If your lawn is turning yellow even though you're watering consistently, you're almost certainly dealing with iron chlorosis — a condition caused by Fresno's naturally alkaline soil (pH 8.0+) that prevents grass from absorbing iron. It's the #1 lawn problem we see across Kerman, Fresno, and Clovis, and it's fixable.
What Is Iron Chlorosis?
Iron chlorosis is a nutrient deficiency where grass cannot absorb iron from the soil, even though iron is present. The problem isn't a lack of iron — it's that Central Valley soil pH is too high (alkaline) for the iron to dissolve into a form plant roots can use. At pH 8.0 and above, iron locks into insoluble compounds in the soil.
How to identify it:
- Grass blades turn yellow or yellowish-green
- Leaf veins often stay darker green while the tissue between veins turns yellow (interveinal chlorosis)
- Newer growth is affected first (youngest blades show it before older ones)
- The lawn looks washed out, pale, or lime-green despite regular watering
- The problem is usually worst in areas with compacted or poorly draining soil
What it's NOT: Iron chlorosis looks different from drought stress (which causes wilting and browning from the tips) or nitrogen deficiency (which causes uniform pale green across the entire blade, starting with older growth).
Why Does This Happen in Fresno?
Fresno, Kerman, and Clovis sit on San Joaquin series soil that naturally runs pH 7.5–8.5 — significantly alkaline. Here's why that matters:
- At pH 7.0 (neutral), iron is moderately available to plants
- At pH 8.0+, iron becomes almost entirely insoluble
- Central Valley soil is also heavy in calcium carbonate, which further locks out iron
- Clay-heavy soil compacts easily, reducing root access to what little available iron exists
- Overwatering raises soil pH even further by leaching acidic elements out of the root zone
This isn't a problem homeowners are causing — it's built into the geology of the Central Valley. But it is manageable with the right approach.
How Do I Fix Yellow Grass From Iron Chlorosis?
There are three approaches, ranked from quickest fix to longest-lasting solution:
Quick Fix: Foliar Iron Spray (Works in 3–7 Days)
Spray ferrous sulfate (iron sulfate) directly onto grass blades. The grass absorbs iron through the leaves, bypassing the soil chemistry problem entirely.
- Application: 2–3 oz of ferrous sulfate per gallon of water, sprayed per 1,000 sq ft
- When: Early morning or late evening to avoid burn
- Results: Green-up visible in 3–7 days
- Duration: 2–4 weeks before reapplication needed
This is a temporary fix — you're treating the symptom, not the cause. But it works fast and buys you time to address the soil.
Medium-Term Fix: Chelated Iron (Lasts 4–8 Weeks)
Apply chelated iron with EDDHA or EDDHMA chelating agents to the soil. These chelates keep iron in a plant-available form even at high pH. Regular chelated iron (EDTA) breaks down in alkaline soil — you specifically need EDDHA for Fresno conditions.
- Application: Follow product label rates (typically 4–6 oz per 1,000 sq ft)
- When: Spring and early summer when grass is actively growing
- Results: Visible improvement in 1–2 weeks
- Duration: 4–8 weeks per application
- Cost: $15–$30 per application for a typical yard
Long-Term Fix: Lower Your Soil pH
To permanently address iron chlorosis, you need to bring your soil pH closer to 6.5–7.0. This takes time and consistent effort:
- Elemental sulfur: Apply 5–10 lbs per 1,000 sq ft in spring and fall. Soil bacteria convert sulfur to sulfuric acid, slowly lowering pH. Takes 3–12 months to show results.
- Sulfur-coated fertilizer: Use fertilizers with sulfur or ammonium sulfate as the nitrogen source instead of urea or ammonium nitrate.
- Compost and organic matter: Work 1–2 inches of compost into the soil annually. Organic matter naturally buffers soil toward neutral pH.
- Core aeration: Aerate in spring or fall to break up compacted clay and improve root access. This is especially important in our heavy clay soil.
Important note: Gypsum (calcium sulfate) is often recommended for clay soil, but it does NOT lower pH. Gypsum improves clay structure and drainage, which helps indirectly, but you need elemental sulfur to actually change pH.
How Do I Prevent Iron Chlorosis?
Once you've treated the immediate problem, these ongoing practices keep it from coming back:
- Water deeply but less frequently — overwatering raises soil pH. In Fresno's summer schedule, make your 3 watering days count with deep soaking rather than light sprinkles.
- Avoid over-liming — never add lime to Central Valley soil. Our soil is already too alkaline.
- Choose iron-efficient grass varieties — Bermuda grass tolerates alkaline soil better than fescue. If you're starting a new lawn, this matters.
- Fertilize with acidifying fertilizers — ammonium sulfate (21-0-0) provides nitrogen while gently lowering soil pH.
- Aerate annually — core aeration improves drainage and reduces compaction in our clay soil.
- Test your soil — a basic soil test ($15–$30 at Alluvial Soil Lab in Fresno) tells you exactly where your pH stands and what amendments you need.
When Should I Call a Professional?
If your lawn is severely chlorotic (more yellow than green), patchy, or not responding to iron treatments, it's worth having a professional assess the situation. The problem may be compounded by compacted soil, drainage issues, sprinkler coverage gaps, or pest damage.
Our lawn care maintenance plans include seasonal iron treatments and fertilization programs tailored to Central Valley alkaline soil. We also offer one-time soil assessments and treatment plans.
Book a service or call us at (559) 809-1230 for a free estimate. We serve Kerman, Fresno, Clovis, and surrounding areas.