Sustainable Food Production

Questions for Today:

• What is Soil?

• What is Soil Erosion?

• What is desertification, salinization, waterlogging?

• What are ways to reduce Soil Erosion?

• How do you restore Soil Fertility?

What is Soil?

• Soil is a relatively thin surface layer of the Earth’s crust consisting of mineral and organic matter that is affected by agents such as weather, wind, water, and organisms.

• Three components of soil:– Clay, Silt, and sand.

Soil Horizons

• Soil is a slowly renewed resource that provides most of the nutrients needed for plant growth and also helps purify water.

• Mature soils, or soils that have developed over a long time are arranged in a series of horizontal layers called soil horizons.

• Four Horizons– O, A, B, C

Soil Erosion

• Producing Food has major environmental impacts.

• It can degrade:– Biodiversity– Soil– Water– Air– Human Health

Soil Erosion

• Soil Erosion is the movement of soil components, especially surface litter and topsoil, from one place to another by the actions of wind or water.

• Soil Erosion has two harmful effects:– The Loss of Soil Fertility– Water pollution

Desertification

• Desertification is the loss of productivity in a given area due to drought and/or human activities.– Occurs generally in

arid or semiarid climates

– Usually due to the loss of topsoil.

Salinization and Waterlogging

• Both Salinization and Waterlogging deal with irrigation of crop lands.

• When we irrigate crops, some of water absorb the different salts in the ground water.

• As the water evaporates, the salt is left behind in the topsoil.

• Over-irrigation can lead to a salinization of the topsoil which would render the soil “sterile”.

Salinization and Waterlogging

• Irrigation can also lead to waterlogging.• Waterlogging is, in essence, the opposite

of salinization.• It occurs when farmers apply large

amounts of water to leach salts deeper into the soil away from the topsoil.

• If proper drainage does not exist, the saline water chokes out the deep roots killing the plant.

Fig. 13-13, p. 281

EvaporationTranspiration

EvaporationEvaporation

Waterlogging

Salinization Waterlogging1. Irrigation water contains small amounts of dissolved salts

2. Evaporation and transpiration leave salts behind.

3. Salt builds up in soil.

1. Precipitation and irrigation water percolate downward.

2. Water table rises.

Less permeable clay layer

Soil Conservation

• There are many ways to prevent soil degradation in the world. There are four methods employed today:– Terracing– Contour planting and strip cropping– Alley Cropping– Windbreaks

Soil Fertility

• One of the major degradation done through agriculture is nutrient loss in the topsoil.

• The number one method to increase soil fertility is through the use of fertilizers.– Organic Fertilizers

• Manure (Animal and Green)• Compost

– Commercial Inorganic Fertilizers• Fertilizers rich in nitrogen, phosphorus, and potassium