Four natural factors that shape farming
A plant needs warmth, water, light and good soil. A farmer also needs land that can be ploughed.
- Relief (the shape of the land): flat land is easy to plough and water. Steep slopes lose soil, so farmers cut steps called terraces.
- Temperature: crops need a long enough warm season to ripen.
- Water: from rain, rivers, wells or canals. Too little means drought; too much, flood.
- Soil: deep, loose soil with plant food (river mud, called alluvium) is best.
Climate means the usual weather over many years. Rainfall and temperature together are the biggest actors.
Warm temperate and temperate plains: dry farming
On cool plains with moderate rain (about 500 to 800 mm) the main crops are wheat, maize (corn) and millet. This is dry farming: the farmer depends mostly on rainfall and stored soil moisture, not on flooded fields. Winters are cold, summers warm. Flat land lets tractors and harvesters work, so farms can be large. Where rain is uncertain, farmers add wells or canals to save the crop in a dry spell.
Subtropical and tropical lowlands: paddy rice and water networks
Warm weather all year and heavy rain (above about 1000 mm) suit paddy rice. Rice seedlings grow best in a few centimetres of standing water, so farmers build small walls (bunds) around flat fields. Rivers and lakes spread across the plain, so people dig channels, ponds and canals: a water network. With so much heat and water, two or even three crops a year are possible. Sugarcane, tea and fish ponds often sit beside the rice.
Arid land: oasis, irrigation farming and grassland herding
An arid climate has under about 250 mm of rain. Plants cannot grow without extra water, so farming is only possible at an oasis (a place where groundwater or a mountain stream reaches the surface) or along irrigation canals and wells. The rest is dry grass or desert, used for herding: sheep, goats and camels walk to fresh grass with the seasons. Drip pipes save water, and crops like dates, cotton and melons suit the sun.
High and cold land: highland farming and herding
On a high plateau the air is thin, summers are short and nights can freeze. Only hardy crops such as highland barley, potatoes and peas ripen. Farmers grow them on low, sunny valley floors and on terraces cut into slopes. Higher up, grass is the only crop, so people herd yaks and sheep for milk, wool and meat. Because slopes are steep and soil is thin, protecting the soil is as important as the harvest.
Try it: predict, then check
Pick any dish you ate today. Name its main plant. Which of the four region types would grow it best, and why? Then use the rainfall slider in the 3D and see at what rainfall your crop appears. Good guessers say the reason in the form: "This crop needs ___ , and that region gives ___ ."
Key formulas and definitions
- Key terms: relief = shape of land; climate = usual weather over many years
- Dry farming = growing crops mostly on rain (about 500 to 800 mm)
- Paddy rice = rice grown in standing water (heavy rain, flat land)
- Oasis = a green spot in a desert where water reaches the surface
- Herding = keeping grazing animals such as sheep, yaks, camels
- Average monthly rain = yearly rain / 12
Worked examples
1. A plain gets 650 mm of rain a year and cold winters. Name two likely crops and the farming type.
Moderate rain with cold winters suits wheat and maize. The farming type is dry farming, because it depends on rain and soil moisture.
2. A valley has 1300 mm of rain, flat river mud and hot summers. What is the main crop and why does it need small walls around fields?
Paddy rice. Rice seedlings grow best in a few centimetres of standing water, so small walls (bunds) hold the water in the flat field.
3. A desert village has green fields in a ring around a spring. Explain what this is and how the rest of the land is used.
It is an oasis, because water reaches the surface there so crops can grow. The rest of the dry land has only sparse grass, so it is used for herding sheep, goats or camels.
4. Why do farmers on a steep, cold plateau cut terraces?
A terrace is a flat step on a slope. It keeps rain from washing the thin soil away and gives level ground for hardy crops like highland barley.
5. A town gets 900 mm of rain a year. What is its average rainfall per month, and can we be sure rice will do well?
900 / 12 = 75 mm per month on average. Not sure: rainfall may fall in only a few months, and rice also needs flat land and heat. Distribution through the year matters, not only the total.
Common mistakes
- Saying climate is the only factor. Relief and soil matter too: a rainy steep slope still loses its soil.
- Mixing up dry farming with desert farming. Dry farming happens in places with moderate rain; desert farming needs irrigation.
- Thinking rice grows anywhere warm. It also needs lots of water and flat land.
- Forgetting that herding is farming too. In dry or high lands, animals are often the main living.