Many folks have been very challenged this summer with plants that have not been doing well. These plants are showing signs of water and nutrient deficiencies, as well as plant support. As these questions come in, many of the folks talk about how they water every morning a small amount and there are folks that even go further and apply water twice a day every day. This is just too much love!
Please think about this with me for a minute... Typically folks that are approaching their watering often perform this task in small amounts. So, I ask, how deep do we get the water down in the soil profile? The answer is about an inch or two. So, if the moisture is only in the top two inches, which direction do you think the roots will grow? Up! This gives the plant less area for the roots to collect moisture, nutrients, and provide support for the plant. This also occurs in field grown crops as well. Damp springs with continuous rainfall are years when we see the most nutrient deficiencies (soybean iron chlorosis), drought stressed corn (when wet spring is followed by dry summer or fall) and corn that blows down in a mild wind event (due to lack of structure support).
This leads me to my key points for being a more successful gardener during dry period, while saving water due to better water use efficiency:
Research shows "most" plants need about 1" of moisture weekly so think about how it can be delivered - Once a week, twice a week, or spoon fed daily. In the case, watering less frequently is better. Once a week is just fine. This is especially true of course soils like sand and gravel. This will drive the roots deep. This is especially true with trees and shrubs.
Another reason to water less frequently is in the case of disease, especially if you are using a sprinkler. Periods of excessive dampness with both natural (rain or dew) or irrigation increase the risk of development of disease, therefore, the suggestion is to irrigate in the morning before the dew is off so as to not increase the time that the plants are wet. This practice once a week and proper pruning to increase airflow all help in reducing the disease risk.
There are, of course, many more details related to watering for conservation:
-Troy Salzer, UMN Ag Extension Educator