How much phosphorus should i put in my outdoor soil ?

[Gizmo]

Hello guys, i hope you are well, its outdoor time and i must say better late than never, and im a little late on my outdoor grow and i need a little help please.

I found a nice forest of brambles/thorns 6-8 foot high near a river and i cleared a small nice patch facing south with a manual hedge trimmer, a gardening handsaw and some special gloves for thorns. it was fun and i prune a nice tunnel in the brambles. now i would like to prepare my soil with a few nutrients before planting end of june. i know its late to prepare the soil but as i said better late than never.

My plan is to check the pH of the soil and adjust with dolomite lime if necessary, add a nice organic fertilizer 7-6-12+4Mgo i bought and add some more phosphorus, here is my problem :

i follow a soil recipe where they add the organic fertilizer 7-6-12+4Mgo and some guano kalong 1-10-1+15Ca. i want to replace the guano kalong with a phosphorus organic fertilizer, its a 29% total phosphoric anhydride (P2O5) with 79% soluble in formic acid.

How much of my phosphorus nutrients should i add to replace the guano kalong 1-10-1 ? my phosphorus nutrients is almost three times stronger in P than the guano kalong so should i put three times less ?

does the two nutrients souces have the same availability of phosphorus ?

The manufacturer advise very low dosage compared to my calculation.

they advise 60 g / m² for the preparation of the soil
50 g / m² for planting flowers and vegetables
150 g / m² for planting fruits trees or ornemental trees

i calculated more than 400g / m² to replace the guano.

please advise me as i dont want to burn the plants and have some nutrient lockout.
thank you very much

Gizmo

Edit, i always posted the soil recipe in another thread but here it is, its Soma soil recipe :

50L worm castings
3 x 50L black peat
50L Organic potting soil
3 x 50L bags of Bio Bizz Light-mix
2KG Guano Kalong
2kg DCM organic fertilizer 7-6-12+4Mgo
1/3 of a 30L bag of perlite (10L)
2KGs Maerl (sea chalk for PH)

 

[cbcool]

Based on the math of available phos it would be about 1.4lbs to replace the guano. I would add about 5lbs of gypsum to that mix as well, but that's just me. Hope this helps.

 

[Gizmo]

thank you cbcool, did you calculate with the 79% soluble in formic acid ? i dont now what formic acid is and what it means, i supposed it means only 79% of the phosphorus is available to the plant, i dont know if the 10% phosphorus of the guano is 100% available either so im a little lost, im a very simple farmer who try to understand
gypsum i read only good thing about it but we dont have it available easily here, dolomite lime from algae/seaweed is more common to use.

 

[cbcool]

Nope I missed the 79% soluble part, that would be 1.9lbs then, but its always better to error on the light side. You can always add more , its harder to take it out. I would water in good for a couple of weeks before you put the plants in the ground just be safe.

The label on the guano should say what's total and what's available.

 

[Gizmo]

thank you cbcool, yes i plan to water well after the amendment and let the soil rest for 2 weeks before planting. the thing who bother me is the dosage advised by the manufacturer of the phosphorus, i believed the nutrients need of Cannabis was very close to tomatoes and the manufacturer advise only 50 g / m² for planting vegetables so im a bit afraid to put 16 times the dosage advised by the manufacturer. on the other side i really want to have a good soil need more advices

 

[MJPassion]

A soil test & some math will get you a lot better answer.

 

[Gizmo]

unfortunatly i have no access to laboratory test soil here and i cant order a soil test i have not the time and im not sure it will help me so much, it will complicate but more importantly i have not the time to order, im a bit hurry to prepare my soil. what im really trying to know is the equivalence between the guano kalong 1-10-1 and the 29% phosphorus nutrient. the manufacturer only advise 50g per square meter for planting vegetables, thats whats bother me.

 

[cbcool]

If you're Leary about burning, start with a small amount and see how they react after you put them in the ground. You can always add more by top dressing and water it in.