How much NPK to add to the soil?

[Phillybonker]

I have added blood and bone with a NPK of 10-4-0.2. I added about half the recommended amount (two handfuls per sq metre). I also have 60 litres of compost down for each plant.

Now I want to add seabird/bat guano in liquid form to the soil because the phosphorus from the bone meal won't be available for a few months when my plants will be almost finished, so I need a fast release fertilizer phosphorus source like guano liquid.

The guano liquid has a NPK of 10-10-2.

The blood & bone and guano liquid will have a combined NPK of 20-14-2.2. If you take into consideration the phosphorus will not be available for a few months, that deducts it to a NPK of 20-10-2.2. Now if you factor in the NPK of the compost 2-1-1 (Guessing) that leaves us with a NPK of 22-11-3.2. Likewise, if you factor in that I only gave the plants half recommended amount of Blood & bone, that leaves us with a NPK of 17-11-3.2, I think?, please correct me if my calculations are wrong. Anyway, my question is: Will this be too much nitrogen for the plants to handle....NPK: 17-11-3.2

 

[Phytoplankton]

Sounds like you’ve got a lot of nutes in there. Remember, while in veg the plants need a lot of N and some P&K, that changes during preflower/flower, then you want more P&K and less N, so you might want to delay adding too much P&K.

 

[Phillybonker]

Sounds like you’ve got a lot of nutes in there. Remember, while in veg the plants need a lot of N and some P&K, that changes during preflower/flower, then you want more P&K and less N, so you might want to delay adding too much P&K.

At the moment I have an estimated (available) NPK of 12-1-1. I'm excluding the bone meal because the P won't be available yet.

I'm growing organically so I assumed the plants will only take from the soil what nutrients they want. So even if I have too much P&K in the soil I assumed the plants will ignore it and go for the N.

 

[Phytoplankton]

I’d just find a organic fert with P&K, add that, and be done with it, you have a lot of N already. Not being an organic grower, There are certainly things I simply don’t know, but I do know that you can overfeed or have too hot of a soil. I’ve overdone it on N, and the results are quickly observable both in seedlings and established plants.

 

[SmokingWings]

@Phillybonker , if only it was that easy and simple. I did the same sort of calculations but figured I was not doing the math right. Just adding up the N-P-K numbers does not work. One thing that occurred to me is if I kept adding fertilizers to the mix and kept adding the numbers eventually I would have something that was over 100% Nitrogen and that made no sense at all.

It has been 2 years, maybe more, but at one time there was a discussion on how to do the math. This math involves averaging out the NPK for each individual fertilizer that will be used. Then some adding and more division. And the weight of all the fertilizer mixes have to be known and used in the calculations. Just taking 2 handfuls of this and a gallon of that and a 5 pound bag of that does not work (well it probably works but it will be a lot more calculating). The compost mixed in the soil does have measurable amounts of N-P-K but those numbers are rarely part of the calculations.

I am with @Phytoplankton on this and the easiest thing to do is find organic fertilizers that have the P and K that you want without the N, or at least a very low amount of available N. Bat Guano, Seabird Guano, Rabbit Manure all have a good amount of water soluble P. On the other hand, Bone Meal and Rock Phosphate have good amounts of P but they take longer to breakdown and make P available beyond the initial water-soluble amounts.

 

[FelipeBlu]

Highya!

The NPK shown on the labels are percentages by weight. So, if you have 100 grams of the 10-4-0.2 weighed out, there should be at least (manufacturers only have to show the minimum) 10g of N, 4g of P2O5, and 0.2g of K2O. If you then add 100 ml of the liquid guano (10-10-2), you need to consider the density of the liquid. If the net wgt is 1200g and the volume is 1L, the density is 1.2 - you multiply your percentages by this to get the resulting NPKs.
So, you will get 12g N, 12g P2O5, and 2.4g K2O from that 100ml.
Now, you add that to 10 kilos of soil. Your N & P2O5 percentages will both be 22g/10000g soil = 0.22%
I’ll let you figure out the K2O.
You also need to multiply the P2O5 result by 0.43 to obtain just P, and multiply K2O by 0.83 to obtain just K.

By the way, those two components are not providing enough K. What else do you have?

 

[Phillybonker]

Highya!

