Reactive Phosphate Rock

[wigs]

Hi all,
I am looking at adding Reactive Phosphate Rock (1-2 cups) to my base soil as a amendment before I plant (40l container). Has anyone had any experience with this product for P?

Or would it be smarter to add this in later in the flowering stage? This will be an outdoor grow too.

Thanks

 

[benn0]

Foliar sprayable giving it fungicide qualities or can be added fertigated or poured straight on roots at the correct rate

 

[wigs]

Thanks for your feedback! So you wouldn't recommend adding it to the base soil profile at the start?

 

[benn0]

I dunno man im not into the organic stuff or the build a soil stuff I was just being funny, there plenty of other people here that will help you out soon

 

[med180]

Thanks for your feedback! So you wouldn't recommend adding it to the base soil profile at the start?

Wait for ichybro or vinD to chime in...
They're all over soil!

 

[Pikey]

Wait for @itchybro or vinD to chime in...
They're all over soil!

Fixed it for ya

 

[wigs]

Haha thanks @benn0 I appreciate your comment nonetheless!

Cheers @Pikey and @med180 - I have actually been following @itchybro base soil mix.. Trying to give the organic run a red hot crack this summer!

 

[benn0]

I was expecting a reply from someone that is in the know much sooner but hopefully you don't have to wait days now

 

[itchybro]

G'Day guys

sorry @wigs , been busy mate , lots happening in life lately

I've never used Reactive Phosphate Rock myself so if i was to use it without doing a bit of research on it first , i would tend to use it as a top dress because top dressing anything can be allot more forgiving than adding it as a mixed soil amendment or using liquid fertilizers for that matter

I find the mix i use or the coots mix to be very much sufficient through a grow along with using top dressing worm castings , watering in or spraying Aloe , Coconut water , potassium silicate & EM-1 , most importantly the quantity of soil used , 50 liter is an absolute minimum & getting your watering on point to provide consistent moisture

I'll tag @Donothing-garden here to see if he's got time to reply with any info on Reactive Phosphate Rock

 

[VinDeezle]

Thats a lot of P for one pot tbh. At roughly 10% or more citrate soluble P that's more an amount you'd add to quite a few sq meters. I'd go with itchys advice to top dress a smaller amount if you go ahead. It will break down a lot slower than super phosphate and a tiny bit slower than soft phosphate as its not water soluble at all and will require citrates from microbial fixation to break down over time. I've only used it in a soil breaking/liming mix though (it has calcium and silica as well) so I haven't had any experience with it as a pure P source.

I'd start with a few Tablespoons for a pot that size, but even more importantly I'd wait for someone with more experience using it to chime in. In my opinion it is a good choice for use in medium that will be reamended/reused as it won't have much use in fast turnover situations. If you add it late flower, it'll start breaking down as the plant is finishing up due to the slow-release nature.

 

[VinDeezle]

Basically the "reactive" in the title just means it meets certain minimum standards for solubility (citrate and formic), and is usually lower in heavy metals than cheaper phosphate sources. It's not specifically a certain type or source of rock phosphate to clear it up, and analysis will vary with source. To simplify the whole scenario, just treat it like soft phosphate when it comes to application rates but live knowing it will mobilize quicker and possibly cleaner than cheaper phosphate sources in a microbially active, acidic soil.

1 cup per 50L is probably the absolute max you'd want to use in an inert/spent medium, but if you plan on adding other phosphate and Ca sources in the medium, 1/3 to 1/2 a cup per 50L should be a fine start in the base mix. One thing to keep in mind however If you are going to add other Ca sources, try to avoid too much carbonate as it can buffer out the acids needed to break down the phosphate. Gypsum being a sulphate is good alongside soft phosphate in comparison to a carbonate source.

 

[Donothing-garden]

T

Basically the "reactive" in the title just means it meets certain minimum standards for solubility (citrate and formic), and is usually lower in heavy metals than cheaper phosphate sources. It's not specifically a certain type or source of rock phosphate to clear it up, and analysis will vary with source. To simplify the whole scenario, just treat it like soft phosphate when it comes to application rates but live knowing it will mobilize quicker and possibly cleaner than cheaper phosphate sources in a microbially active, acidic soil.

1 cup per 50L is probably the absolute max you'd want to use in an inert/spent medium, but if you plan on adding other phosphate and Ca sources in the medium, 1/3 to 1/2 a cup per 50L should be a fine start in the base mix. One thing to keep in mind however If you are going to add other Ca sources, try to avoid too much carbonate as it can buffer out the acids needed to break down the phosphate. Gypsum being a sulphate is good alongside soft phosphate in comparison to a carbonate source.

This is a really clear explanation of rock phosphate, thanks. Combo of soft rock phosphate and fish bone meal is nice due to varying rates of release. And the solubilization of phosphate into plant available phosphorus is determined by microbial processes so make sure you have good levels of healthy soil biology for plant uptake. Also, phosphorus and calcium needs to be in the root zone for plant uptake via diffusion so if applying a phosphorus based fertiliser as a topdressing, work it into the top few inches of soil so it's broken down and taken up by the roots. You'll get stratification if scattered on top of the soil.

 

[Mellow oldfark]

What type of rock dust is it in 20 l buckets I've seen?
Would it be suitable for organic?

 

[Donothing-garden]

Not sure what type of rock dust you're referring to but it will be fine to use to amend soils. Extremely slow release trace elements.

 

[wigs]

Hi @itchybro, @VinDeezle and @Donothing-garden thanks for your replies. I ended up leaving it out of my base mix but will work it into the soil in the later part of the grow. Appreciate all the help and input - happy growing!

 

[Donothing-garden]

It takes a long time to become plant available so probably best to load up on it ahead of time. If you apply later, expect the P to become available in weeks/months

 

[wigs]

It takes a long time to become plant available so probably best to load up on it ahead of time. If you apply later, expect the P to become available in weeks/months

Hey @Donothing-garden - I have about 4 weeks left in my grow and we are in the beginning of flower phase - would it still be a good time to put in reactive rock phosphate, or am too late?