Update:
We have successfully completed three years of data collection on soybean fields that have reduced productivity due to soil salinity. We will complete final sampling and site analysis in 2020. In 2019, we focused on characterizing the soil microbial community associated with saline soils, and we conducted an economic analysis of salinity-related losses in soybean production. The technical report (attached) details this work.

View uploaded report

Research conducted
For three years, we have been monitoring soil properties and plant growth in four fields that have reduced crop production due to saline soils. We’ve been collecting field data on soils, soybeans, corn, and cover crops, but we’ve also been working on an economic analysis of the salty areas and thinking about ways to improve net profitability and productivity on these fields.

We used Dr. David Ripplinger’s salinity-yield calculator (https://www.ag.ndsu.edu/bioeconomics/Library/tools/salinity-economics-tool/view) to estimate cash returns across fields, based on a salinity map of our study sites. The tool considers fixed costs and has adjustable inputs for fertilizer costs (if applicable), baseline yields for non-saline soils, and grain prices. We then map the returns to identify nonprofitable portions of the field, and to estimate total field-level returns.

Why the research is important to ND soybean farmers
Salinity is a common problem across North Dakota, and soybean plants are especially sensitive to salts. Since salinity severity can vary from year-to-year, farmers may be willing to take a gamble and plant soybeans in salty areas; however, the combination of yield reductions and the costs of farming unproductive areas can drastically reduce field-level profit.

Final findings of the research
In our example field in Figure 1, 40 acres (50%) of the field was not profitable due to salinity-caused yield reductions in soybean. The total estimated return for the 80-acre field was $1,895. We estimated that 20-38% of our other three study sites were not profitable for soybeans. Since the salinity occurs in fairly large, connected patches, the field in the example would be a good candidate for separating nonprofitable areas into a different management zone. Soybeans are still a good crop choice for non-saline portions of the field.

Benefits/recommendations to North Dakota soybean farmers and industry
In fields that have consistent yield reductions due to salinity, we suggest identifying areas of the field that could be removed from soybean production. Those zones could be planted to a more salt-tolerant crop, cover crop, or forage mix. This approach improves farm enterprise profits and it addresses the salinity problem by encouraging water use and active plant growth in areas that cannot support soybeans—a win-win for the farmer and soil health!