What are the characteristics of farming in the first frost period?

"When paraquat passed through the first frost, it was not too late to collect potatoes." After the first frost, most areas in southern China began to collect and dig a lot of sweet potatoes. After the first frost, this kind of farmland soil has been planted in vast areas of northern China, and some farmland will be in the winter leisure period. After the first frost in North China, it is time to harvest Chinese cabbage.