"There was no rain and drought in March, and the wheat seedlings died without showing up. In September, first frost is cold in autumn and the ears are green and withered. " No rain in March does not mean that there is no rain for a whole month in March of the lunar calendar, but there is no rain and snow for three consecutive months from the winter of 808 to the following spring. According to historical records, it didn't rain properly until March this year. To this end, Bai Juyi also wrote a song "Yu He" to express his happy mood at that time. In the days when people depend on the weather, the winter wheat planted in Ling Du, a suburb of Chang 'an, is not moistened by a drop of rain from sowing to turning green. As a result, most of them dried up and died before they reached their ears. Since there is no harvest in summer, we can only count on autumn grain. However, farmers never expected that the early arrival of frost in late autumn and early September would make the poor wish of "Du Lingcuo" come to nothing again, and all the autumn crops in the field would freeze to death before they were mature. There is almost no grain harvest in the two seasons, which is Bai Juyi's explanation of "the dilemma of farmers" and "the dilemma of natural disasters" in the preface. In this song "Ling Du Wrong", he even wrote: "If you mistreat others and hurt others, you are a wolf. Why do you have to grab your teeth and eat human flesh! " When Bai Juyi wrote the above complaint with indignation, he did not realize that he had actually touched the cruel and barbaric social essence of cannibalism in feudal society. In fact, whenever the famine is serious, the emperor issued a letter to rent-free and tax-free, and local officials stepped up exploitation and extortion, but it was just a double-reed play.