The NPK shown on the labels are percentages by weight. So, if you have 100 grams of the 10-4-0.2 weighed out, there should be at least (manufacturers only have to show the minimum) 10g of N, 4g of P2O5, and 0.2g of K2O. If you then add 100 ml of the liquid guano (10-10-2), you need to consider the density of the liquid. If the net wgt is 1200g and the volume is 1L, the density is 1.2 - you multiply your percentages by this to get the resulting NPKs.
So, you will get 12g N, 12g P2O5, and 2.4g K2O from that 100ml.
Now, you add that to 10 kilos of soil. Your N & P2O5 percentages will both be 22g/10000g soil = 0.22%
I’ll let you figure out the K2O.
You also need to multiply the P2O5 result by 0.43 to obtain just P, and multiply K2O by 0.83 to obtain just K.

I applied 200g of blood & bone to 2 x square meters. So that's 20g of N, 8g of P (unavailable), and 0.4g of K.

I will be adding 5mg of guano liquid concentrate. So it will be 0.6g N, 0.6g P, and 0.24 K, I think??

I'm not very good at math.

By the way, those two components are not providing enough K. What else do you have?

I have potash which I'll add two weeks before the start of bloom.

 

[FelipeBlu]

You may see K def before then. Cannabis loves K.

 

[bobrown14]

Caclulating NPK...

I'm going to blow the numbers out of the water and here's why:

N = the % of Nitrogen.... However:

"The following will help you convert to % P and % K:

• P2O5 consists of 56.4% oxygen and 43.6% phosphorus by weight. To get the % P value, multiply the reported NPK value by 0.436, or approximately half of the reported value.

• K2O consists of 17% oxygen and 83% potassium by weight. To get the % K value, multiply the reported NPK value by 0.83.

Using this information you can see that a fertilizer NPK number of 10-10-10 contains 10% nitrogen, 4.36% phosphorus, and 8.3% potassium."

Now I'm an organic farmer so all of this is mute and I grow microbes and fungi and supply a soil mix that has more than enough of everything so the microbes/fungi/plant roots can do their thing.

It's good to not over do and over think. Compost portion of the soil mix is key.

 

[SmokingWings]

There is a point we get to where we are overthinking our problems and their solutions.

This thread is an example of why many growers will purchase a line of fertilizers and nutrients and follow the schedule given by the company. Or, chose the already mixed fertilizer and then build a custom schedule. Both have their advantages and either can be used to produce a successful harvest.

I gave up trying to custom mix fertilizers. A better solution to the problem and one that is showing signs of success was to purchase different products off the shelf, try them out, and then customize the schedule to include the ones that produced the results.

 

[bobrown14]

Build a proper soil
The plants will grow.

 

[NOOOBIENOT]

I really hope you plan on cooking any of these mixes before you even think about putting a plant in these soils for at least 30 -45 days minimum and you are using r.o. water ,other wise you are setting your self up for a long hard road of problems , organic is a feed the microbes (bacteria , fungi , protozoa etc ), they feed the plant , and ph doesn't mean a thing , the microbes worry about that for you , get the book organic t.l.o. growing by the rev , it explains it all . here are my organic plants and i followed his ideas and tweaked them a little due to the fact i grow in in either 10 or 20 gallon pots

 

[Phillybonker]

Caclulating NPK...

I'm going to blow the numbers out of the water and here's why:

N = the % of Nitrogen.... However:

"The following will help you convert to % P and % K:

• P2O5 consists of 56.4% oxygen and 43.6% phosphorus by weight. To get the % P value, multiply the reported NPK value by 0.436, or approximately half of the reported value.
• K2O consists of 17% oxygen and 83% potassium by weight. To get the % K value, multiply the reported NPK value by 0.83.

Using this information you can see that a fertilizer NPK number of 10-10-10 contains 10% nitrogen, 4.36% phosphorus, and 8.3% potassium."

Now I'm an organic farmer so all of this is mute and I grow microbes and fungi and supply a soil mix that has more than enough of everything so the microbes/fungi/plant roots can do their thing.

It's good to not over do and over think. Compost portion of the soil mix is key.

I can't understand the math but then again I never was good with numbers. I think on their next feeding cycle I'll give a couple of plants a little guano liquid and see how they respond to it.

