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