Could someone help me understand the difference between these 2 labels please?

[Growdo Baggins]

I've gotten a recommendation for amending my soil. It calls for 1 cup calphos (soft rock phosphate) which is 0-3-0. It says it has 3% available P with 15% or so total P. I've locally source an amendment called Phosul. It's labeled 0-16-0. But it says on the bag 16% total P and 6% available P. But it's labeled 0-16-0. So if I'm subbing out the phosul for the calphos I should do the math based on it having 6% available P and ignore that it's labeled 0-16-0. 1 cup of calphos at 3% available P would be .5 cup of phosul at 6% available P to equal the same amount of available P. If I do the math by the label 0-16-0 vs 0-3-0 it would be .2 cup of phosul (rounded up) to equal the same amount. I'm new at this. Is it just labeling differences between different manufacturers? I should trust the 6% available P, correct?

Here's a picture of the phosul

Thanks for any help.

 

[Creeperpark]

Good question. The bottom numbers are what you go by. It doesn't make any difference because your plant can only take what it needs at any time. Out of all the nutrients in a container, most are not even used and are added for overkill.

 

[Growdo Baggins]

So what you're saying is if I don't get the conversion exactly right it's not going to matter much, bc the plant is only going to take what it needs. Unless I'm way off it's not going to matter much

 

[Thcvhunter]

Go by available.
But, also keep in mind the total number (16) as that will linger and if you reuse soil, it could bit ya after 2 or 3 recycles.

When mixing soil, most people think of it as a super soil for peak flowering. And that will kick ya in the ass when sprouting and vegging.
Any time you amend and/or reamend, its best to add a little bit several times, rather than add it all all at once

 

[KIS]

I agree with other comments. Go with available P. So apply 1/2 the amount if the recommendation was based off of 3% available phosphate.

Also keep in mind though that the total P you're adding will lower pH and raise soluble salts and you'll want to work towards making the P in your soil more available over time. This is typically a microbial process, something that most growers in this forum already have good practices for.

Lastly, I look at a lot of soil tests and we see high P on the Meilich III test but low available P on the saturated paste and I don't freak out because I usually don't see P deficiencies if the total P in a soil mix is high even if it's not showing as available on the saturated paste. I attribute this to the greater microbial activity and biomass in our "living soils" than you would find in agricultural soils typically.

Hope that helps!

 

[Growdo Baggins]

I understood a lot of that and it helped, but it left me with some questions.

I've read the Intelligent Gardener and am slowly getting a grasp, but how does the total P I'm adding lower ph and raise soluble salts? The ph I might understand. Is it bc it's filling more of the TEC with Phosphorous cations and that's lowering the ph?

The soluble salts is really the thing I'm trying to figure out the most right now. How are the organic amendments adding salts? I thought salts came from chemical fertilizers. My soil test came back with high salt concentrations. I've only added compost/ewc, aeration and peat. So I can assume the salt came from the lobster compost I used. Also on the saturated paste my available P was high at 6.59. I guess bc of the compost as well. But where are the salts going to come from if I'm only adding organic amendments? How are they coming from the added P?

I've actually been working with you guys at KIS and Brandon's been incredibly helpful. He's had several phone conversations with me answering differently questions I've had about the soil recommendation he did. Ben's been awesome with helping with the blumat set up too. We'll see how the grow goes though, lol. I'm jk. I would've def just used your "water only biochar soil" but shipping to the east coast was a killer. I've learned a lot through the process of making my own though.

Thanks for the help dude.

 

[KIS]

Keep in mind that all nutrients are either cations or anions. Cations like Ca, Mg, K, Na, etc....will all raise soil pH. Anions like P, S, and Nitrate will lower pH. They are also all "salts." This is not a reference to sodium like we use in everyday language, and no salts are not just for chemical fertilizers.

http://hort.cornell.edu/gardening/soil/salts.pdf

Sodium is a separate issue, as it's not an essential plant nutrient and we want to limit it as much as possible in soils (for the most part).

