What Salinity Will Stunt the Germination of a Bean Plant?

Soil Salts

• Soil salts can be composed of calcium, magnesium and potassium as well as sodium chlorides, sulfates, carbonates and nitrates. Saline soils contain a measurable amount of one or more of these water-soluble salts. High amounts of exchangeable sodium characterize soils labeled sodic. High-salt soils can be saline, sodic or both. Salts can occur naturally; Colorado mountain soils and sandy soils in Arizona and California have high salt contents. Salts can be impacted by human interaction with land. A byproduct of Montana coal-mining is an increase in the salt content of water.

How Soil Salts Affect Plant Growth

• In salt-sensitive plants like beans, soil salts badly impact on cellular water content. Plants can no longer absorb and process nutrients needed for all phases of growth. Mild salt sensitivity may be visible as withering or burning on leaf edges. More extreme symptoms drastically reduce crop levels.

Soil Salt Content Measurement

• Soil salinity is measured by testing the electrical conductivity of saturated test samples. Electric conductivity, EC, is measured in deciSiemens per meter, dS/m. High dS/m levels are associated with high salinity levels and low dS/m with low salinity and less effect on plant growth.

Salinity and Beans

• Quick-growing, water-guzzling bean crops display strong sensitivity to soil salts. Measured in EC units, an increase in saline level from 1.0 to 3.3 can reduce bean crop yield by half. At an EC level of 6.0, few beans survive; at a level of 7.0, beans fail to grow. While these studies do not specify bean type, a California study of commercial snap bean production asserts that a level of 3.6 reduces snap bean crops by 50 percent.

Remediation

• The most effective remediation for high soil-salt levels is dilution with water. Shallow-rooted, beans present a problem for attempts to reduce saline or sodic levels with irrigation. Too much water or water that stands in fields can drown bean plants. The best remediation for bean sensitivity to soil salts remains to plant beans only where levels are low.