A tailored sprinkler schedule promotes a resilient landscape while conserving water. The goal is to develop a routine that matches your specific lawn and environment, ensuring that water reaches the plant roots effectively. Achieving an efficient watering pattern requires understanding not just how often to run the system, but also for how long, and how to adjust the schedule throughout the year. This approach prevents water waste and encourages a healthier, more robust lawn.
The Fundamental Principle: Deep and Infrequent Watering
The basis of any effective irrigation schedule is the principle of deep and infrequent watering. Frequent, shallow applications of water keep the soil surface constantly moist, which encourages turf roots to stay near the surface. These shallow root systems make the grass vulnerable to heat stress, disease, and drought conditions.
In contrast, deep watering involves applying enough water to moisten the soil to a depth of six to eight inches, the typical root zone for established turf. Allowing the soil to partially dry out between watering sessions forces the roots to grow downward in search of moisture. This results in a deeper, more extensive root system that better withstands environmental stresses, leading to a healthier and more drought-tolerant lawn.
Key Factors Determining Your Sprinkler Schedule
The ideal watering frequency depends on local conditions, particularly your soil type. Soil texture dictates both the water-holding capacity and the infiltration rate (how fast the soil can absorb water). Sandy soil, characterized by large particles, drains quickly and has a low water-holding capacity. This soil type requires more frequent, yet shorter, watering cycles to ensure the roots get enough moisture before it drains away.
Clay soil, with its tiny, tightly packed particles, retains water for a longer period but absorbs it very slowly. For clay, water less frequently but for a longer total duration to allow the water to penetrate the dense structure. Watering too quickly on clay soil often results in pooling and runoff because the soil cannot absorb the water fast enough.
Plant type also affects frequency. Cool-season grasses, such as Fescue, actively grow in spring and fall, often requiring more water during these times. Warm-season grasses, like Bermuda, are dormant during cooler months and have their highest water demand during peak summer heat.
Local climate, measured by evapotranspiration (ET), is the third major variable, representing the rate at which water is lost from the soil and plants. High temperatures, strong winds, and low humidity all increase the ET rate, causing the soil to dry out faster. Monitoring these weather patterns is crucial for adjusting the time between watering days.
Practical Implementation: Setting the Watering Duration
Once the frequency is determined, the next step is calculating the duration of each watering session. The common target is to apply about one inch of water per week for established turf during the growing season, spread over one or two deep waterings. To find out how long your system needs to run, you can use the “catch can” test. This involves placing several straight-sided containers, like tuna cans, throughout a sprinkler zone and running the system for a set time, such as 15 minutes.
After the test, measure the average depth of water collected in the cans. Use a simple calculation to determine the total run time needed to apply one inch of water. For example, if you collected half an inch of water in 15 minutes, you need to run that zone for 30 minutes to apply one full inch. This technique accounts for the unique flow rate and efficiency of your specific sprinkler heads.
In areas with clay soil or significant slope, the total duration must be split using the cycle and soak technique to prevent runoff. This method divides the total watering time into multiple shorter segments, separated by a soak period. For instance, a 30-minute total run time could be split into three 10-minute cycles, with a 30- to 60-minute break between each cycle. The soak period allows the water from the first cycle to fully infiltrate the soil, preparing the ground to absorb the next application more efficiently.
Seasonal and Weather Adjustments
A static sprinkler schedule is inefficient, as water needs fluctuate dramatically with the seasons. During spring and fall, when temperatures are cooler and plant growth slows, reduce the watering frequency. A reduction of 10% to 30% from the summer schedule is often appropriate, or watering only once every week or two.
In the peak of summer, when heat and evaporation rates are highest, you may need to slightly increase the frequency of deep watering sessions. The duration of the cycle should remain the same, as the goal is still to reach the deep root zone. The best time to water is in the early morning, between 4 a.m. and 8 a.m., to minimize water loss to evaporation and allow the foliage to dry before nightfall, reducing the risk of fungal disease.
After significant rainfall, the system should be manually paused or automatically bypassed using a rain sensor to prevent over-saturation. Modern controllers often have a seasonal adjust feature that allows you to change the run time of all zones simultaneously by a percentage, simplifying these modifications.