Irrigation is to many people a daily chore and there are more or less convenient times during the day when this could be done. 

In order to minimize the water usage all logic tells you you should irrigate during night time. The reasons are many:

  1. The temperature and the wind speed is lower during night time.
  2. Night-time humidity is higher.
  3. No sun means no solar radiation.

Does that mean you should irrigate your lawn, plants or cultivation during night time?

ABSOLUTELY NOT!

Keeping your plants wet over night causes perfect conditions for fungus to grow. And unless you are using drip-irrigation or subsurface irrigation you will cause the foliage, flowers and fruit to become wet. 

If this wetness came during the day the water would evaporate but during nighttime the water will stay on the plant for an extended amount of time and result in fungi and bacteria having perfect condition for replication and invasion on the plant’s surfaces.

Does this mean that if you unlimited amount of water, then irrigating during daytime is the best?

If you ask this question to the average gardener or horticulturist then you will most often get a clear answer: 

ABSOLUTELY NOT! 

The explanation to this answer has been told from generation to generation – water drops on leaves create lenses that could cause leaf burn as a result of the intense focused sunlight.


Actually until recently there has not been much knowledge if there is any bearing to this. Gabor Horvath at Eotvos University, Budapest conducted researched on this and came to the conclusion that water drop on a leaf were not able to focus the sun’s energy sufficiently to damage the leaves before the water evaporated.
So all though you could irrigate during daytime, the best recommendation is to irrigate during early mornings, you get most of the advantages with night irrigation but reduces the chances of optimizing fungal growth. The moist will also keep the soil cool during the hottest hours of the day.