Watering during a drought
By Tracey Payton Miller
OSU Horticulture Educator
I hate to dwell on doom and gloom, but the drought conditions and careless watering I have observed have made conservation one of my missions in life. Most of our available moisture is only in the top 4 inches of soil, and at 16 and 32 inches there is barely any water. At this point, our area of Oklahoma needs 24 to 28 inches of rain in the next 6 months to relieve the drought altogether. In addition, most of Oklahoma is classified as a D3 and D4 status according to the U.S. Drought monitor. These designations stand for extreme and exceptional drought --the highest drought levels possible. These stats are sobering going into the hot summer season. What can you do?
This time of year, you should only be watering mature trees and shrubs--no lawns, no gardens, nothing that isn't actively growing right now. Shrubs and newly planted trees need 1 to 2 inches of water every few weeks. Mature trees can take 1 to 3 inches of water, from a slowly running hose, at the dripline. Water mature trees every month or two. In the next couple months, as lawns and gardens begin to wake up and be planted, water no more than 1 inch per week, in one application. So pick a day, apply your water, and be done. This goes for annuals, perennials, vegetables, and lawns. Watering more than this will create more dependent, shallow root systems. Shallow root systems will not survive the drought unless you are responsible for all the water the plants receive. To measure when your watering system reaches the 1 inch amount, use a tuna can. Time how long it takes to fill it up, then you have a system in place to apply the necessary water.
Lawns are the biggest water waster in the landscape. Stick to the 1 inch rule, or better yet, let your Bermudagrass go dormant during the summer. In addition, leave the grass longer as the season warms. Grass is a living mulch and provides some of the same benefits as traditional mulches. I encourage those with fescue lawns to let them go. It is counterproductive to baby a cool-season, water hogging lawn through 100 degree temperatures in a drought. Use a mulch layer under shade trees instead. You may consider minimizing some large turf areas and replacing them with low water use flower beds.
When you do decide to water, hand water as little as possible and water early in the day. This ensures less water is lost to evapotranspiration. Any type of above ground sprayers or sprinklers are very inefficient, so use soaker or drip hoses wherever you can. In addition, know how to operate your sprinklers and change them with the season. I've seen way too many frozen sprinkler heads and sprinklers running during a rainstorm. Sensors are available to prevent watering during a rain. Draining ponds and using well water carelessly is no excuse. Fertilizer and herbicide applications shouldn't be applied to drought stressed plants. But, if think you just have to fertilize, do it right before applying your 1 inch of water. This will limit the amount lost to runoff when timed with rain events. After mowing, don't hose off cement or other areas. Instead use a broom or leaf blower.
Soil improvements can be made to help improve water infiltration and retention. Don't till if you can help it. Tilling breaks down the soil profile and decreases pore space where air and water reside. In addition, add organic matter, in the form of compost, to the soil. Adding compost is the best way to improve clay soils and increase pore space. Use 1 to 2 inches of compost as a mulch, or underneath a thin layer of bark mulch. You must mulch any plants you want to keep, this is essential. Mulch cools the soil, moderates soil temperature fluctuations, suppresses weeds, and helps retain soil moisture. Also, limit soil compaction as much as possible, by building raised garden beds you can reach across. If you have to walk in your beds, do it when the soil is drier and keep it short.
Additional drought and weather information can be found at mesonet.org and droughtmonitor.unl.edu.