As part of our book club I read Dirt: The Erosion of Civilizations
and was impressed. My father was careful to distinguish between dirt and soil. Soil has structure with layers. Dirt is unstructured.The book starts with research from Charles Darwin focusing on the the positive effect of earthworm castings on the building up the depth of soil structure. This is good for some parts of the world but not so good in certain forested areas.
How civilizations practice agriculture and take care of the soil affects their sustainability and survivability. When cultures increase the use of the soil without crop rotation or letting it rest the productivity of the soil declines. Erosion increases the loss of top soil and reduces the ability of plants to grow on the soil. Irrigation often increases the amount of salt in the soil which reduces the types of plants that can grow crops. Egypt and North Africa supplied grain for the Roman Empire because the farming practices of Rome eroded the top soil and made the land unproductive.
Cutting down trees and planting on hillsides is a prescription for rapid soil loss and subsequent transition out of productive farm land. Agricultural practices will need to change, crop rotation with nitrogen fixing plants. Mixing in organic matter with soils. Using low till or no seed drills will also extend the useful life of the soil. He points to the organic farming method used in Cuba out of necessity because they lacked access to chemical fertilizer or pesticides.
For those of you who want a touch of optimism feel free to explore the work being done by the Land Institute. They are working on developing perennial crops which put less stress on the soil. The University of Minnesota is also researching the perennial grain kernza as part of sustainable cropping system.
Bringing our soil back to life - 66 min.
Soil degradation and why you should care - 27 min.
Can we reverse the long term pattern of soil degradation - 17 min.
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