During what period did the nomads of central asia have an effect on the other global civilizations of the eastern hemisphere during the postclassical era?

crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.

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john maynrd keynes developed new economic respose to the                           ( b. great depression if the 1930's)