Since the growing season of 2017, we have been monitoring soil properties, crop growth, and insect communities in four fields affected by salinity. Across each field, we have maintained strips of a cereal rye cover crop, established for the purposes of assessing its ability to improve soil health and reduce effects of salinity on soybeans. The 2021 FY is our final year of the project. All field operations have been completed and nearly all data has been collected. At this time, we are working on data analysis and communication of the study.

Objective 1: We will measure the benefits and risks of using a cereal rye cover crop in a soybean-corn rotation to determine its potential for salinity management and building soil health. We will use a whole-system approach to measure soil, crop, weed, and insect responses to the salts and the cover crop. These field-scale experiments will compare cover crop and no cover crop treatments across a gradient of saline soils, replicated across four farms, and spanning two rotation cycles to capture variability in responses across different soil types and climates. Interactions between soybeans and cereal rye (specifically water use and soil health) will be further investigated in the greenhouse.

Objective 2: We will directly provide information to ND soybean farmers about the challenges of farming on saline soils, the use of cereal rye in managing salinity, potential benefits and risks of using cereal rye, and guidance in where, when, and how to effectively use cereal rye as a salinity management tool. We will deliver this information to farmers through the NDSU Soil Health extension program, with videos, fact sheets, field days, and online media. We will also incorporate salinity education and management information into café talk programs.

• A better understanding of the nature of saline soils in eastern North Dakota, specifically: A complete and thorough survey of soil organisms (from bacteria to soil-dwelling insects) occupying saline and non-saline soils, and in the presence and absence of a cereal rye cover crop.
• A better understanding of cereal rye as a management tool for saline soils, and particularly in terms of cereal rye tolerance, water use, and general performance across a gradient of saline soils.
• Academic publications, presentations, and education and outreach materials that summarize the project and our findings.

Update:
Objectives of the research
Objective 1: We will measure the benefits and risks of using a cereal rye cover crop in a soybean-corn rotation to determine its potential for salinity management and building soil health. We will use a whole-system approach to measure soil, crop, weed, and insect responses to the salts and the cover crop. These field-scale experiments will compare cover crop and no cover crop treatments across a gradient of saline soils, replicated across four farms, and spanning two rotation cycles to capture variability in responses across different soil types and climates. Interactions between soybeans and cereal rye (specifically water use and soil health) will be further investigated in the greenhouse.

Objective 2: We will directly provide information to ND soybean farmers about the challenges of farming on saline soils, the use of cereal rye in managing salinity, potential benefits and risks of using cereal rye, and guidance in where, when, and how to effectively use cereal rye as a salinity management tool. We will deliver this information to farmers through the NDSU Soil Health extension program, with videos, fact sheets, field days, and online media. We will also incorporate salinity education and management information into café talk programs.

Completed work
This grant has supported a multi-year project (FY18 through FY21), this list reflects all the completed activities to date.
• Formed cooperative agreements with four farmers, on four working farms that hosted saline patches. These field sites are located in Aneta, Northwood, and Jamestown, North Dakota.
• In the spring of 2017 and prior to planting, we Veris mapped and ground-truthed each field to locate four replicated sets of plots that span saline and non-saline areas. We also installed weather stations at each of the four sites. The weather stations collect frequent readings of air temperature, precipitation, wind direction and speed, relative humidity, and solar intensity.
• In 2017 and 2019, the Aneta and Northwood sites were planted to corn and the two Jamestown sites were planted to soybean. In 2018, the other phases of the respective rotations were planted in each field. In 2020, three of the fields were prevent plant; the Aneta field was planted to soybean.
• Mid-season in each year, we interseeded treatment strips of cereal rye into growing cash crops and immediately began monitoring soil water content every other week. In 2017 and 2018, we applied the cereal rye at 40 lb/ac; in 2019 and 2020, we increased the rate of cereal rye to 80 lb/ac.
• Mid-season in each year, we sampled soil microbial communities, to examine baseline differences between soil communities in saline and non-saline soils and in response to cereal rye treatments.
• Mid-season in 2017 and 2018, we surveyed arthropod communities, to examine baseline differences between soil communities in saline and non-saline soils and in response to cereal rye treatments. In 2018, we surveyed fields for potential invertebrate pests (cutworm).
• In 2019, we sampled soils for nematode community analysis, to examine baseline differences between soil communities in saline and non-saline soils and in response to cereal rye treatments.
• End-of-season in each year, we collected plant biomass for cash crop yield, cover crop biomass, and weed biomass.
• End-of-season in each year, we sampled soil for fertility and soil health measurements. This supplements extensive soil descriptions that we conducted in 2017 for each field at the start of the project and again in 2020 at the end of the project.
• Each year, cereal rye is terminated two weeks before corn, or immediately after planting soybean.
• We conducted a greenhouse study to assess cereal rye tolerance to increasing salinity rates, cereal rye water use, and soybean performance after soil had been “conditioned” with cereal rye.
• We have applied a salinity-yield calculator tool into a spatial analysis of our four subject fields, to evaluate how returns are affected by salinity for corn, soybean, and wheat. This work will create demonstration scenarios to communicate impacts of salinity on crop yields and farm economics.
• The Jamestown fields were highlighted in the Soil Health Bus tour, July 25-26, 2018.
• PI Gasch has presented work on saline soils and soil health at the annual Agronomy-Crops-Soils meetings in Tampa, FL in Oct. 2017, Baltimore, MD in Nov. 2018, and San Antonio, TX in Nov. 2019, at the Manitoba Soil Science Society and CropConnect meetings in Winnipeg, MB in Feb. 2018, and at the Soil Ecology Society Biennial meeting in Toledo, OH, along with graduate student Mackenzie Ries.
• Graduate student Mackenzie Ries, funded by this grant, completed her MS degree in May of 2020.

