We have no guarantees that this wet year will be followed by others that will continue to fill our storage lakes and replenish our seriously depleted underground aquifers. Home gardeners’ conservation efforts had a real effect during the last four drought years. It’s just common sense to continue conserving water. Here are some tips for better irrigation.
Lawns – In May, Bermuda grass lawns need on average 66 minutes of irrigation per week to remain healthy; in June, they require 82 minutes of watering per week. The amount of water required to keep fairly drought-tolerant Bermuda lawns green follows rises and dips in temperature. Many gardeners set their timers just once or twice a year but those who are serious about water conservation check the weather report every few days and adjust irrigation timers accordingly especially during spring and fall when wide temperature swings are common.
Plants and trees – Some plants and trees are thirstier than others. With good planning, drought-tolerant and less thirsty plants can and should be grouped together in the same irrigation zones in the landscape. If they’re not clustered so that irrigation times can be adjusted to their lesser water needs, consider redesigning your irrigation system to create separate zones.
Thirstier plants and trees should also have their own zone, but that isn’t always practical. Vegetable planting beds often hold a wide variety of plants with very different requirements. Shallow-rooted cucumbers and beans will need far less water than tomatoes which need about 2 gallons per week. Keep a watering can or hose with a shutoff nozzle close to your tomatoes or other thirstier plants and irrigate them whenever the top 2 inches of soil is dry.
The roots of citrus and redwood trees should be kept consistently moist in summer at a depth of 4 inches. The water from lawn sprinklers only penetrates about 2 to 3 inches deep. Thirty percent to 70 percent of the water sprayed into the air by overhead lawn sprinklers is lost to evaporation on hot days depending on the size of the water droplets, humidity levels and the time of day. Get the water where it needs to go by using bubblers, drip emitters or soaker hoses, which direct water to the roots and can be connected to irrigation timers. The hoses may need to be attached to a separate timer located on the hose nib or valve.
Mulch – Bare, unmulched soil can quickly lose 100 percent of its water content through evaporation on hot days since water wicks upward – away from plants’ roots toward the dry top soil. A 4-inch layer of mulch can reduce the amount of evaporation by at least 70 percent.
Amending the soil to improve drainage and water retention capacity is a lesser-known water conservation measure. Soil that is heavily amended with organic compost and humus on a regular basis doesn’t form a dried-out top crust that becomes impermeable to water. Experiments at UC Davis have measured significant reduction in water loss from runoff on well-amended soil. Regular additions of organic compost and humus turned into planting beds twice a year in large amounts and applied as fertilizer in smaller amounts create living soils that keep our plants healthy in our dry, arid climate.
Send Elinor Teague plant questions at firstname.lastname@example.org.