Why do irrigators irrigate during the day?
Irrigating at night does stop evaporative losses caused by the sun. For a well-designed irrigation system, evaporative losses caused by irrigating during daylight are minimal (less than 3%). To design an irrigation system than only operates 12 hours a day would be cost prohibitive. The farm would have to double the amount of irrigators, and the water supply system would have to double its capacity. The electricity lines used would also have to double their capacity!