How did the production technology of intercropping and interplanting improve the multiple cropping index develop in ancient vegetable production in China?

Intercropping and interplanting to improve multiple cropping index was first developed in vegetable production.

In the Western Han Dynasty, there was a custom of making kudzu and agastache in the central part of Gua Tian. In the Northern and Southern Dynasties, not only one vegetable was planted or interplanted with another vegetable, but also vegetables were interplanted with field crops. By the Qing Dynasty, there had been interplanting of vegetables with food crops and cash crops.