Specs are compiled from manufacturer listings and verified buyer reviews and can change over time — please confirm the key details on the product page before buying.
St. Augustine grass is a hungry, picky lawn, and getting the nitrogen balance wrong usually means scorched blades or a patchy mess. The 16-4-8 ratio hits the balance for this turf type, delivering steady green-up without the excessive growth that invites pests like chinch bugs. This guide compares the leading granular and liquid options in this exact ratio, so you can match the right format to your spreader, your schedule, and how fast you want results.
I’m Rikta — the founder and writer behind Lawn Gear Lab. This guide is built by comparing the manufacturers’ published specifications and the patterns across verified customer reviews, so you get each pick’s real strengths and trade-offs instead of marketing spin.
If you want a lawn that turns a deeper shade of green within a week without the guesswork, the best 16-4-8 fertilizer for St. Augustine grass depends on granule fineness and nitrogen release speed.
Our Picks at a Glance
How To Choose The Best 16-4-8 Fertilizer For St. Augustine Grass
St. Augustine is a coarse, fast-spreading turf that needs steady nitrogen, a decent dose of potassium for heat tolerance, and very little phosphorus in most soils. A 16-4-8 blend gives you exactly that: 16% nitrogen for color and growth, 4% phosphorus for rooting, and 8% potassium for stress resistance. The real buying decision depends on format, release speed, and how the product actually behaves in your spreader.
Granular vs. Liquid: Which fits your routine?
Granular formulas are the classic choice for large St. Augustine lawns — you fill a broadcast spreader, walk the yard, and let rain or irrigation carry the nutrients down to the roots. Liquids win when you want speed and precision, letting you spray exactly where the grass needs help, though they often demand a hose-end or pump sprayer you may need to buy separately.
Nitrogen release: fast, slow, or both?
Quick-release nitrogen greens a lawn within days but fades fast and can burn if you overdo it. Slow-release nitrogen feeds steadily over weeks, keeping the color even but taking longer to show. The strongest products blend both, giving you an immediate visible response and a longer feeding window in a single application.
Quick Comparison
| Model | Best For | Format | Weight | Coverage | Amazon |
|---|---|---|---|---|---|
| The Andersons PGF★ Best Overall | Best Overall | Granules | 18 lb | 5,000 sq ft | Amazon |
| Simple Lawn SolutionsBest Liquid Value | Best Liquid Value | Liquid | 2 lb | — | Amazon |
| Prevegenics | Quick Trial Size | Liquid | 2 lb | 10,000 sq ft | Amazon |
| PROXIO | Largest Granular Bag | Granules | 40 lb | 11,000 sq ft | Amazon |
| LawnStar | Premium Liquid | Liquid | — | 16,000 sq ft | Amazon |
| PetraMax | Largest Coverage | Liquid | 9 lb | 25,600 sq ft | Amazon |
In-Depth Reviews
1. The Andersons Professional PGF Complete 16-4-8 Fertilizer
Our pick — over 4.5★ from 3,500+ verified ratings; the strongest balance of quality and price.
The lawn-care equivalent of a professional-grade secret, this granular feeds for weeks and greens in days.
The defining trait here is the particle size — you won’t see the green striping or yellow gaps that coarser blends leave behind. For St. Augustine, even coverage matters because patchy feeding shows up fast as uneven color.
The nitrogen is split between quick- and slow-release, so you get an immediate visible response and continued feeding for up to 8 weeks from one application. Buyers report a noticeable darker green within a week, and some saw bare patches fill in over about a month and a half — the kind of recovery story that explains why this bag has become a crowd favorite.
It’s phosphorus-free, which is a genuine plus if your soil test already shows adequate phosphorus, and the 7% Humic DG works on the soil itself, improving nutrient uptake rather than just dumping food on top. At 18 pounds, it’s not the cheapest per-pound granular here, but the coverage and the results justify the premium for most homeowners.
Why owners stay loyal
- Fine particles spread evenly, cutting down on stripes and missed spots
- Blended release feeds for up to 8 weeks
- Humic DG improves soil condition, not just grass color
- Reports of dramatic green-up within a week
What to weigh first
- One bag covers 5,000 sq ft, so larger lawns need a second order
- Some find the per-bag cost higher than basic granulars
Reach for this if: you want professional-grade results from a granular that handles both the fast green-up and the long feed.
