A weak lawn eventually becomes a weedy lawn. Incorrect watering is one of the things that weaken turfgrasses and allow weeds to invade. Greenside Landscaping lists some poor irrigation practices that often complicate lawn weed control in Utah.
Light, frequent irrigation
Deep, infrequent watering of established turfgrass leads to healthy root growth. Conversely, light, frequent irrigation encourages shallow root growth. And a shallow-rooted yard is less durable and susceptible to invasions by crabgrass and other weeds. Irrigation management experts recommend watering up to a depth of about 6 to 8 inches, and irrigating again after 1 to 2 inches of topsoil have dried out.
Poor irrigation application uniformity
Uneven coverage often leads to dry or dead spots that encourage weed growth. Make sure your sprinkler heads are not broken or obstructed and set the sprinklers appropriately so that they may reach all areas of your lawn.
Failure to consider the soil type
You should consider your soil and water accordingly. Sandy soils allow quicker drainage and drying out than clay soils and therefore need more frequent watering. Remember to water turfgrass on clay soil in a way that will enable water infiltration without puddling and runoff.
Disregard of the climate, turfgrass species, and growing conditions
Lawn irrigation needs vary among plant species. Water requirements should also vary depending on the time of year, climate and growing conditions. Consider all these factors to prevent over-watering or under-watering that may encourage weeds. If you have warm season grasses, water your lawn once or twice each week. If you have cool-season grasses, water the turfgrass thrice a week if the weather is hot. You should water less frequently if your lawn is under shade.
Weeds often invade lawns that are under-watered, over-watered, improperly fertilized or improperly mowed. Your lawn is also likely to become weedy if pests and diseases weaken it. Keep your turfgrass healthy to win against stubborn weeds.