Physical factors also affect agriculture. Image credit

ZIMSEC O Level Geography Notes:Agriculture:Factors influencing farming: Physical or Environmental factors


  • These are critical for plant growth because each plant or crop type requires a minimum growing temperature.
  • In temperate latitudes this is 6°C. Below this members of the grass family, including cereals, cannot grow.

Growing season

  • Growing Season is the number of days between the last frost of spring and first frost of autumn.
  • Growing season varies by crop; Cotton needs 200, Spring Wheat needs 90.

Rainfall/water supply

  • The mean annual rainfall for an area determines whether farming is likely to be based upon tree crops, grass, cereals or irrigation.
  • Few crops can grow when there is less than 250mm a year.
  • Seasonal distribution is more significant than annual total rainfall.
  • Long steady periods of rain allow the water to soak into the soil.
  • Short heavy downpours lead to surface runoff and soil erosion.


  • Growth is controlled by decrease in temperature at height.
  • In Britain few grasses (including hay) can produce commercial yields above 300m.
  • In warmer latitudes wheat can ripen at 3000m.


  • Wind increases evapotranspiration rate.
  • This allows the soil to dry out and to become vulnerable to erosion.
  • Some winds are beneficial to agriculture, for example Chinook.
  • Chinook winds are a warm dry wind which blows down the east side of the Rocky Mountains in Canada at the end of winter.
  • This melts snow on the prairies, lengthening the growing season.

To access more topics go to the O Level Geography Notes page