1. Food and Agriculture How to feed the ever expanding population Currently 5.8 billion 30 years 12 billion

2. Modern methods in Agriculture Green Revolution Blue Revolution

3. What’s needed to grow food? soil - the outer weathered layer of the earth's crust. Water Light nutrients

4. 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

5. BIOTICABIOTIC HUMUSSILT (0.02-0.05mm) Insect, Worms Nematodes Sand (0.05-2 mm) Bacteria Protista Symbiotes Clay (<0.02 mm) Charged

6. 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.

7. 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

8. 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

10. Soil Horizon

11. 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

12. TYPICAL AGRICULTURAL SOIL Agriculturally productive soil is a balanced mixture of sand, silt, and clay. Riches farming soils: grasslands (Mollisols) deciduous forest (Alfisols)

14. Land Degradation Overgrazing Deforestation Agricultural activities Overexploitation Industrialization

15. water and wind are the main agents of erosion Trees and Ground Cover Prevent erosion.

16. 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

17. 72% of all fresh water (rivers, lakes and ground water) is used for irrigation Over-watering leads to –Loss of Oxygen –Salinization

18. 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.

19. Alternative Ways to Fertilize Manure Crop residues Ashes Composted refuse Green manure –*nitrogen fixing crops

20. Climate: The greenhouse effect Increasing CO 2 increases productivity