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Agronomy QUESTION #2098
Question 1
Soil salinity is measured as electrical conductivity of saturated paste extract (\(EC_e\)) in dS/m. A soil with \(EC_e > 4\) dS/m is classified as saline because:
  • It exceeds the threshold for salt precipitation in the soil profile
  • Most sensitive crops (rice, beans, citrus) begin to show yield reduction above 4 dS/m — this threshold was established by the USDA salinity laboratory as the boundary between non-saline and saline soils affecting sensitive crop species✔️
  • All crops show complete yield loss at this salinity level
  • The osmotic pressure at 4 dS/m equals the root pressure of most crops
Correct Answer Explanation
The USDA classification: non-saline (<2 dS/m), slightly saline (2–4), moderately saline (4–8), strongly saline (8–16), very strongly saline (>16). The 4 dS/m threshold is agronomically significant because sensitive crops (beans, strawberry, rice) show measurable yield loss above this level. Tolerant crops (barley, cotton, sugar beet) withstand much higher levels — salt tolerance is crop-specific.