Agriculture and food practice questions.

The package of changes usually described as the Green Revolution combined

• high-yielding cereal varieties with irrigation and inorganic fertiliser
• organic manure with crop rotation and reduced tillage on smallholdings
• genetically modified crops with drip irrigation and integrated pest management
• terracing with agroforestry and locally saved traditional seed varieties

Answer: high-yielding cereal varieties with irrigation and inorganic fertiliser

High-yielding dwarf varieties only out-yield traditional ones when water and nutrients are not limiting, so irrigation and fertiliser were part of the same package. That dependence is also why the yield gains came with groundwater depletion and salinisation in regions such as Punjab, India.

A 4 000 hectare cattle ranch on the Argentine pampas is worked by three people, buys in no supplementary feed and sells its beef for export. This system is best classified as

• Intensive and subsistence
• Intensive and commercial
• Extensive and subsistence
• Extensive and commercial

Answer: Extensive and commercial

Intensity refers to the inputs applied per unit area, not to the size of the holding, and three workers with no bought feed across 4 000 hectares is a very low input per hectare. Because the output is sold rather than eaten by the producers, the system is commercial.

A vegetable grower counts pest numbers weekly, releases a predatory mite once a threshold is crossed and sprays a chemical only if the predator fails. This approach is best described as

• prophylactic broad-spectrum pesticide use
• integrated pest management
• monoculture intensification
• biological control used on its own

Answer: integrated pest management

Integrated pest management combines monitoring, action thresholds and biological control and keeps chemicals as a last resort. Releasing the predator alone would be biological control, and spraying to a calendar regardless of pest numbers is prophylactic use.

Which change to an intensive arable system would most directly reduce nitrate leaching into a neighbouring stream?

• sowing a cover crop to take up residual nitrogen after harvest
• increasing the depth of ploughing before the crop is sown
• raising the stocking density of livestock on the adjacent pasture
• applying the same total fertiliser in a single dose before sowing

Answer: sowing a cover crop to take up residual nitrogen after harvest

Nitrate leaches whenever it sits in the soil with no living roots to take it up, so keeping a crop cover between harvests is the direct control. A single large dose before sowing does the opposite, because uptake is lowest when the crop is smallest.

A retailer compares two supplies of tomatoes: one grown in a heated glasshouse 50 km from the shop, the other grown in open fields 2 000 km away and brought by road. Assessments of this kind repeatedly show that

• the shorter journey always gives the lower total energy use per kilogram
• the two supplies use the same energy per kilogram delivered
• transport distance alone is a poor guide to total energy use
• energy use depends only on the type of vehicle used

Answer: transport distance alone is a poor guide to total energy use

Heating a glasshouse through a temperate winter typically dwarfs the fuel used to move the crop, so the local supply can carry the larger footprint. The general lesson is that a life-cycle comparison has to include production, and that food miles measure only one term of it.

A government requires that a fixed share of transport fuel be produced from maize ethanol, and growers respond by selling more of the harvest to distilleries. The group most directly disadvantaged by this change is

• households that buy maize as a staple food
• maize growers, whose grain now has fewer possible buyers than it had before the rule
• distillery operators, who lose the guaranteed share of the fuel market that the rule creates
• owners of maize land, whose land earns less once a fuel demand is added to a food demand

Answer: households that buy maize as a staple food

The same harvest is now claimed by two uses, so growers and landowners gain while people who buy maize to eat face a tighter supply at a higher price. Naming who gains and who bears the cost is the required answer; an intervention of this kind is not simply good or bad for everyone.