Soil Chemistry

Question 0

Bulk density -

Answer 0

The mass of a specific volume of dry soil (including pore space and solids)

Question 1

Particle density -

Answer 1

The mass per volume of the different particles in soil.

Question 2

Water logging results in: (6)

Answer 2

Poorly aerated soils, low O2 levels. 
CO2 present as methane gas. 
Lower decomp levels. 
Restriction of aerobic plant growth. 
Reduced microbial activity. 
Oxidised nitrogen, NO3^-, may be released as N2 and N2O into the atmosphere.

Question 3

Soil solution contains: (4)

Answer 3

Ions from atmospheric deposition.
CO2 from root respiration.
Dissolved nutrient ions from decomp of organic matter.
Dissolved inorganic ions from weathering.

Question 4

Soil air: (7)

Answer 4

Most soils contain approx 25% air by volume.
Usually held in larger pores (water held in smaller pores).
Higher CO2 level than atmosphere because of plant respiration and decomp.
Lower O2 levels than atmosphere.
Oxygen tends to diffuse in and CO2 diffuse out.
Saturated with water vapour.
Some methane and nitrous oxide.