Anything Cleaner/Organic for Phosphorus than Rock Phosphate? & Solve light-green lawn slow growth?


LawnSite Bronze Member
Soil tested Phosphorus = zero.

Is there anything cleaner/safer for environment than Rock Phosphate to boost levels when P tests at zero?

It's very costly though, $60 shipped for 50lbs only covers 1,000 sq ft, therefore a 8,000 sq ft lawn would need $480 of product!?

And the phosphorus number is only 3.
It says it should last up to 5 years though, and I'll mainly be using milorganite every 6-8 weeks which does supply some phosphorus, actually milo is 6-4-0 = more Phosphorus than this product?

This one 0-5-0 $87 shipped 50lbs only covers 2,000 sq ft. An 8K sq ft lawn would need $348 cost of product. is a,supplied continuously during that time.

Again though I am looking for cleanest form, and maybe this is do-able if it'll last 5 years and levels can be sustained after with organic milo and Purely Organic as mentioned later.

This tiny 4lb bag says 'covers 50 ft', $17 would still probably costs hundreds just for a small lawn, even though it's 0-18-0

Same with 0-45-0 $20 4lb bag
Does say rock phosphate but enhanced with chemicals, and I want the cleanest form.


Besides clean phosphorus supplementation, I have questions as to why the lawn is still slow growing and light green basically since last Fall's overseeding.

I used Titan Rx tall fescue but before you blame the seed (which ranks good in NTEP and isn't a bad cultivar) it was only an overseeding and the existing tall fescue makes up %80 of the turf is not as dark nor growing very vigorously (even before the heat waves hit), no sprinklers have been used but have been getting decent amounts of rain. Soil composition is good, not too clay or sandy.

The past few years I've been using about half synthetic, half milorganite on it. Synthetic Scotts starter (high in P) in Fall with overseeding (various brands pennighton, Rebel, Scotts etc, box store Tall Fescue seed) with core aeration. And used Scotts Winterguard (has some K) in Fall once or twice.

Before this, Scotts or true green was fertilizing it with all synthetics and it looked better and grew more vigorously. (I don't want to simply push top growth with synthetic nitrogen + liquid/granular Iron though).

I have Ironite too but not sure if that's the problem.

Milo is supposed to provide a decent amount of Iron, but the lawn is no where near as green as a neighboring one that just uses big box store synthetic, or ones likely being sprayed with liquid nitrogen + iron. They're all tall fescue lawns, not kentucky blue which is often darker. I soil tested one of those darker lawns and P and K were also zero. I did mulch a ton of leaves into one of the darker lawns over the past few years but P and K still tested zero. All lawns are mulched %90+ of the time, no bagging.

I'm just using a Luster Leaf 1662 Professional soil test kit, not a main-in lab kit, but youtube confirms DIY kits are accurate for NPK + pH compared to their lab results.

I heard using synthetics (Starter and Winterguard and a couple apps of Stagreen 29-0-5) can nullify the use of organics, In other words, when you've been using organic like milorganite and then use synthetic, it basically deletes the organics you've been using? Could that be why Phosphorus tested zero, or maybe that I took the sample about 5 weeks after applying the milo and it's due for another app?

(K) Potassium = was also totally depleted, a couple weeks ago I added Southern AG Sulfate of Potash which is or is probably the cleanest (and costliest) potash fertilizer aside from maybe wood ash which I doubt increases potassium as much, isn't practical, and could raise pH too alkaline.
Though I am considering adding lime could make it darker and more vigorous. pH tested around 6 neutral. But I'm not sure because a quick Google says Turf Type Tall Fescue thrives at 5.8 - 6.5. But just searching best pH for lawn is 6.5 - 7 ,but is likely skewed higher for kentucky blue preferring the higher pH.

The plan is to get the NPK + pH optimal using the cleanest organic products and then hoping those levels can be sustained by alternating milorgranite (6-4-0) and Purely Organic 10-0-2 every 6-8 weeks. And then in a few years if P and K dip too low re supplement them again, ideally in Fall/Spring and not now when lawn is almost dormant in some areas.

Purely Organic $25 for 5K sq ft is low cost, can get ship to store free pick up:

Milo is pretty low costtoo for an organic, not as cheap as synthetic but worth it for the organic IMHO, but what I'm not getting is how synthetics appear to be beating the organic, this can't happen, organic is supposed to be a win win = cleaner & better results.