A fair heads-up: check your yard’s square footage before ordering — a bigger lawn means multiple bags.
2. Simple Lawn Solutions Advanced 16-4-8 Balanced NPK
A concentrated liquid that brings a neglected lawn back to life, one hose-end sprayer pass at a time.
This 32-ounce concentrate is built around a pure 16-4-8 NPK base that’s boosted with seaweed and fish emulsion, adding organic matter to the soil for better nutrient uptake. The mix ratio is straightforward — 3 to 5 fluid ounces per gallon of water — making it forgiving for first-time liquid users.
The biggest selling point is the visible speed. Owners describe grass turning noticeably greener and thicker after about a week and a half, with some seeing results in under a week on lawns that had been neglected through drought and heat. The liquid format lets you target thin patches directly, which granulars can’t do as precisely.
It’s explicitly labeled for all grass types, naming St. Augustine right alongside Bermuda, Zoysia, and Centipede, so you aren’t gambling on compatibility with your turf. A 2-pound bottle concentrates a lot of feeding power, though heavy feeding on a lawn in bad shape means you’ll go through it faster than you might expect.
The honest trade-off: this is a maintenance-grade feed that shines on lawns already on the mend; if your St. Augustine is severely yellowed, you may need more than one bottle to see a lasting change.
Who it beats: homeowners who want liquid speed without a premium price tag, applied through a hose-end sprayer in minutes.
Who it doesn’t: those expecting a single small bottle to rescue a season of neglect.
3. Prevegenics 16-4-8 Liquid Lawn Fertilizer
A 32-ounce tester that tells you fast whether liquid feeding fits your St. Augustine routine.
The value here is in the low commitment — a 32-fluid-ounce bottle that covers up to 10,000 square feet, which is enough to trial the liquid method on a decent-sized yard before you invest in bigger jugs. It’s a balanced 16-4-8 with added iron and L-amino acids, ingredients aimed squarely at deepening color and supporting root strength.
The mixing ratio is a simple 3 to 5 fluid ounces per gallon of water, and the results can be quick — one owner sprayed at the recommended rate and saw visible change in 3 days. That’s the kind of turnaround that makes liquid fans out of granular loyalists.
A couple of practical notes: the bottle’s pour cap doesn’t measure out the stated ounce amounts cleanly, so a separate measuring cup makes dosing easier, and the 2-pound weight means you’re paying for a concentrated, not a heavy dilute mix.
Best used as: a seasonal booster or a first-timer’s introduction to liquid 16-4-8 feeding, especially on St. Augustine that needs a fast color lift.
Grab it for: spot-treating thin or yellow patches without committing to a full lawn program.
Keep in mind: you’ll need a sprayer and a measuring cup for the cleanest application.
4. PROXIO 16-4-8 Lawn Fertilizer with Humates
The 40-pound sack for homeowners whose St. Augustine runs into the thousands of square feet.
Coverage is the whole story here — a 40-pound bag of ultra-fine granules that treats up to 11,000 square feet, which puts it in a different league from the 18-pound competitor. For a large St. Augustine yard, that means one bag instead of three, and fewer trips to the spreader.
The formula combines quick- and slow-release nitrogen for up to 8 weeks of feeding, and it includes organic Humic DG to enrich the soil and support stronger root growth. The fine granules are designed to work with most spreaders, giving even distribution without the clumping that plagues cheaper blends.
Feedback is genuinely mixed on arrival condition — some bags have shown up wet and clumpy, a shipping risk that’s hard to predict. Most users report healthy, happy lawns, and repeat buyers use it year after year, but the moisture issue is worth knowing before you order.
What wins here: the sheer square-foot coverage per bag, matched with a sensible 16-4-8 ratio and humate soil benefits.
Best for: large St. Augustine lawns where bag count and per-square-foot cost matter most.
Think twice if: you’re sensitive to the occasional clumpy delivery — inspect on arrival.
5. LawnStar Premium 16-4-8 Nutrient Liquid Fertilizer
A gallon of premium liquid that outpaces a commercial lawn service for a fraction of the hassle.
This is the liquid for owners who want rapid results and don’t mind a premium product. The 128-fluid-ounce jug combines fast- and slow-release nitrogen sources for quick greening plus longevity, and adds highly-bioavailable seaweed extract for maximum effect — all in a formula that treats up to 16,000 square feet.
