Soil quality

Question 1

What are soil quality indicators?

Answer 1

Physical - porosity, water content
Chemical - nutrient and heavy metal content
Biological - biodiversity

Question 2

Soil ecosystem functions?

Answer 2

Water regulation, structure and stability, biodiversity, nutrient cycling

Question 3

List at least 2 processes that lead to soil degradation?

Answer 3

Salination (presence of high salt concentrations in topsoil) and sodication (sodium saturation), sealing (anthropogenic covering of soils)

Question 4

Impacts of salination?

Answer 4

Nutrient imbalance, less biodiversity and less available water. Also lower permeability and crust formation

Question 5

Impacts of sodic soils?

Answer 5

Degradation of soil structure, less biodiversity, nutrient imbalance. Also lower permeability, cracking and dispersion of clays and organic matter

Question 6

Under what climate do you expect the highest risk of salinisation?

Answer 6

Global problem but tends to be concentrated in drylands e.g. North Africa and Australia
These locations have high evaporation rates, shallow water tables and poor natural drainage (compaction and flat terrain - little runoff)

Question 7

Would the Netherlands be susceptible to salinisation?

Answer 7

High saline content in polders during summer due to high seepage and chlorine loads. This may damage low-salt resistant crops.

Question 8

Why does a high salt content cause water stress for plants?

Answer 8

Due to reduced water uptake from osmotic imbalance (pressure gradient across membranes allowing for diffusion).

Question 9

Other effects of salinisation on plants?

Answer 9

• Reduced photosynthesis as chlorophyll is damaged
• Stunted growth from accumulation in tissues
• Salt burn
• Increased disease

Question 10

How does irrigation lead to salinisation?

Answer 10

Salt in irrigation water may remain on soil or plant surface after evaporation. Over time soil can degrade as salt builds up at surface and lower soil is waterlogged (water table rises - more salt)

Question 11

How is soil salinity measured?

Answer 11

Chemical analysis (total Siemens), TDS (mg/L), electrical conductivity (EC meter), bioindicators (halophytes - salt resistant species)

Question 12

How can saline soils be restored?

Answer 12

Reduce irrigation, improve drainage and phytoremediation