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.
In Carrington 2024, salinity severely affected soybeans when EC (1:1) was above 1.8, decreasing more than 50% compared to EC levels of 0.63. One of the main findings was that winter barley, planted in spring, increased soybean yield significantly by 7% compared with the check plot, indicating the benefit of salinity mitigation using cover crops in saline areas. However, it is essential to note that these benefits were achieved with a low cover crop seeding rate and a termination time of soybean R2. Cover crops offer multiple benefits and will be studied in further research. I am attaching Figure 1 with preliminary data at the end of the document.
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.