Soil salinity is a significant agricultural problem in North Dakota, with more than 1.9 million acres affected across the state, challenging crop production differently. Soils with a high content of soluble salts often exhibit a white crust on the surface, and the most common components are sulfate salts, carbonates, and chlorides. A soil is considered saline when the electrical conductivity (EC) exceeds 4 mmhos/cm (Franzen et al., 2019; Seelig, 2000).
Soybean is a legume crop that is sensitive to salinity. In sandy loam soils in ND with EC over 1.1 mmhos/cm it is possible to see 20-25% yield reduction, reaching 50% yield loss over 2 mmhos/cm (Butcher et al., 2015).
Salinity mitigation is a water management issue in ND. Decreasing evaporation and increasing soil drainage are essential tools to mitigate adverse effects. The use of cover crops has many benefits in cropping systems, such as reducing soil erosion, soil compaction, NO3-N leaching, increased soil organic matter and carbon, and introducing new N through biological N2 fixation if legumes are used as a cover crop. Additionally, cover crops may help suppress weeds and certain diseases (Colazo and Buschiazzo, 2010; Blanco-Canqui et al., 2015; Marinari et al., 2015). Cover crops can be used as a green cover to decrease soil surface evaporation, and improve drainage through root channels.
Winter cover crops need vernalization for bolting, and because of that, winter rye, winter camelina, radish, and kernza will be kept in the vegetative stage, acting as green mulch in between the soybean rows, decreasing surface evaporation and adding root channels that will increase drainage. Also, adding a cover crop in the system will increase diversity and improve microbial communities, leading to salt mitigation effects in soybeans. In North Dakota, winter rye was used to mitigate the unfavorable effect of saline conditions in soybeans. A significant increase of beneficial soil microbes was reported that could alleviate the adverse effects of salinity (Dasgupta et al., 2023)
Adding cover crops in the same growing season will allow soybeans to grow in a less inhospitable environment when they face saline conditions, increasing grain yield.

Hypothesis: Winter cover crops, will act as green mulch during the growing season, alleviating salinity problems, obtaining significantly soybean higher yields
Objectives:
• To determine the cover crop seeding rate to improve soybean yield in saline conditions
• To determine termination cover crop date, to get the highest soybean yield in saline soil conditions.

Methodology to attain objectives
Experimental design: The experiment will be conducted in Carrington for two years for soybean-cover crops. The trial will be established under dryland. The experimental design will be a randomized complete block design (RCBD) with a factorial arrangement with four replicates (Table 1). The first factor will be five cover crop treatments: soybean (check), soybean and winter rye, winter barley, winter camelina, and a cover crop mix. The second factor will include cover crops, with 66% and 33% of the recommended rate, respectively. The third factor will be the cover crop termination date, the first will be cover crop termination with glyphosate at R2 soybean stage, and the second without termination: The experimental unit will be 10 ft x 25ft.
Table 1. Treatment structure

Salinity mapping: A salinity map will be made in the trail area, using EM38, and apparent electrical conductivity (ECa) will be recorded and mapped in ArcGIS, with the idea of identifying the salinity gradient in the soil, facilitating the field design and analysis.

Soil sampling: Composite samples will be taken at 0-6 and 6-24 inch depth in early spring, with the the top soil to be analyzed for NO3-N, pH, P, K, Sulfate-S, Zinc, pH, EC, and organic matter, and samples taken at 6-24 inches will be tested for NO3-N and Sulfate-S. The results will be used to determine the P, K, and S fertilizer application. In-season soil sampling for electrical conductivity and pH will be done at the R2 soybean stage at the 0-6 inch depth.

Plant Sampling: Mid-season biomass samples will be taken from a 1 m section of an internal row at the R2 soybean growth stage. These samples will be dried and weighed to determine biomass production. At the same time, an above-ground biomass sample of the cover crop will also be taken. Shortly before soybean harvest, cover crop biomass samples will be taken in all plots where glyphosate was not sprayed. At soybean harvest, grain yield, test weight, grain protein, and grain oil data will be collected.

Weather and soil data: Daily temperature (min and max), relative humidity, and rainfall will be obtained from NDAWN stations. Soil moisture and temperature will be obtained from 1 rep of the experiment with a Decagon 5TM soil moisture sensor (5 cm depth), and reads will be recorded daily with a Decagon EM50 datalogger.

Canopy multispectral data: A Crop Circle ACS-430 (Holland Scientific Inc, Lincon, NE, USA) optical active sensor will collect canopy reflectance at 670, 730, and 780 nm (red, red-edge, and near-infrared light) in each plot.

A drone DJI Phantom with a Micasense Red-Edge multispectral camera will collect canopy reflectance data at 550, 670, 715, and 840 nm (green, red, red-edge, and near-infrared light) at V3, R2, R6, and R8 soybean stages. Once images are obtained, several vegetation spectral indices (VIs) will be calculated using MATLAB 2023b.

ECa and soil water content: Electromagnetic Induction (EM38) readings (ECa) will be calibrated for EC and soil volumetric water content in the trial area. Each plot will be measured at 0-6 and 6-24 inches in 15-day intervals during the growing season when soil moisture is not under saturation conditions (for example, after rain).

Statistical analysis will be based on an RCBD design with a factorial arrangement. All variables mentioned above will be tested with analysis of variance using the MIXED procedure of SAS 9.4, and the means separation LSD test (P = 0.05).

• Winter cover crops will alleviate salinity problems, obtaining significantly higher soybean yields.
• It will allow the incorporation of soybean in the crop rotation, in soils where it was already challenging to produce it profitable, because of salinity problems
• This study will allow us to determine the cover crop seeding rate and termination date, as a starting point, to achieve higher soybean yield in saline soils

The main output of the research will be a significant increase in soybean yield under saline conditions. It will allow farmers to get a profitable crop in places where it was not economically advantageous to plant soybeans, resulting in more diversity and better revenue.