The researchers looked at how often farmers grow crops in a specific area in China over many years. They wanted to understand different ways of planting crops and how it affects the land. Instead of just counting how many times a crop is harvested each year, they created a new method called Multiple Cropping System (MCS) to see the whole picture of crop use. By studying satellite images from 2001 to 2018, they mapped out four main crop systems, with some areas growing one crop a year and others growing more in a cycle. They found that most fields followed a pattern of planting two crops a year, and this new method can help farmers plan better ways to use their land for growing crops efficiently.