The Horse 2020/21

Florian and I choosed the topic "soil salinization".

This topic talks about the danger that salted soil renders 2.000 hectares of land unproductive and so unusable for agriculture every day.
It is one of the reasons why we should be concerned about the future food supply. 

The management of land and water resources is responsible for the development of human-induced saline and sodic soils. The main causes are:

1. Poor drainage infrastructure which induces a rise of the groundwater table. This is a major cause of soil salinization in India, Pakistan, China, Kenya and the Central Asian countries.
2. Use of brackish groundwater for irrigation. This is a major cause of secondary salinization in parts of Asia, Europe and Africa.
3. Intrusion of seawater in coastal areas, for example in Bangladesh.
4. Poor on-farm water management and cultural practices in irrigated agriculture.
5. Continuous irrigation over very long periods, particularly in the Middle East.
6. Replacement of deep rooted perennial vegetation with shallower rooted annual crops and pastures that use less water leading to the rise of saline groundwater, for example in southern Australia.

Vocabulary

• Soil salinity: The presence of salts in the soil profile that impair crop production
• Salinization: The accumulation of soluble salts at the surface or at some point below the surface of the soil profile
• Saline soils: These are soils that contain sufficient neutral soluble salts to adversely affect the growth of most crops. The soluble salts are mainly sodium chloride (NaCl) and sodium sulphate (Na2SO4), but they may also contain appreciable quantities of chlorides and sulphates of calcium and magnesium. High salt concentrations, through their high osmotic pressure, affect plant growth by restricting water uptake by the plant roots. Salt-affected, or saline, soils include soils where the electrical conductivity of the soil exceeds 4 dS/m
• Sodic soils: Sodic soils contain sodium salts that are capable of alkaline hydrolysis, mainly sodium carbonate, Na2CO3 (in the past these soils were also called alkaline soils). Sodicity affects the soil physical characteristics like stability, water availability, permeability and toxicity to plants. Soils are classified as sodic if the exchangeable sodium percentage (ESP), which in simple terms is the total amount of 'mobile' sodium relative to the amount a particular soil can hold, exceeds 6
• Rock weathering: Significant quantities of sodium (Na), and to a lesser extent chloride (Cl), occur widely in the parent rocks from which soils form. Over time, rock weathering can lead to appreciable salt accumulation in soils if leaching is restricted. Did you know that rock weathering is the primary source of salt in seawater
• Sea water and accession of salt in marine sediments: Saline soils can form from sediments and parent materials that were once under the sea. Likewise, the salts can result from tidal inundation. Upward seepage of brackish/saline groundwater,  e.g., in the coastal areas in The Netherlands, can also result in salinization
• Atmospheric deposition: Salt derived from the sea, either deposited via rainfall or dry fallout, is the primary source of salt across large areas, e.g., many millions of hectares in southern Australia. In arid areas, salt can also be derived from dry lake beds and then be blown considerable distances by wind (e.g., Eurasia and parts of Australia)

Audio
Soil salinization.m4a (375,54 kb)

Question

Which region has the largest area of salt-affected lands?

a) North and Central Asia?

b) Africa

c) Australasia

d) Western Europe

Florian and Tiziano