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 soil moisture thresholds that increase risk of soybean yield loss

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 (if possible next year). This project has generally 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, regardless of their intentions for specifically using rye as a relay crop.

Updated November 29, 2021:
See attached file

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Rye use for a cover crop prior to soybeans has become a trend being adopted in North Dakota. Rye makes up for a lot of weaknesses that soybeans bring to a cropping system. Some of the 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.
Rye provides selective weed suppression, meaning that it is more effective against some species than others. Rye is particularly effective at suppressing kochia (up to 70% control in a heavy kochia infestation at CREC), and also does well against pigweed species, ragweed, and yellow foxtail. Rye has very little or no suppression of mint species (like lanceleaf sage), or most legumes. Thus, soybeans are not influenced by the presence of rye, except when moisture is limiting. In 2016 and 2017, when the springs have been very dry in Carrington, we’ve seen heavy injury to soybeans as a result of the limited rain. From 2013-2015 our results have shown rye to be very safe to soybeans, when there was more available moisture. This past research has led us to the finale of this current project which would seek to identify when soil moisture drops to a level that creates risk to soybeans from the rye. The research leaders involved with this project have had past experience and training in monitoring soil water use and moisture status with other projects.
Many producers are beginning to see the advantages of using rye prior to soybeans. However as mentioned, this system comes with risks. As more people adopt this system there are more opportunities for things to go wrong (particularly as people get familiar with managing a new system). By accomplishing the stated goals of this study, we would provide the information needed to minimize risk to soybean producers. In 2016, the moisture deficit was so severe in Carrington that the only time rye was safe with soybeans was when it was terminated early in the spring. I haven’t been made aware of any crop failures from rye as of yet, but the potential is there. The key to avoiding that scenario is to manage the risk factors.