Block 11: Nitrate & Pesticides

Question 1

When is nitrogen organic?

Answer 1

When bonded to carbon

Question 2

What are nitrogen immobilisation & mineralisation?

Answer 2

Immobilisation is the conversion of inorganic to organic nitrogen
Mineralisation is the conversion of organic to inorganic nitrogen

Question 3

What are denitirification, nitrification, & ammonification?

Answer 3

Denitrification is the reduction of nitrates into N2
Nitrification is the oxidation of ammonia to nitrite to nitrate
Ammonification is the reduction of organic nitrogen to ammonia or ammonium

Question 4

What processes cause oxidation of N2?

Answer 4

Lightning & high-temperature combustion reactions

Question 5

How do temporary grasslands increase nitrogen fertility?

Answer 5

Bacterial fixation of N2 into ammonia creates organic nitrogen to enrich the soils

Question 6

Describe solubility & adsorption trends of pesticides

Answer 6

Solubility: from ~0 to 100s ppm
Adsorption: mostly linear, controlled by carbon content of soils, described with Koc (low Koc > high solubility > low absorption)

Question 7

How does metabolism vary in soil?

Answer 7

Metabolism increases with increasing temperature & decreases with decreasing soil moisture
Optimal metabolic conditions are warm (not hot) & mildly damp
Metabolism is described by Ct & its half-life

Question 8

What soil management techniques can reduce the need for pesticides?

Answer 8

Riparian buffer zones, conservation tilling, temporary grassland fixation, restricting drainage