Difference Between Saline and Alkaline Soils

The key difference between saline and alkaline soils is that saline soils have a pH less than 8.5 and an exchangeable sodium percentage less than 15, while alkaline soils have a pH greater than 8.5 and an exchangeable sodium percentage higher than 15.

Soil pH is an important parameter in terms of soil fertility. It affects the availability of nutrients for plants. Moreover, soil pH affects the activity of soil microorganisms. Based on the soil pH, there are several categories of soil. Acidic soil and basic soil are two major types among them. Acidic soils have pH less than 7 while basic soils have pH greater than 7. Meanwhile, neutral soils have pH 7.  Alkaline soils and saline soils are two types of basic soils. Saline soil has pH in between 7 to 8.5 while alkaline soils have pH greater than 8.5.

CONTENTS

1. Overview and Key Difference
2. What are Saline Soils
3. What are Alkaline Soils
4. Similarities Between Saline and Alkaline Soils
5. Side by Side Comparison – Saline vs Alkaline Soils in Tabular Form
6. Summary

What are Saline Soils?

Saline soil contains high contents of soluble salts. Sodium salts are predominant in the saline soil. In addition, K+, Ca2+, Mg2+ and Cl− are also responsible for the salinity of the soil. Hence, it has a basic pH range; 7 – 8.5. In saline soil, exchangeable sodium percentage is less than 15%. But, its electrical conductivity is 4 or more mmhos/cm. The salinity of the soil increases due to various reasons such as mineral weathering, excessive irrigation and the use of fertilizers and animal wastes, etc.

Soil salinity does not favour plant growth. Thus, it negatively affects crop yield. Furthermore, salinity also causes necrosis of leaf margins, stunted plants, wilting and plant death under severe conditions. Reclaiming the soil by leaching with good quality water is a method to reduce the soil salinity. However, this can pollute the groundwater and surface water. Another solution in agriculture for saline soil is the growing of salt tolerant crops.

What are Alkaline Soils?

Alkaline soils are clay soils that have a pH greater than 8.5. The high pH is due to the high levels of sodium, calcium, and magnesium. Moreover, hard water can also raise the pH of the soil to alkaline levels. However, the dominating compound in alkaline soil is sodium carbonate. Sodium carbonate causes alkaline soils to swell.

Besides, alkaline soils have an exchangeable sodium percentage greater than 15% and electrical conductivity less than 4 mmhos/cm. Also, similar to saline soils, the availability of plant nutrients in alkaline soil is low. Nevertheless, some plants such as lilies, geraniums and maidenhair fern thrive in this soil. Some examples of high alkaline soils are dense forests, peat bogs and soil with a high quantity of certain minerals.

What are the Similarities Between Saline and Alkaline Soils?

• Both saline and alkaline soils have a pH greater than 7.
• In both soils, the availability of plants nutrients is low.
• Also, both soils do not favour plant growth.
• Besides, these soils occur in areas having little rainfall.
• Moreover, mineral weathering too causes the development of both these soils.

What is the Difference Between Saline and Alkaline Soils?

The key difference between saline and alkaline soils is that pH of the saline soils ranges in between 7 to 8.5 while the pH of the alkaline soils is greater than 8.5. Furthermore, saline soils have an exchangeable sodium percentage of less than 15% while alkaline soils have an exchangeable sodium percentage greater than 15%. So, this is also a difference between saline and alkaline soils.

Moreover, the electrical conductivity of saline soil is high while it is low in alkaline soils. Also, the organic matter content in saline soils is comparatively higher than alkaline soils.

The below infographic summarizes the difference between saline and alkaline soils comparatively.

Summary – Saline vs Alkaline Soils

Saline soils and alkaline soils are two types of soils that have basic properties. In summary of the difference between saline and alkaline soils, saline soils have pH less than 8.5 and exchangeable sodium percentage less than 15, while alkaline soils have pH greater than 8.5 and exchangeable sodium percentage higher than 15. However, both soils do not favour proper plant growth due to low availability of plant nutrients.

Reference:

1. Soil.”, “Saline. “Saline Soil.” Environmental Encyclopedia, Encyclopedia.com, 2019, Available here.
2. “Alkali Soil.” Wikipedia, Wikimedia Foundation, 8 June 2019, Available here.

Image Courtesy:

1. “Salinity” By USDA Employee –  (Public Domain) via Commons Wikimedia
2. “Rice Field” By Unknown – USAID Bangladesh (Public Domain) via Commons Wikimedia