Understanding Solonetz Soil and its Terms

Solonetz soil is a specific type of soil that is strongly affected by sodium. These soils are characterized by a high percentage of exchangeable sodium, particularly in the subsoil horizon (often denoted as the Bt horizon or natric horizon).

The presence of high exchangeable sodium leads to several issues:

• It causes clay particles to disperse.
• It often results in poor soil structure, which reduces water infiltration and drainage.
• It typically leads to a high pH (alkaline) condition.

Because of the high alkalinity and dispersed organic matter (due to the high sodium), the soil surface can appear dark or black, and it feels sticky when wet. This characteristic dark appearance and high pH are why Solonetz soil is commonly termed as Black alkali soil.

Let's look at why other options might not be appropriate:

• Non-saline soil: Solonetz soil is not necessarily non-saline; it can also contain salts. However, its defining characteristic is high exchangeable sodium leading to alkalinity and structural problems, distinct from soils primarily affected only by soluble salts.
• Highly saline soil: Highly saline soils, often called Solonchaks, are primarily affected by high concentrations of soluble salts. While Solonetz soils can also have salts, their main issue is the high exchangeable sodium and resulting high pH and poor structure, which differentiates them from purely saline soils. Saline soils typically have a neutral to slightly acidic or slightly alkaline pH, usually below pH 8.5.
• White alkali soil: This term usually refers to saline soils (Solonchaks) where visible white salt crusts appear on the surface due to evaporation. While some Solonetz soils might have some surface salts, the term "white alkali" specifically points to the visible salt accumulation of saline soils, not the characteristic dark color and structural issues of Solonetz caused by high exchangeable sodium and pH.

Therefore, the most appropriate alternative term for Solonetz soil, highlighting its key characteristics of high alkalinity and often dark appearance due to dispersed organic matter, is Black alkali soil.