Subtopic: I.C. engine systems – fuel, cooling, lubrication, ignition, electrical, intake and exhaust
Question Statement:
The USDA classification of irrigation water with regard to alkali and salinity hazards is based on
Options:
(A) Exchangeable sodium percentage and pH
(B) Electrical conductivity and Sodium adsorption ratio
(C) Electrical conductivity and pH
(D) Sodium percentage and pH
Official Answer Key:
B
Step-by-Step Solution & Explanation
The USDA Salinity Laboratory diagram classifies irrigation water quality on a two-axis basis: Electrical Conductivity (EC), which indicates the total salinity hazard, plotted against the Sodium Adsorption Ratio (SAR), which indicates the sodium (alkali) hazard. This EC–SAR classification is the standard USDA method. The other options substitute pH or exchangeable sodium percentage, which are used in related but distinct classification schemes (e.g. Wilcox diagram elements, ESP-based sodicity assessment), not the primary USDA EC-SAR classification. Hence (B) is correct.
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