How does China agronomy comprehensively use various means to grasp the farming season?

China agronomy does not rely solely on one means to grasp agricultural time, but uses a variety of means to form a time indicator system. For example, Shangshu Yaodian takes the appearance of birds, fire, sky and long stars at dusk as the symbol of the four seasons, and also records the dynamic changes of birds and beasts in the four seasons.

Another example is Xia He's Book of Rites and Moon Order, although it was written late, but it retains a lot of ancient contents, and all of them list the monthly degrees of the moon, sun and stars, meteorology and phenology as the basis for arranging farming activities, which actually covers most of the 24 solar terms. This has become the tradition of monthly agricultural books.

The formation of the 24 solar terms does not exclude other timing methods. At the same time of its formation, people sorted out 72 phases used in cooperation with it on the basis of the accumulation of ancient phenological knowledge. It enriches the means of time indication in traditional agronomy in China.

Twenty-four solar terms, as the main timing means of Chinese traditional agriculture, cooperate with other means to complete its tasks.

Wang Zhen, an agronomist in the Yuan Dynasty, recorded in his Agricultural Book:

Twenty-eight nights, the change of Sunday, the meeting of the sun and the moon on the twelfth, the passage of twenty-four qi, and the change of seventy-two seasons, such as the circle of circulation, such as the turning of the wheel and the festival of agriculture and mulberry, are accounted for.

To this end, Wang Zhen has also produced a "seasonal picture", which summarizes the stars, solar terms and phenology in one picture, and determines the month according to the 24 solar terms, so as to arrange monthly farming.

He also pointed out that maps should be used flexibly according to the specific conditions of each place, and they should not be rigid and inflexible. This is a summary of China's agricultural time index system.