that venture were quality. Soybean production data are yet to be processed.

Objective 1 was successfully completed, while objective 2 will be completed once the data are analyzed.

Due to the pandemic, the outreach activities for this projected were narrower in scope than intended. There was no standard field day or workshops in which visitors toured the site. However, outreach has continued through posts to social media and was featured in several regional publications this year. This winter we will be working towards our final outreach tools, with the addition of one more growing season of data.

Preliminary results:

The figure attached (below) includes some preliminary data about the rye and soybean water use in 2020. The spring conditions were very wet and, compared to previous years, the rye used very little of the available water in the soil, even during peak growing conditions. As the season turned dry, the soybean water use closely matched previous years' research values. It seems this year may be a year where it proved ok to plant ‘green’ in to living rye, based on soil moisture alone. Once the soybean yields are analyzed we will know for sure. The multi-year data are now sufficient to begin plugging in the information to start testing our hypothesis about soil moisture being the driver of success for this system.

Work to be completed:

This winter we will be developing the framework for the final multi-year analysis for this project. Over the (thus far) three year span of the project, a lot of data has been generated, but not yet combined across years. This will pave the way for a final year of data to be entered into the database and allow for a quicker turnaround for the final reporting of this project.

Otherwise, as noted, there is still data to be processed and analyzed for this current season. There are also other outreach activities this winter in which the data will be shared.

View uploaded report

The current recommendation is for rye cover crop termination at least 10 days before soybean planting.
One of the objectives of this study and other similar studies at our location was to determine whether
this recommendation should be updated.

The good news is there was no significant yield difference between plots where rye was terminated at
or before soybean planting in any of the trial years. On the other hand, in all three years there was a
large reduction in soybean yield when the rye was allowed to reach maturity within the soybean, to the
point of complete crop failure in 2018. There was substantial yield loss even in 2020, when
early-season soil moisture was abundant. Furthermore, in all three years, letting rye grow for
two weeks after soybean planting, resulted in statistically significant yield reduction. Letting the rye
grow for only 1 week also showed a decrease in yield for each of the years compared to terminating at
or before planting, but this difference was not statistically significant.

One reason that delayed termination works is that our rye water use it ultimately small compared to soybean. The reason for concern with this system is that peak rye water use has occurred around anthesis, which often coincides with the time that soybeans would normally be germinating. Timely rains during the duration of this project has meant that soybean yields were largely protected when 'planting green'. However, in prior years there have been severe yield penalties when planting green. The dataset for this trial has been instrumental in identifying water use patterns for each crop within this system, as we continue to develop the best recommendations for managing the winter rye to soybean relay system.

Rye use for a cover crop prior to soybeans is a new trend that is being adopted in North Dakota. Rye makes up for a lot of weaknesses that soybeans bring to a cropping system. Some of primary benefits include reducing soil erosion, increased weed control, additional grazing/forage material, utilization of excess soil moisture by rye allowing soybean to be planted timely, and allowing soybeans to be planted further into saline regions. The concept of this system is that winter rye is planted the fall before soybeans. The rye is terminated prior to or shortly after soybean planting. In the spring, prior to soybean planting, the rye is suppressing weeds, reducing wind and water erosion (after soybean planting too), and putting out roots and using water (in saline areas). Rye is best terminated with glyphosate.