 

[Phillybonker]

Build a proper soil
The plants will grow.

I'm hoping 60 litres of high grade compost per plant site, plus blood & bone and seaweed liquid will give me a proper soil.

 

[Phillybonker]

A better solution to the problem and one that is showing signs of success was to purchase different products off the shelf, try them out, and then customize the schedule to include the ones that produced the results.

I'm going to do some experimenting with different fertilizer combinations on my next grow. For this grow, I've already got a lot of nutrients in the soil and have to be careful not to add too much of anything else.

 

[Phillybonker]

I really hope you plan on cooking any of these mixes before you even think about putting a plant in these soils for at least 30 -45 days minimum and you are using r.o. water ,other wise you are setting your self up for a long hard road of problems , organic is a feed the microbes (bacteria , fungi , protozoa etc ), they feed the plant , and ph doesn't mean a thing , the microbes worry about that for you , get the book organic t.l.o. growing by the rev , it explains it all . here are my organic plants and i followed his ideas and tweaked them a little due to the fact i grow in in either 10 or 20 gallon pots

I think it's just manure that needs time to cook, otherwise cooking is for the kitchen.

i did however add the ingredients to the soil 3 weeks prior to transplanting to give time for the microbes to break down the blood & bone.

I've heard of Organic TLO and I'll give it a read, Thanks mate

 

[Jefferyol]

I have added blood and bone with a NPK of 10-4-0.2. I added about half the recommended amount (two handfuls per sq metre). I also have 60 litres of compost down for each plant.

Now I want to add seabird/bat guano in liquid form to the soil because the phosphorus from the bone meal won't be available for a few months when my plants will be almost finished, so I need a fast release fertilizer phosphorus source like guano liquid.

The guano liquid has a NPK of 10-10-2.

The blood & bone and guano liquid will have a combined NPK of 20-14-2.2. If you take into consideration the phosphorus will not be available for a few months, that deducts it to a NPK of 20-10-2.2. Now if you factor in the NPK of the compost 2-1-1 (Guessing) that leaves us with a NPK of 22-11-3.2. Likewise, if you factor in that bamboo fertilizer only gave the plants half recommended amount of Blood & bone, that leaves us with a NPK of 17-11-3.2, I think?, please correct me if my calculations are wrong. Anyway, my question is: Will this be too much nitrogen for the plants to handle....NPK: 17-11-3.2

Blood meal, composted manure, used coffee grounds, and alfalfa pellets are all nitrogen-rich soil amendments. Tomatoes are heavy feeders, and the best fertilizer for them depends on their stage. Nitrogen is used by plants when they are growing. Phosphorus is required to stimulate fruiting, while potassium is required for root structure and fruit set. Calcium is essential for preventing blossom end rot.

If it were me, I'd start with a quick (like blood meal) and slow (like composted manure or coffee grounds) release source of nitrogen, then transition to a commercial tomato fertilizer mix with beneficial microbes when the plants begin to flower.

 

[Phillybonker]

Blood meal, composted manure, used coffee grounds, and alfalfa pellets are all nitrogen-rich soil amendments. Tomatoes are heavy feeders, and the best fertilizer for them depends on their stage. Nitrogen is used by plants when they are growing. Phosphorus is required to stimulate fruiting, while potassium is required for root structure and fruit set. Calcium is essential for preventing blossom end rot.

If it were me, I'd start with a quick (like blood meal) and slow (like composted manure or coffee grounds) release source of nitrogen, then transition to a commercial tomato fertilizer mix with beneficial microbes when the plants begin to flower.

I just put a scheduled feed of blood & bone down on a couple of plants, I also gave the plants some guano liquid, so there is a lot of N and P in the soil. If there is going to be any nute burn/lockout I'll probably won't see it for 2-3 weeks. If I remember I'll post an update on what happened.

 

[bobrown14]

I'm going to do some experimenting with different fertilizer combinations on my next grow. For this grow, I've already got a lot of nutrients in the soil and have to be careful not to add too much of anything else.

Try doing a top dress of leaf mold - can get that in the woods where all the leaves are. Just get a wheel barrow and cart some to your grow site. Thats the best thing you can add and it lasts a few years.