Your results are back. Unless you've spent your weekends in a soil lab, they probably look like alphabet soup. Here's what those numbers are saying about your yard (and how to handle them).
How Sunday uses your results
Every gap your lawn soil test reveals gets addressed in your plan. No guesswork on your end, no product research required. Sunday identifies what's actually missing and builds it into your shipments. What your lawn doesn't need stays out.
- If you bought a standalone soil test, your results include clear product recommendations you can act on directly.
- If you're on a Custom Lawn Plan, Sunday handles the adjustments automatically and will support you with expert lawn consultations.
How often should you retest? Every two to three years is enough. Soil chemistry moves slowly, and retesting again in early spring or fall give you the cleanest read on where things stand.
The foundation: pH, organic matter, and CEC
Soil pH
pH is the single most important chemical property in your soil. It controls which nutrients your grass can actually access. Even nutrient-rich soil can underperform if pH is too far off.
The standard textbook target is 6.5 to 7.0, but Sunday's data shows lawns thrive anywhere above 5.5. High pH above 7.0 is common in the western U.S. and rarely causes issues. Once pH climbs above 8.0 it starts locking nutrients in the ground. If your levels hit that point, Sunday will flag it and tell you what to do.
Sunday Tip:
At least 10% of Sunday customers fall below 5.5 with no visible problems, though we still monitor it to keep the grass resilient.
Organic matter (OM)
Organic matter is what keeps your soil alive and working. You want at least 2% in your results. It holds water, feeds the microbial life underneath, and keeps nutrients available between applications.
When OM drops, the biological activity in your soil slows down and the lawn starts leaning on products to make up the difference. Topdressing with compost can help build it back gradually, and the improvement shows up season after season.
Cation exchange capacity (CEC)
CEC measures how well your soil holds nutrients before they drain away. It's largely determined by your soil's texture, which means it doesn't shift much over time. Knowing it tells Sunday how to pace your nutrient applications.
Sandy soils have low CEC so nutrients move through quickly, which is why more frequent applications tend to work better. Clay soils grip nutrients tightly but often need help with drainage and aeration. Loam is the most forgiving of the three to manage.
Psst. What's a good soil test result? A healthy lawn doesn't need to hit every perfect number. Generally Sunday looks for pH between 5.5 and 7.0, organic matter at 2% or higher, and CEC between 8 and 20. If your numbers are outside that, that's exactly what your custom plan is built around.
What each nutrient in your soil test tells you
Nitrogen (N)
Nitrogen is the most important nutrient in your Sunday plan. It drives growth and helps grass fill in before weeds get the chance.
Nitrogen isn't on your results page because it changes week to week based on rainfall, temperature, and microbial activity. A single test captures a snapshot of a constantly shifting number, not a reliable picture.
Sunday applies nitrogen over the full season in steady, even amounts. Heavy doses push excessive top growth, increase mowing, and stress the grass without making it stronger.
Phosphorus (P)
Phosphorus is critical for new lawns. Seedlings need it to develop roots and establish their first real foothold in the soil. For mature lawns it's almost always already present because phosphorus binds tightly to soil particles and builds up over time. Most established lawns sit at or above the 21 ppm threshold Sunday looks for.
Adding more phosphorus to a lawn that doesn't need it doesn't help the grass. It moves off the lawn in runoff and ends up feeding algae blooms in local waterways. Sunday avoids phosphorus unless your test shows a genuine deficiency.
Potassium (K)
Potassium manages how your lawn handles heat, drought, and heavy use. It regulates the internal water pressure of the grass, helping it stay upright when conditions get stressful. Without enough potassium, grass can't move water internally, which is why deficient lawns wilt fast in summer heat.
Potassium is soluble and moves through soil easily, so coastal and rainy regions tend to see more deficiency than average. Adequate levels start at 37 ppm. Sunday includes potassium across most products in the plan.
Sunday Tip:
Fewer than 15% of customers are deficient in potassium, but if you are, a boost pouch is already built into your shipments.
Calcium (Ca)
Calcium is the structural nutrient. It builds cell walls, keeps the grass from going limp under pressure, and supports root tip development. Deficiency is genuinely rare because calcium is abundant in most soils.
Where it becomes relevant is pH: calcium carbonate is the primary ingredient in lime, which is how acidic soils can get be corrected over time. If your pH is low enough to matter, Sunday will flag it and liming your lawn is usually the recommended path.
Magnesium (Mg)
Magnesium is at the core of every chlorophyll molecule your grass produces. It's not something most lawns run short on. In fact, fewer than 2% of Sunday customers show a deficiency.
But when it does come up, the fix is straightforward: magnesium sulfate, already accounted for in your plan if the test calls for it.
Sulfur (S)
Sulfur is involved in protein synthesis and enzyme activity throughout the plant. The most visible sign of a deficiency is a lawn that stays pale or yellowish even after nitrogen has been applied. If the grass won't green up and nitrogen isn't the issue, sulfur or magnesium is usually worth looking at next.
About 5% of Sunday customers show a sulfur deficiency. Sunday delivers it in sulfate form, which is stable and safe at normal application rates.
Sunday Tip:
Straight elemental sulfur is a different product entirely. It can acidify soil quickly and burn turf in warm conditions. Sunday doesn't recommend it.
Iron (Fe)
Iron supports chlorophyll production, which is what drives the deep green color you're after every season. With this nutrient, you get earlier lawn green-up and richer color—without pushing excess nitrogen onto a lawn that isn't ready for it yet.
Sunday applies iron throughout the season in a form that plants absorb more readily. It's central to the first spring shipment for exactly this reason.
Sunday Tip: Iron has a quiet but powerful biological effect on certain lawn diseases and weed seedlings. The same compound in Dandelion Doom and Weed & Green shows up in most Sunday lawn fertilizers at a fraction of the concentration.
Micronutrients
Boron, manganese, copper, and zinc are needed in small amounts but they matter. They support enzyme function, disease resistance, and the color and structural health of your grass. Sunday's plans include them where your soil data shows a need.
What to do with your results
Your Sunday plan handles most of this automatically. But knowing what's happening helps you work with it.
Nitrogen shows up in your lawn's color and growth rate, not in your test results. Watch for pale or slow-growing grass mid-season. Your custom plan and Yard Advisors can adjust timing if something looks off.
Phosphorus, potassium, or sulfur deficiency gets addressed in your next shipment. Sunday adjusts automatically when your results show a shortfall. Nothing extra to order.
Low organic matter is a slower fix. Topdressing with compost once or twice a year builds it back over time and feeds the microbial life that keeps your soil working between applications.
Sandy soil (low CEC) loses nutrients faster, so more frequent, lighter applications keep the lawn fed without wasting product.
Clay soil (high CEC) holds nutrients well but benefits from regular aeration to keep roots from struggling with compaction.
pH out of range rarely needs a dramatic fix. If yours is low enough to matter, Sunday will flag it and lime is usually the path forward. Alkaline soil above 8.0 needs a different approach and Sunday will tell you if you're there.
Lawn soil test FAQ
What happens if my soil test shows a deficiency?
Sunday adjusts your plan automatically. If you're on a Custom Lawn Plan, the right products show up in your next shipment. If you bought a standalone test, your results come with clear recommendations you can act on directly.
Bought a soil test without a Custom Lawn Plan?
Your results will be emailed to you about four weeks after the lab receives your sample. They include product recommendations you can use right away, or you can add a Custom Lawn Plan and let Sunday build those adjustments into your shipments going forward.