Preliminary results
• Saline soils tend to hold more water throughout the growing season. The cereal rye, at a 40 lb/ac rate has not appeared to rob the cash crop of water and has not appeared to drastically change soil water content in saline areas. Thus, we increased the rate to 80 lb/ac for the second round of the rotation at these locations.
• Saline soils also tend to hold more fertility. This may be because fertilizer is still applied to the un-productive areas, and/or because nutrients move with soil water, which accumulates in the low-lying (saline) parts of the fields.
• Soil structure is generally better in non-saline parts of the field, allowing better drainage and rooting conditions. We hope that the cereal rye improves soil structure in the saline areas.
• As a result of these water and nutrient conditions in saline soils, microbial biomass is actually higher in the saline soils. We do not know yet if this is good or bad, but it has been a surprising result. We have also learned that earthworms are avoiding saline areas, but that surface residue encourages them to colonize saline areas.
• We are still analyzing data on arthropod communities, and it appears that some groups of springtails (small detritivores) respond to salinity differently, depending on which crop is growing in the field. We also did not find any pest species in these surveys that were of concern, including the cutworms.
• During the 2018 Soil Health bus tour, farmers expressed strong interest in using cereal rye and other small grains in managing salinity. Based upon questions that we received at this event, it is clear that education about salinity and its management is in demand.
• After final soil and cover crop samples were collected in the summer and fall of 2020, our weather stations were removed and the field operations have been completed.


Work to be completed
• Compile soil biological and insect community surveys (from 2017 – 2020) and identify specific groups of concern (beneficials and pests) in saline and non-saline areas, and in association with cereal rye. New in 2020, PI Banerjee will be assisting in providing molecular analysis of soil microbial communities. This information will greatly supplement the dataset generated from this project.
• Graduate student Alec Deschene, partially funded by this project, is currently writing his thesis and aiming to graduate in the spring of 2021.
• Provide education on saline soil nature and management in winter extension programs (workshops and café talks).
• Produce peer-reviewed literature on the many aspects of this project.

Update:

View uploaded report

Managing salinity with cover crops: a whole system response (year 4)
Caley Gasch, Jason Harmon, Sam Banerjee, Tom DeSutter, Abbey Wick

Research conducted
In the 2019 growing season, we interseeded cereal rye (80 lb/ac) into strips in soybean fields and monitored soil water content (0-6”) in the rye strips and adjacent control strips that traversed saline and non-saline portions of the fields. We also grew cereal rye at different seeding rates (40, 80, 120, and 240 lb/ac) in replicated pots in the greenhouse with an unlimited water supply for five weeks.

Why the research is important to ND soybean producers
Soil salinity management is only possible through managing water. Soil water removal by plants (transpiration) is an effective way to dry the soil, while encouraging salts to remain deep in the soil profile. We wanted to quantify cereal rye water use so that we can better understand the potential of this cover crop species to assist in salt and water management and make appropriate seeding rate recommendations.

Benefits/recommendations to ND soybean farmers and industry
Soil water content in the field was consistent throughout the 2019 season and did not differ between cereal rye and control strips. Soil water was a little higher in saline soils, which produced less cereal rye biomass than non-saline soils (see Figure 1). Cereal rye grows well in soils up to salinity levels of 6 dS/m (saturated paste extract). In the greenhouse, cereal rye biomass production and cumulative transpiration increased as seeding rate increased to 120 lb/ac (see Figure 2). We did not measure spring water use but fall cereal rye transpiration is similar to that of winter small grains (25 inches of water per year).

If water use is the goal of growing cereal rye, we recommend using the highest seeding rate within your comfort level. We found that a seeding rate (drilled) between 120 – 240 lb/ac would provide the most water use.

Soil salinity affects approximately 13% of the land area in North Dakota and saline patches reduce yield and profit. Researchers and farmers will benefit from a better understanding of the nature and limitations of saline soils, as well as effective strategies to manage salts. Furthermore, cover crop use and interest is on the rise in North Dakota, yet we have a lot to learn about risks and benefits associated with using cover crops in soybean.