Knowing your soil type and average weather will enable you to gauge the best time to water your soil. Experiment with what works best in your area, keep good records and develop a regular watering schedule.
The signs of a well-cared-for yard are a green, weed-free lawn, healthy trees and healthy shrubs. They are an investment in the value of your property and should be protected.
The question of how much to water and how often has no single answer. It depends on weather conditions, soil composition and the plants themselves.
1. Weather — On a hot, sunny day in midsummer, the average lawn uses 125 gallons of water per 1,000 square feet. The same lawn on a cool, cloudy day uses as little as 10 gallons of water. Mature trees can use up to 15 gallons of water per hour on a hot day. Any plant exposed to hot sun, low humidity and strong winds will evaporate large amounts of water that must be replaced from the soil or it will die. Grass is particularly susceptible since 85% of its bulk is water.
2. The Plants — A good drenching once or twice a week is better for your lawn than daily light sprinklings. Deep watering produces strong, deep root systems that can safely withstand drought. This requires a long, thorough soaking of the soil, ideally to a depth of about 1 foot but at least 6 to 8 inches. A steady stream of water will run off. An even, intermittent sprinkling is best for deep penetration.
3. Soil Type — Coarse, sandy soil has large air spaces that quickly fill with water but also lose water quickly to the subsoil requiring shorter, more frequent watering. Heavier clay or silt soil has numerous smaller spaces that absorb water slowly but hold more water than sandy soil. Clay soil should be watered slowly but less frequently. Loam-type soil falls in between, holding water longer than sandy soil but not as long as heavy clay soils.
Let the soil dry between watering. Roots will grow deeper, looking for water below the surface as soil dries. Roots need to absorb small amounts of oxygen from air spaces in dry soil and are warmed by the drying soil. This also discourages weeds, which are often shallow-rooted.
Light watering produces shallow roots in the upper few inches of soil that are subject to rapid drying. In addition, many weeds have shallow roots that thrive on moisture near the surface. Too-frequent watering produces wet areas susceptible to lawn diseases, insects and drown root damage.
Most lawns need 1 to 2 inches of water per week depending on water and soil conditions. Nature supplies water as rain or dew but sometimes doesn't supply what's needed. In dry areas, a regular watering of at least once a week or more is important (skipping days when it has rained heavily). During the more moderate spring and fall or in cooler, wetter regions, look for signs that watering is needed. A slowing of the growth rate, changes in color or loss of resilience (footprints showing in the grass) are signs water is needed. Check the soil 2 to 6 inches below the surface. If the soil is dry and crumbles easily, it's time to water.
Time of Day
If nature hasn't supplied water as rain, apply approximately 1 inch of water, (a general rule of thumb). This will give deep penetration of the soil to a depth of 6 to 8 inches. One inch of water or rain is equivalent to 623 gallons per 1,000 square feet. Water should be applied no faster than the soil is able to absorb it. If water begins to run off before 1 inch is applied, stop sprinkling until it's absorbed and then resume.
How long will applying 1 inch of water take? This depends on the size of the hose, pressure and type of sprinkler being used. There are several methods for determining how much you’re applying.
1. Do the Math — Find the gallons per minute (GPM) flow rate of the sprinkler being used from the package of the manufacturer. Multiply the square footage to be watered by .62 gallons or 1 inch of water per square foot. Example: 1,000 square feet x .62 gallons = 620 gallons. This tells you how many gallons of water you need to apply to the lawn. Divide that number by the GPM of your sprinkler, and you can figure how many minutes to water.
2. Collect the Water — Place a cup or glass in the middle of the area covered by your sprinkler, turn water on and watch the time. Measure water in the cup until 1 inch is collected. This is the time you need to sprinkle. The best accuracy is obtained if you use several containers at different places in the sprinkler’s coverage pattern and average the results.
3. Buy a Flow Timer — Often called water timers, these units actually measure water flow. They are calibrated in 100 gallons and can be set from 100 to 1,500 gallons to give you the water necessary for the square footage covered by the sprinkler. Use the formula in Step 1 to calculate the gallons needed.
4. Test the Soil — Test the soil 6 inches or more below the surface to make sure it's dry. Turn on your sprinkler, and periodically test the soil 6 inches down until the water has penetrated to that depth. Keep track of how long it took, and use that as the time you need to water.