What is the most common method of applying wastewater to land?

Spray irrigation is the most common method of applying wastewater to land due to its efficiency in achieving uniform distribution of water across large areas. This system involves using pumps to spray treated wastewater over crops, which facilitates quick absorption into the soil and ensures that the nutrients in the wastewater are effectively utilized by plants.

This method is particularly advantageous because it minimizes waterlogging and allows greater control over the amount of water applied, which can be critical in optimizing water and nutrient uptake by plants. It also helps in preventing runoff and potential environmental contamination.

In contrast, the other methods—such as surface flooding, drip irrigation, and subsurface irrigation—are used in specific situations or for particular types of crops but do not match the widespread application and versatility of spray irrigation for land application of wastewater.