Crops and Soil

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

Basic Processes of Farming Plowing Fertilization Irrigation Pest control

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

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

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

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

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

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

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

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

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

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

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

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

Salinization

How can you protect our soil?