春秋战国以后随着铁制农具的出现，农业生产对季节性的要求更高了，就逐渐形成了节气的概念。

During the Spring and Autumn Period, the agricultural production was highly subject to the seasonal changes with the invention of iron tools, thus forming the concept of Solar Term.

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农民用买来的工具生产出的等价商品交换铁制的和木制的农具。

Metal and wooden tools are purchased with a commodity of equal value, produced using the tools acquired by the trade.

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农民用买来的工具生产出的等价商品交换铁制的和木制的农具。

Metal and wooden tools are purchased with a commodity of equal value, produced using the tools acquired by the trade.

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