UGC NET Agricultural Greenhouse Gas Emissions & Mitigation: practice questions

1 · The AFOLU sector's share of global emissions · medium

Agriculture is the largest anthropogenic source of which pair of gases?

1. Carbon dioxide and methane
2. Nitrous oxide and refrigerant HFCs
3. Carbon dioxide and tropospheric ozone
4. Methane and nitrous oxide

2 · The AFOLU sector's share of global emissions · medium

Roughly how is the AFOLU total split between its two main components?

1. About half farm diesel use and half emissions from cold storage and food retail
2. About half land-use CO2, mainly deforestation, and half agricultural CH4 and N2O
3. About nine-tenths fertiliser manufacture and one-tenth enteric methane from all livestock
4. About one-tenth deforestation and nine-tenths soil carbon gains on all farmland

3 · Enteric methane and the rumen · medium

Which rumen fermentation product consumes metabolic hydrogen and is therefore associated with lower methane production?

1. Propionate
2. Acetate
3. Ammonia
4. Butyrate

4 · Manure management emissions: CH4 and N2O · medium

What does slurry acidification achieve?

1. Lower ammonia volatilisation and lower methane from stored slurry
2. Removal of all nitrogen from slurry, so spreading is no longer needed
3. Conversion of slurry to biochar without the need for any heating
4. Higher methane yield, so it is used to boost biogas output on farms

5 · Methane from flooded rice and alternate wetting and drying · medium

Why does incorporating fresh rice straw just before flooding raise methane emissions?

1. It lowers soil temperature, which speeds up methanogenesis in all flooded paddy soils
2. It blocks the aerenchyma, so methane stays in the soil and is released all at once
3. It supplies easily decomposed carbon to methanogens once the soil becomes anaerobic
4. It adds sulphate, which methanogens use as their main electron acceptor in soils

6 · Direct and indirect nitrous oxide from nitrogen inputs · medium

In nitrification, nitrous oxide is:

1. The final product of reducing nitrate to N2 gas
2. Absent, because nitrification is fully anaerobic
3. A by-product of oxidising ammonium to nitrate
4. A substrate that nitrifiers convert to ammonium

7 · Energy use and embedded emissions in inputs · medium

In a national GHG inventory, where are emissions from diesel used in farm machinery reported?

1. Agriculture sector
2. Not reported at all
3. Waste sector (landfill)
4. Energy sector

8 · Feed additives, breeding and herd management for lower emissions · medium

What is the main animal-health risk of feeding nitrate to reduce methane?

1. Iodine deficiency in calves
2. Bloat from excess propionate in the rumen fluid
3. Bromoform residues in milk and meat
4. Nitrite accumulation causing methaemoglobinaemia

9 · Nitrification inhibitors, precision nitrogen and 4R · hard

Which 4R element usually gives the largest single reduction in N2O on over-fertilised farms?

1. Right time, by applying everything before sowing
2. Right rate, by cutting surplus nitrogen
3. Right place, by broadcasting instead of banding
4. Right source, by switching all urea to nitrate

10 · Emission intensity versus absolute emissions; trade-offs with food security · medium

Which trade-off is most associated with afforesting farmland for carbon removal?

1. Higher fertiliser N2O per ha
2. More methane from rice paddies nearby
3. Competition with food production for land
4. Higher rumen methane per cow