What advances in farming occurred during the song dynasty

The Song dynasty if a period with the most extraordinary progress in China´s history.  One of the most important innovations in farming was the development and use of a new rice cultivation techniques and rice varieties. Examples: the early-ripening rice variety that allowed farmers to have two or three crops per year, thus increasing the amount of food available for human consumption; drought-resistant rice varieties; better systems of water control and irrigation.

Explanation:

because mexico wanted to choose a centralized location

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