Monday, April 8, 2019

How Much Do I Water?

Horticulture Hotline 04/08/19
By Bill Lamson-Scribner

If you have an irrigation system, check to make sure your heads are turning properly (not straight into the street or bubbling in the ground) and all your zones (valves) are working, or hire a professional to go through your system. The irrigation technician during a drought is like the lawn mower mechanic in March and April. Most likely you are going to have to wait for that house call. Right now they available.

During a drought, I will get these calls about “mysterious brown areas” in the lawn. The “mysterious brown areas” have in all cases turned out to be lack of water. Then I hear, “well I have been running my irrigation.” I then have to inform the person that their irrigation is not covering the whole yard. Money has been spent on fungicides and insecticides when all the area needed is a little water.

“My irrigation system runs for 20 minutes per zone three times per week, is that enough water?”  This is a type of question I get asked frequently, and the answer is not a yes or a no response.  Different irrigation systems have different gallon per minute nozzles so the rate varies according to the type of nozzle installed.  Water pressure also varies depending on where you live and whether you have a well.  Some irrigation heads pop up and mist and others pop up and spray in a rotary fashion.  The difference is enormous to a yard.  The pop ups that are spraying a constant mist can flood an area very quickly. The rotary head can run for an hour without too much water being applied. Rotary heads also can rotate 360 degrees or maybe only 180 degrees. The 180 degree heads would put out twice the water in a given area than the 360 degrees rotor in the same period of time. 

Ideally your soil should be moist down to six inches.  Moist…not saturated. Depending on your soil type, wind exposure, slope of yard, and exposure to sun, you will need differing amounts of water than other people in the Lowcountry. An old recommendation is an inch of water per week including rainfall. Of course this would vary if you lived in a windy, sunny, sandy soil, beach location compared to an inland shady, usually wet, and clay soil area.

A soil probe is an excellent way to determine the moisture levels in the soil.  Soil probes are available at garden centers.  Soil probes will allow you to check the moisture as well as the profile of your soil (see the layers of thatch, sand, clay, loam).  You can also determine how much thatch you have using these probes.  Soil probes also make taking a soil test much easier. 

Measuring the amount of water your sprinkler or irrigation system is putting onto your landscape is very easy.  A few coffee cups that have an equal diameter on top as the bottom is all you need.  If you are not a coffee cup person, you can also use tuna fish cans, soup cans or other containers that have an equal diameter on top and bottom.  If you don’t want to look like a hillbilly, you can invest in several rain gauges. 

Simply place these coffee cups throughout your lawn and run the sprinkler for 15 minutes, then measure the amount of water in the container.  If you have an irrigation system, you will have to measure each zone separately to get an accurate measurement. Place the coffee cups different distances from the head that you are measuring to see how evenly your heads are spraying. If heads from another zone are going to spray back into this area, you should collect that water too.   If you collected an average of a quarter inch of water in 15 minutes and you wanted to put out a half inch of water, simply increase your irrigation time to 30 minutes.

While you are out there, make sure you have good even coverage. Be sure the heads are turning properly and not pointed to the street. Are your trees and shrubs established to the point that you can turn off the zones that water them or are they in need of some pruning so they don’t block the water.

By applying organic products and/or wetting agents you can greatly reduce the amount of water you need to apply.  Cotton Burr compost is a great organic product that will reduce your watering bill, and increase the soil’s nutrient holding capacity making your fertilizers more effective.  Cotton Burr compost will also help reduce runoff of fertilizers and other control products into the environment because the products penetrate the soil. 

Wetting agents allow water to penetrate deeper into the soil resulting in deeper rooting grasses, plants, and trees.   Wetting agents will also help reduce runoff of fertilizers and other control products into the environment because the products penetrate the soil.   Although water is very inexpensive here compared to other parts of the country and world, you still don’t want to waste it.  Wetting agents have been shown to reduce water usage by 30-60%. I have been hugged by people that I sold wetting agents to and they returned to tell me about their savings on the water bill. Fungicide use can be reduced with less watering. 

The most important aspect of watering is keeping the soil moist to a depth of six inches.  Add the appropriate amount of water for your yard with your soil type, wind exposure, slope of yard, and exposure to sun. Adding organic products and wetting agents will help lower your water bill. 

Always read, understand and follow product label. The product label is a Federal Law.