# How to Calibrate Your Irrigation System for Middle Tennessee's Challenging Soils If you've ever wondered why your sprinkler system seems to work great in some areas of your lawn but leaves other spots bone dry or soggy, you're not alone. Here in Middle Tennessee, we deal with something that makes irrigation tricky: what I call "suburban soils." After working on lawns throughout Columbia, Franklin, and Spring Hill for over a decade, I've seen this problem countless times. Let me explain what's happening and how to fix it. ## The Middle Tennessee Soil Challenge When developers build new neighborhoods around here, they often scrape away the good topsoil and leave behind compacted subsoil. This "suburban soil" creates all kinds of drainage headaches that your irrigation system wasn't designed to handle. I learned this the hard way about 12 years ago when I was trying to figure out why a customer's lawn in a newer Franklin subdivision had such uneven growth. Half the yard was lush and green, while the other half looked stressed despite having the same sprinkler coverage. Turns out, the compacted subsoil was causing water to run off instead of soaking in. The sprinklers were putting out the right amount of water, but the soil couldn't absorb it fast enough. ## Why Standard Irrigation Settings Don't Work Most irrigation systems are set up with the assumption that your soil can absorb water at a reasonable rate. But compacted suburban soils often can't keep up with even a moderate sprinkler output. Here's what typically happens: your sprinklers start running, the first few minutes soak in fine, but then the soil reaches its absorption limit. The rest of the water just runs off into the street or pools in low spots. Meanwhile, your irrigation controller thinks it's delivered the right amount of water, but your grass roots never got most of it. ## The Catch Can Test: Your Starting Point Before you can fix your irrigation timing, you need to know exactly how much water your system is putting out. This is called a "catch can test," and it's easier than it sounds. **What you'll need:** - 6-10 straight-sided containers (empty cat food cans work great) - A measuring cup or ruler - A calculator - About 30 minutes **Here's how to do it:** **Step 1:** Place the containers randomly throughout one sprinkler zone. Don't line them up in a row - scatter them around to get a good average. **Step 2:** Run that zone for exactly 15 minutes. **Step 3:** Collect all the containers and measure the water depth in each one. **Step 4:** Add up all the measurements and divide by the number of containers. This gives you your average application rate for 15 minutes. Let's say your average is 0.25 inches in 15 minutes. That means your system puts out 1 inch of water in 60 minutes (0.25 × 4 = 1.0). ## Understanding Your Soil Type This is where Middle Tennessee gets tricky. You might have different soil types in different parts of your yard, especially in newer developments. **Sandy soils** (rare around here, but they exist): Water soaks in quickly, but doesn't hold much. These areas need frequent, shorter watering - maybe 2-3 times per week. **Clay soils** (very common): Water soaks in slowly but holds well once it's there. These areas need less frequent but longer watering sessions. **Compacted subsoil** (the suburban soil problem): Water barely soaks in at all initially, but once you get it wet, it holds water reasonably well. ## The Cycle and Soak Solution This is the game-changer for Middle Tennessee lawns. Instead of running your sprinklers for one long session, you break it up into shorter cycles with breaks in between. Here's how it works: instead of watering for 30 minutes straight, you might water for 10 minutes, wait 30 minutes, then water for another 10 minutes, wait again, then finish with a final 10-minute cycle. This gives the compacted soil time to absorb each round of water before the next cycle starts. ## Setting Up Cycle and Soak Most modern irrigation controllers can handle this, though the setup varies by brand. Look for settings called "cycle and soak," "smart watering," or "multiple start times." **Basic setup example:** - Total water needed: 1 inch per week (typical for fescue in summer) - Your system output: 1 inch per hour (from your catch can test) - Soil type: Compacted clay (common in suburban developments) **Instead of:** 1 hour straight, twice per week **Try:** 20 minutes, 3 times with 30-minute breaks, twice per week The total water is the same, but now your soil has time to absorb it. ## Adjusting for Different Areas You might need different settings for different zones based on: **Slope:** Steeper areas need shorter cycles and longer soak times **Shade:** Shaded areas typically need less water overall **Soil compaction:** More compacted areas need more cycles with longer breaks **Grass type:** Fescue (most common here) needs deep, less frequent watering ## Testing Your Results After you've adjusted your irrigation timing, give it a few weeks and then check your results: **Good signs:** - Even green color across the entire zone - No runoff during watering cycles - Soil feels moist 4-6 inches deep the day after watering - No soggy or dry spots **Problem signs:** - Water running off during cycles (need shorter cycles or longer breaks) - Dry spots (might need more total water or better coverage) - Soggy areas (might be overwatering or have drainage issues) ## Seasonal Adjustments Middle Tennessee's weather changes throughout the year, so your irrigation needs will too: **Spring:** Reduce watering as rainfall increases and temperatures are moderate **Summer:** Peak watering season - your cycle and soak settings will get the most use **Fall:** Gradually reduce as temperatures drop and rainfall typically increases **Winter:** Most systems should be shut off, though you might need occasional watering during dry spells ## When Professional Help Makes Sense Sometimes the problem isn't just timing - it might be your sprinkler heads, water pressure, or system design. If you're still getting uneven coverage after adjusting your timing, consider having a professional irrigation audit. Signs you might need professional help: - Huge variations in your catch can test results - Persistent dry or soggy spots despite timing adjustments - Very low water pressure - Sprinkler heads that don't pop up properly ## The Bottom Line Calibrating your irrigation system for Middle Tennessee's challenging soils isn't just about following the manufacturer's recommendations. Our compacted suburban soils require a different approach - one that gives the soil time to absorb water instead of just dumping it all at once. The cycle and soak method has solved irrigation problems for countless homeowners I've worked with over the years. It takes a little time to set up and fine-tune, but the results are worth it: a more evenly watered lawn that uses water more efficiently. ## Need Professional Irrigation Management? If all this sounds more complicated than you want to deal with, that's exactly why professional lawn care services exist. At Mr. Lawn Care, we understand Middle Tennessee's unique soil challenges and can help optimize your irrigation system for maximum efficiency. We serve homeowners throughout Columbia, Franklin, Spring Hill, Brentwood, and the surrounding areas. Our team knows how to work with the challenging soils common in our newer developments and can help you get the most out of your irrigation investment. Give us a call at (615) 490-4082 or email aj@mrlawn.care. Sometimes the best irrigation calibration is having professionals who understand local conditions handle it for you. --- *Been troubleshooting irrigation issues in Middle Tennessee for over a decade. Every yard teaches me something new about working with our challenging soils. Got irrigation questions? Feel free to reach out.*