That is extremely high P for a paste test. That makes me think you are using fish hydrolysate or pH down or something else that contains phosphoric acid. I've also seen those kind of numbers with some guanos.

 

[Growdo Baggins]

Keep in mind that all nutrients are either cations or anions. Cations like Ca, Mg, K, Na, etc....will all raise soil pH. Anions like P, S, and Nitrate will lower pH. They are also all "salts." This is not a reference to sodium like we use in everyday language, and no salts are not just for chemical fertilizers.

http://hort.cornell.edu/gardening/soil/salts.pdf

Sodium is a separate issue, as it's not an essential plant nutrient and we want to limit it as much as possible in soils (for the most part).

That is extremely high P for a paste test. That makes me think you are using fish hydrolysate or pH down or something else that contains phosphoric acid. I've also seen those kind of numbers with some guanos.

All I've mixed is the coast of maine compost and ewc, aeration and peat. It's a lobster compost. I sent in my own water. Is the available P so high that it's going to lockout other nutrients you think?

Thanks for the link. If you've got anymore please send them my way.

 

[Growdo Baggins]

I was reading through a book on soil enzymology and came across this line,

"Chemically, humus represents a mixture of decomposed or altered products of carbohydrates, proteins, fats, resins, wax, and other similar substances. These complex compounds are gradually decomposed by soil organisms into simple mineral salts, carbon dioxide, water, organic acids, ammonia,
methane, and free nitrogen, depending upon the initial composition of the organic matter."

So the salts are the minerals that the organic amendment breaks down into. I'm sorry if this is a stupid question but I'm going to throw this out there for anyone to answer. For example, in a soil that has good microbial life and a shit load of amendments added, the soil organisms would break down so many of the amendments into mineral salts that it would create a build up. Bc the plant can't use them all. Why couldn't you just not feed your plant until it used up all the excess salts?

 

[Three Berries]

Salts are the single mineral content of compound mineral. Your nutes without water are the salts. If you use dry nutes to mix it's obvious. If you water to run off every time the salt build up shouldn't be a problem. You have to have the right perlite mix or it takes forever to use up the water between waterings.

I used hard well water and watered to run off just a couple of times through the grow, not enough perlite. Got one plant locked out with yellow leaves and purple stems though is stretching more that the other two. The run off was 7.7! The other two were at 7.0.

I watered to run off with 5.0 rain and nutes last night. and got 6.9 out of the high one. They are 3 weeks into flower and I'll water to run off more through the rest of the grow.

I have been foliar feeding them twice a day too with Ca, Mg and K chloride compounds. I usually have a bad K issue now but am avoiding that for the time being except the high pH one.

The high pH one has the top shoot nodes stretched out much more that the other two.

 

[St. Phatty]

I've gotten a recommendation for amending my soil. It calls for 1 cup calphos (soft rock phosphate) which is 0-3-0. It says it has 3% available P with 15% or so total P. I've locally source an amendment called Phosul. It's labeled 0-16-0. But it says on the bag 16% total P and 6% available P. But it's labeled 0-16-0. So if I'm subbing out the phosul for the calphos I should do the math based on it having 6% available P and ignore that it's labeled 0-16-0. 1 cup of calphos at 3% available P would be .5 cup of phosul at 6% available P to equal the same amount of available P. If I do the math by the label 0-16-0 vs 0-3-0 it would be .2 cup of phosul (rounded up) to equal the same amount. I'm new at this. Is it just labeling differences between different manufacturers? I should trust the 6% available P, correct?

Here's a picture of the phosul
View attachment 18815798

Thanks for any help.

Mix a small amount of each in 2 or more different soil samples.

Let it sit a few days.

Measure the pH of the run-off.

Got to be patient & thorough.

The good news is, the plants will love the Phosphorus - when it's delivered at the right pH.

Phosphorus at the wrong pH is like hooking up 10,000 volts to a hamburger and handing it to a hungry person.

pH doesn't exactly measure voltage, it measures Hydrogen+ ions and sometimes OH- ions.