anthropology question?

Slash and burn is a short term technique in agriculture that makes an area of land intensely fertile by cutting down the wild vegetation and burning the thatch into ashes. This only lasts for a handful of years until the soil is depleted and requires moving to a new area to repeat the process while allowing the former land to fallow and replenish. Hence the term shifting cultivation.

The longer a field is cropped, the greater the loss of soil organic matter, cation-exchange-capacity and in nitrogen and phosphorus, the greater the increase in acidity, the more likely soil porosity and infiltration capacity is reduced and the greater the loss of seeds of naturally occurring plant species from soil seed banks. In a stable shifting cultivation system, the fallow is long enough for the natural vegetation to recover to the state that it was in before it was cleared, and for the soil to recover to the condition it was in before cropping began. During fallow periods soil temperatures are lower, wind and water erosion is much reduced, nutrient cycling becomes closed again, nutrients are extracted from the subsoil, soil fauna decreases, acidity is reduced, soil structure, texture and moisture characteristics improve and seed banks are replenished.