Can someone help me understand the differences 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 pic of the phosul bag

Thanks guys

 

[YumYum]

I think the 6% Phosphate is the number you should go by. Not sure where the other 10% of the Phospahte is but it must be permantly bound to something.

Calphos is 3% Phospahte and 20% Calcium so if you use half as much Phosul then you are only putting out 8% Calcium (in comparitive terms) and also some Sulfur which wasn't recommended.

Most soils are plentiful in Phosphorus since it doesn't tend to move through the soil. Is this for your garden or lawn? Did someone do a soil test or something?

 

[cpp gardener]

Check what the source is for Calphos and compare it to Phosul. That's where the difference in availability will come from. Use the 'available Phosphate' numbers to compare.

 

[Growdo Baggins]

I think the 6% Phosphate is the number you should go by. Not sure where the other 10% of the Phospahte is but it must be permantly bound to something.

Calphos is 3% Phospahte and 20% Calcium so if you use half as much Phosul then you are only putting out 8% Calcium (in comparitive terms) and also some Sulfur which wasn't recommended.

Most soils are plentiful in Phosphorus since it doesn't tend to move through the soil. Is this for your garden or lawn? Did someone do a soil test or something?

It's actuality for cannabis.

 

[YumYum]

It's actuality for cannabis.

I've never grown that so don't know of its nutrient requirements. If it is in the ground a a soil test would be best.

 

[cpp gardener]

Ahh, everything is illuminated. Use a water-soluble Bloom food like Greenlight 12-55-6.