Understanding Acidic Soil: Causes and Effects

6 Questions

What role do microorganisms play in causing acidic soil?

Breaking down organic matter and releasing carbon dioxide

How do plants contribute to the acidity of the soil?

By releasing H+ ions to maintain a neutral charge in their roots

Which human activity is a major contributor to the acidity of rain, impacting soil pH levels?

Burning fossil fuels releasing oxides of sulfur and nitrogen

How does the use of ammonium fertilizers impact soil acidity?

Reacts in the soil, forming nitrate and releasing H+ ions

What is one way plants help solubilize metal nutrients, potentially increasing soil acidity?

By exuding organic acids

Which natural process contributes to increasing acidity in the soil due to the release of carbon dioxide?

Root respiration and organic matter decomposition

Study Notes

Understanding Acidic Soil: Causes and Effects

Acidic soil, with a pH level below 7 (neutral), can negatively impact plant growth and soil health. There are several causes of acidic soil, including natural processes such as root respiration and decomposition of organic matter by microorganisms, as well as human activities like mining and the use of certain fertilizers.

Natural Processes

Root Respiration and Organic Matter Decomposition: Microorganisms break down organic matter in the soil, releasing carbon dioxide (CO2) which can increase acidity.
Plant Growth: Plants take up nutrients in the form of ions (e.g., NO3-, NH4+, Ca2+, H2PO4-) and often take up more cations than anions. To maintain a neutral charge in their roots, plants release H+ ions, which can lower soil pH. Some plants also exude organic acids to help solubilize metal nutrients like iron (Fe).
Fertilizer Use: Ammonium (NH4+) fertilizers react in the soil through nitrification, forming nitrate (NO3-), and in the process release H+ ions.

Human Activities

Acid Rain: Burning fossil fuels releases oxides of sulfur and nitrogen into the atmosphere, which can react with water to form sulfuric and nitric acid in rain.
Oxidative Weathering: Oxidation of primary minerals, especially those containing Fe2+, generates acidity. This process can be accelerated by human activity, such as mine spoil, which can form severely acidic conditions in soils near some mine spoils due to the oxidation of pyrite.

Acidic soil can lead to poor plant growth, reduced nutrient availability, and decreased soil structure. To counteract acidic soil, various methods can be used, such as adding base materials to increase soil pH.