food and agriculture how to feed the ever expanding population currently 5.8 billion 30 years 12...

Food and Agriculture

How to feed the ever expanding population

Currently 5.8 billion30 years 12 billion

Modern methods in Agriculture

• Green Revolution

• Blue Revolution

What’s needed to grow food?

• soil - the outer weathered layer of the earth's crust. 

• Water

• Light

• nutrients

Soil contains both Biotic and Abiotic Components

• Topsoil is the upper 1 ft of land that is usable for plant growth

• Composition is clay:sand:silt defines the character of the soil

• Topsoil varies in different Biomes– Grasslands are the riches– Tropical Rainforest are some the poorest

BIOTIC ABIOTIC

HUMUS SILT (0.02-0.05mm)

Insect,

Worms

Nematodes

Sand (0.05-2 mm)

Bacteria

Protista

Symbiotes

Clay (<0.02 mm)

Charged

organic matter - typically about 1% in nature

litter - partially decayed organic matter on the soil surface. 

humus - highly decomposed, fine, amorphous organic matter in the soil. 

  Functions of Organic Matter:         1) stabilizes soil structure          2) increases water retention and availability          3) increases drainage and aeration          4) increases cation exchange capacity          5) supplies nutrients upon decay

(only if low C:N ratio)          6) stabilizes pH          7) food source for microorganisms 

• Bacteria and Fungi Decompose Organic Matter

• Micorrhizal Symbiotes (tree and fungi) enhance mineral uptake into plants

• Worms, Nematode and Insects decompose organic matter and aerate the soil

Soil Horizon

A Horizon or topsoil - highly weathered  - abundant life, therefore, high in organic    matter - dark colored     plow pan - a compacted impermeable                         layer in the A horizon due to                          repeated plowing or tilling                          (approx. 6" deep)

B Horizon or subsoil - less weathered; higher in clay  - less life, therefore, low in organic matter  - lighter colored     clay pan - impermeable layer high in clay.     hard pan - impermeable layer high in iron.

C Horizon or parent material - little weathered  - little life, except deep rooted plants and   little to no organic matter

D Horizon or bedrock - rock base

TYPICAL AGRICULTURAL SOIL Agriculturally productive soil is a balanced mixture of sand, silt, and clay.

Riches farming soils: grasslands (Mollisols) deciduous forest (Alfisols)

Land Degradation

• Overgrazing

• Deforestation

• Agricultural activities

• Overexploitation

• Industrialization

water and wind are the main

agents of erosion

Trees and Ground Cover Prevent erosion.

Why has 100 years of farming in the U.S. resulted in a loss of ½ of all cropland?

• Row crops

• Deep plowing

• Heavy herbicide use (no ground cover)

• Machine made gullies

• Chemical fertilizer

• No rotation of crops

• monoculture

• 72% of all fresh water (rivers, lakes and ground water) is used for irrigation

• Over-watering leads to– Loss of Oxygen– Salinization

Fertilizers Provide Inorganic Nutrients

• Major: N, K, P, C, Mg,S

• Applied Fertilizer– 1950: 20 kg/ha – 1990:91kg/ha

Phosphates and nitrates from farm field and cattle feed lots are aquatic pollutant.

Alternative Ways to Fertilize

• Manure

• Crop residues

• Ashes

• Composted refuse

• Green manure – *nitrogen fixing crops

Climate: The greenhouse effect

• Increasing CO2 increases productivity