The Nitrogen Cycle

Question 1

The nitrogen cycle importance

Answer 1

essential to understand in agricultural systems for making N fertiliser recommendations which meet requirements of crops without polluting water bodies or the atmosphere

Question 2

Nitrification

Answer 2

autotrophic bacteria that are sensitive to soil conditions

• nitrosomanas
• nitrobacter

Question 3

Ammonification (N Mineralisation)

Answer 3

proteins = peptides = amino acids = NH4+

Question 4

requirements of nitrifiers

Answer 4

• soil pH (4.5-7.5)
• soil moisture and aeration (field capacity)
• soil temp (25-30)
• soil nutrient status, fertiliser applications and other agrochemicals

Question 5

leaching losses of No3-

Answer 5

• season
• soil type
• land use

Question 6

Denitrification

Answer 6

wide range of microorganisms
- occur in anaerobic conditions (O2 low), including localised zones within soil profile
REQUIREMENTS
- available C source
- soil pH: no less than 5
- soil temp: very slow <10 stops <2

Question 7

Ammonia volatilization

Answer 7

• occurs during formation of NH4+ by ammonification under alkaline conditions

Question 8

Immobilization

Answer 8

the conversion of inorganic compounds to organic compounds by micro-organisms or plants, by which it is prevented from being accessible to plants

Question 9

Mineralization

Answer 9

The decomposition (oxidation) of the chemical compounds in organic matter, by which the nutrients in those compounds are released in soluble inorganic forms that nay be available to plants