1. Crops and Soil

2. Arable Land Land that can be used to grow crops
As the human population increases, the amount of arable land decreases

3. Basic Processes of Farming
Plowing
Fertilization
Irrigation
Pest control

4. Traditional Agriculture
Plows pushed by farmers or pulled by livestock
Organic (manure and plant waste) fertilizers used
Fields irrigated by flowing water in ditches
Weeds removed by hand or machine

5. Modern Agriculture
Machines powered by fossil fuels for plowing and harvesting crops
Synthetic chemical fertilizers used
Overhead sprinklers and drip irrigation used
Synthetic chemicals used to kill pests

6. Soil Fertile Soil: soil that can support the growth of healthy plants
Soil forms when rock is broken down into smaller fragments by wind, water, and chemical weathering
Can take hundreds or thousands of years to form just a few centimeters of soil

7. Soil Rock particles add mineral nutrients
Decomposed dead plant matter add more nutrients
Earthworms, insects, and small animals break up soil and allow air and water into it
Helps plants grow

8. Soil Erosion
Erosion- the wearing away of rock or soil by wind and water
About half of the original topsoil in the U.S. has been lost to erosion in the past 200 years
Almost all farming methods increase the rate of soil erosion

9. Land Degradation
Occurs when human activity or natural processes damage the land so that it can no longer support the local ecosystem

10. Desertification
Process by which land in arid or semiarid areas becomes more desertlike because of human activities or climate change
Causing some arable land to disappear
Often from too many crops planted too frequently and overgrazing

11. Soil Conservation Protects and manages topsoil and reduces erosion
Soil usually erodes downhill
Many soil conservation methods designed to prevent downhill erosion

12. Soil Conservation Methods
Soil retaining terraces built across a hillside
Contour plowing
Windrows
Catch soil and water
No till farming
Areas may be better suited for forests or grazing land

13. Enriching the Soil Traditionally organic
Inorganic fertilizers used to double world food production
Often pollute water through runoff

14. Modern Soil Enhancement
Use both organic and inorganic fertilizers by adding compost and chemical fertilizers to the soil
Compost: partly decomposed organic material

15. Salinization The accumulation of salts in the soil
Major problem in areas with low rainfall and naturally salty soil
Irrigation water comes from rivers or groundwater which is saltier than rainwater
When the water evaporates, the salts are left behind
The soil may become too salty to support plants
May be slowed if irrigation canals are lined to prevent water from seeping in to the soil or water the soil heavily to wash out the salts

16. Salinization

17. How can you protect our soil?