Dirt

1. -One tablespoon of healthy dirt can contain up to 9 billion microorganisms.
    -One acre of healthy topsoil can contain 900 pounds of earth worms, 2400 pounds of fungi, 1500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of anthropods and algae, and even small mammals.

2. Carbon is the "glue" that holds everything in healthy soil together. If you take away the carbon everything falls apart, and unfortunately in many parts of the world the carbon, or "glue", in soil is deteriorating rapidly due to soil erosion, compaction, salinity, and loss of fertility.

3. Throughout history, mankind's greatest civilizations have grown where soil is fertile enough to support high density populations of humans, and have fallen due to land degradation. Examples of these civilizations are the ancient: Greeks, Mesopotamian's, and Mayans

I recently watched a video on TED.com about "window farming" where plants are suspended in clay pellets and hung in windows while pumps circulate a nutrient rich solution through each one. In this method of growing no soil is used at all, and the farmers managed to grow a wide variety of crops such as cucumbers, cherry tomatoes, and more. I wonder how many types of crops could actually successfully be grown in this kind of system on a regular basis, and what the limitations, if any, there are in window farming.

link to the video:
http://www.ted.com/talks/britta_riley_a_garden_in_my_apartment.html