Please if anyone has some info on this?, I'm not looking for 'have a lab do the soil test' (I mean what's it even going to tell me that some small trace mineral like magnesium or calcium is causing slow growth and lime green color?) or 'have a local fertilizing company look at it' (which likely wouldn't even use organics anyway).

thank you


LawnSite Bronze Member
good point, topdress compost should boost P and K, but depends on the source. would like to do a soil test before and after to see, but compost isn't very practical either though. Would only add it in Fall after core aerating, and want something to supplement and really boost depleted P and K levels.


LawnSite Fanatic
Grand Rapids MI
If you have been applying Milorganite, your phosphorus should be good--not zero.
Maybe the reagents in the test you have are too old. Sat in the store too long.
I suggest a full soil test with micronutrients--iron, manganese, copper, zinc, magnesium and so forth.
I am sure Phasthound can suggest an organic-oriented soil test in New Jersey--will check for organic levels, normal soil bacteria levels, fungi and certain other problems.


LawnSite Bronze Member
I don't want compost though... Just the cleanest form of Phosphorus to boost it from being zero. Would prefer no crushed up animal bones/fethers too.

Yes it could be the soil doesn't hold nutrients as well (yes compost after aeration would greatly help that though, but just brainstorming now), and the test was taken about 6 weeks after applying milorganite could be why.

I can get Oceangro too in NJ, cheaper than milo, same thing basically except a tad more phosphorus (6-4-0 VS 5-5-0). Didn't want to confuse any further by mentioning OG.

milo/OceanGro phosphorus %s are the same as the pricey Rock Phosphate?!

Aside from that riddle about dark green lawn , pH, vigor, etc, I'm just asking the cleanest form of phosphorus now.

If it's ~$348 for a 8,000 sq ft lawn, BUT lasts up to 5 years, and should be sustained thereafter with milorganite/OG, then $70 a year for Rock Phosphate is sort of do-able for 8,000 sq ft, I would probably skimp a bit on it too to lower cost, I want the safest/cleanest option overall.

Sulfate of Potash costs like $80 per 8K or something and I already used that, and might not last many years (hoping alternating Purely Organic Lawn Food 10-0-2 with Milo/OG apps will help though).

BTW even if it's $70 a year, that's a better price and labor than spreading compost, which has to be timed in Fall otherwise hello crabgrass infestation or Drive XLR8 which I want to avoid, same with PreEm.

It would be good to get an analysis of compost but might not be practical. I used 7 yards today, I could tell/smell it was like half horse manure (finished), thus high in Nitrogen but "less than %1 phosphorus", and the rest is probably leaves and grass also not really high in phosphorus.

The lawn is at least alive and not even dormant without irrigation right now, maybe if I just stop all synthetic apps forever and alternate Oceangro and Purely Organic Lawn Food it'll darken, and grow more vigorously (plus irrigation in Summer and stay cutting on the highest height), add some Ironite now and then to really darken it if the Iron in Milo/OG isn't enough.


which has to be timed in Fall otherwise hello crabgrass infestation
This is wrong. You can use compost any time of the growing season. No need to core before either.

could tell/smell it was like half horse manure (finished), thus high in Nitrogen but "less than %1 phosphorus", and the rest is probably leaves and grass also not really high in phosphorus.
Sounds well smells like you don't have good finished compost. It should have a earthy smell. Not a manure smell. I would find a better supplier.

FYI there is a lot more to growing great grass then NPK. Don't get too focused on those numbers. Oh and compost is the answer to almost any question in "Organic" lawn care. Embrace it, use it, love it.


LawnSite Fanatic
Grand Rapids MI
Your plan is good. I think horse manure should work for your situation--if combined with steady irrigation. Correct acid soil--if any.
I hope it works--get pictures, OK?
The typical analysis is, 0.7-.3-.6. The manure contains lots of beneficial organic matter and undigested roughage. If you applied four times as much as an ordinary lawn fert you would have about 28-12-24. It is not low in phosphorus, in fact, rather high, compared to most lawn fertilizers, (like Lesco 24-0-11, for instance).

On the other hand the Ocean-gro processed sewage residue you mentioned should work for your situation, about half as much phosphorus as nitrogen.
Then you need potassium. Shop around you should be able to find potassium sulfate for less. If not use potassium as muriate of potash. You should get it for about $12 per 50 pound bag, 0-0-62. Treats about 62 thousand sqft.
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