The Effects of Soil Solution Electrical Conductivity and Sodium Adsorption Ratio on Soil Liquid Limit and Soil Strength

Abstract

ABSTRACT Irrigation water quality is a global agricultural management issue. High solution sodium adsorption ratio (SAR) and low electrical conductivity (EC) of irrigation waters decrease both hydraulic conductivity and aggregate stability. Little is known how solution EC and SAR affects soil mechanical properties. Three smectitic soils were treated with salt solutions made from sodium and calcium chloride that had SAR levels of 5 and 17 at solution levels between 5 and 40 millimoles charge per liter (mmolc L−1). Soil Atterberg limits were measured using Cassagrande method and penetration resistance was measured using a falling cone penetrometer. At 5 mmolc L −1, whole soil liquid limits increased from 46% to 50% on average when solution SAR levels increased from 5 to 17, whereas plastic limit did not change. When comparing the effect of increasing SAR from 5 to 17 at a salinity level of 5 mmolc L−1 on the Aberdeen soil, the water content increased at soil strengths between 0.5 and 100 kPa. Increasing soil solution SAR at low EC levels alters soil mechanical properties leading to undesirable soil qualities for agricultural production, specifically creating greater difficulty for seedling emergence and increasing the force required for tillage.