AP® Human Geography · Unit 5 · Topic 5.5
The Green Revolution
The Green Revolution was a mid-1900s package of high-yield seed varieties, synthetic fertilizer, and irrigation that multiplied crop output per hectare, turning countries like India from grain importers into exporters.
Starting in the 1940s and spreading through the 1960s, scientists bred new strains of wheat, rice, and corn with shorter, stronger stalks that could hold heavier grain loads without collapsing. These dwarf varieties responded strongly to synthetic nitrogen fertilizer, which older varieties could not use without toppling over. Pair the seeds and fertilizer with reliable irrigation, so the crop never stalls for lack of water, and a farmer gets two or three times the harvest from the same hectare. The three inputs work as a system: seeds alone do little without fertilizer, and fertilizer is wasted without steady water.
India is the standard case. In 1960 its wheat yield hovered near 0.85 tonnes per hectare. Government programs pushed high-yield seeds, built irrigation canals and tube wells, and subsidized fertilizer. By 2000 yields had climbed past 2.7 tonnes per hectare, and India shifted from a nation dependent on food aid to one exporting grain. That is roughly a 218 percent increase, found by subtracting the old yield from the new one, dividing by the old yield, and multiplying by 100.
The gains came with a cost that connects this topic to broader land-use patterns. Decades of pumping groundwater for irrigation have dropped water tables across Punjab and other breadbasket regions, and heavy fertilizer use has degraded soil structure and polluted waterways. Sub-Saharan Africa mostly missed the boom because the seed varieties were bred for Asian rice paddies and wheat belts, not Africa's soils, rainfall patterns, and staple crops like sorghum and cassava, and because farmers there often lacked access to irrigation infrastructure and affordable fertilizer to complete the package.
Key terms
- High-yield variety (HYV)
- A crop strain bred, often for short sturdy stalks, to produce far more grain than traditional varieties when given enough fertilizer and water.
- Percentage yield increase
- The change in yield divided by the starting yield, multiplied by 100.
- Green Revolution
- The mid-1900s spread of high-yield seeds, synthetic fertilizer, and irrigation that sharply raised crop output in much of Asia and Latin America.
- Groundwater depletion
- The long-term drop in underground water levels caused by pumping more water for irrigation than natural processes can replace.
Watch it explained
- How it worksHow do high-yield seeds, fertilizer, and irrigation multiply the output of one hectare?
- Worked exampleShow me India's wheat yield curve climbing from 1960 to 2000.
- Worked exampleFind the yield increase when output rises from 0.85 to 2.7 tonnes per hectare.
- Going furtherWhat happens to groundwater and soil after decades of Green Revolution intensification?
- Common mistakeWhy didn't the Green Revolution help sub-Saharan Africa the way it helped Asia?
Check yourself
End of topic.