Regulated deficit irrigation (RDI) is a useful method for saving water while still providing enough water for citrus plants to grow well. This review looked at different ways RDI is used in citrus farming and how to tell if plants need more water. Most methods for deciding when to water citrus plants are complicated and need a lot of data, but using a tool called a time domain reflectometer (TDR) can make it easier to know when to water. The review suggests that using TDR can help farmers give their citrus trees the right amount of water to grow efficiently.