The 1:10 mix ratio keeps it simple, and it’s compatible with any hose-end or garden sprayer. Owners mention visible results within 48 hours, with lawns looking healthier than they did under a paid commercial service — a strong claim that shows up repeatedly in the feedback.
The catch is real and consistent: this product carries sediment, and it can clog sprayer filters if you don’t clean them regularly. It’s a manageable quirk — shaking well and checking filters handles most of it — but it’s not a grab-and-spray product.
The speed is real: 48-hour results reported by multiple owners, with a 30-day no-questions-asked guarantee backing the purchase.
Choose this when: you want the fastest possible liquid response and you’re comfortable maintaining your sprayer’s filter.
skip it if: you’d rather not fuss with sediment and clogging during application.
6. PetraMax Liquid Lawn Fertilizer 16-4-8
A gallon of liquid feed with an absurd coverage ceiling — 25,600 square feet from one jug.
No other product in this lineup matches the raw coverage of this PetraTools concentrate. Mix 5 ounces per gallon for maintenance feeding, or double it to 10 ounces per gallon to correct deficiency, and you can treat up to 25,600 square feet at the maintenance rate — enough for the largest residential St. Augustine lawns on the market.
The formula is a 2-in-1 nitrogen system: quick-release nitrogen for the immediate green-up, slow-release for continued growth between applications. It also packs high-purity humates and extra potassium to encourage deep root development, which is exactly what St. Augustine needs during summer heat.
The recommended cadence is an application every 14 days, which makes this jug the economical choice for a big lawn over a full season. One sprayer-related clog report exists, but most customers note smooth application with no filter issues after a good shake.
The standout: 25,600 sq ft coverage versus 16,000 sq ft for the next-largest liquid, at a per-square-foot cost that’s tough to top for continuous feeding.
Made for: owners of very large St. Augustine lawns who want a liquid feeding program that stretches a single gallon across the whole yard.
Know before you buy: this is a 9-pound jug of concentrate — plan for storage and a proper sprayer.
Understanding the Specs
N-P-K Ratio (16-4-8)
The three numbers tell you the percentage of nitrogen, phosphorus, and potassium in the bag. The 16% nitrogen drives the green color and blade growth St. Augustine craves; the 4% phosphorus supports root development; the 8% potassium builds tolerance to heat and drought. The 4-1-2 relationship between them is what makes this ratio a safe, balanced choice for warm-season turf.
Release Speed
Quick-release nitrogen shows color within days but fades fast and can burn. Slow-release nitrogen feeds steadily for weeks but takes longer to show. Products that blend both, like the top granular and several liquids here, give you the instant satisfaction and the extended feeding in one pass — the best of both worlds for a busy homeowner.
FAQ
Is 16-4-8 the right ratio for St. Augustine grass?
How often should I apply 16-4-8 fertilizer to St. Augustine?
Granular or liquid 16-4-8 for St. Augustine — which is better?
Will 16-4-8 fertilizer burn my St. Augustine grass?
How much area does a 16-4-8 bag or bottle cover?
What is Humic DG and why does it matter for St. Augustine?
Can I use 16-4-8 on other grass types like Bermuda or Zoysia?
Why is my liquid 16-4-8 clogging my sprayer?
When is the best time of year to apply 16-4-8 to St. Augustine?
Do I need a spreader for granular 16-4-8, and will it work with mine?
Final Thoughts: The Verdict
Across the board, the 16-4-8 fertilizer for st. augustine grass winner is the The Andersons PGF Complete because it combines fine-particle even coverage, a 4-1-2 ratio, and up to 8 weeks of slow-release feeding with fast visible results. If you want liquid speed and the convenience of a hose-end sprayer, grab the Simple Lawn Solutions 16-4-8. And for a very large St. Augustine lawn where one jug needs to go the distance, the PetraMax delivers class-leading coverage per gallon.
How We Picked
We do not accept paid placement. Every pick is matched to a real buyer and a real use-case; we do not hands-on test units.
Sources & Methodology
Specifications: manufacturer listings and product documentation. Review insights: verified customer reviews, as of August 2026. Pricing: not shown on this page (it changes often); check the current price via the retailer link.
As an Amazon Associate, Lawn Gear Lab earns from qualifying purchases. This does not affect which products we feature.