The soil becomes partially infertile when its pH value is about

Explanation:

When the soil has pH value greater than 11, it is termed as practically infertile.

Causes of high soil pH:

• Sources of alkalinity.
• Role of cations (Na and Ca)
• Influence of soluble salt levels
• Influence of carbon dioxide and carbonates.

Important Points

1. If the pH in the case of saline soil is around 8.5, very good structure
2. And in the case of saline-sodic soil, it is from 8.5 to 10, good structure.
3. And in the case of sodic soil, it is generally greater than 10, structureless.

Note:

Why high pH soils are infertile:

The high pH caused due to the presence of sodium carbonate which is highly soluble.

This high pH causes fulvic and humic acid of organic matter to get dissolve and when the water evaporates, it gives the surface a black color.

This sodic soil creates physical disintegration and due to high sodium and low salt concentration, slaking, swelling and dispersion occurs which caused coagulation of soil particles as Vander Vaal forces dominate due to deficiency of hydrated ions. 

Complete dispersion causes soil crusting and as a result of this germination problem due to clogs that restrict soil and air movement and makes soil infertile.