Availability

[headfullofbees]

When you see NPK numbers on fertiliser boxes or tubs, it's very tempting to think that bigger means better, and that the higher the numbers, the more of these nutrients your plants will be able to access.
This seems to give petrochemical fertilisers an unassailable advantage, when you compare them with organic feed.
This is not necessarily the case though.
I use seaweed as a fertiliser, its NPK numbers are 0:0:1, and yet all my fellow allotment-growers would kill for enough for their potatoes.
Similarly, pelleted chicken manure has quite low NPK numbers (4:3:2.5) but is again hugely popular with grow-your-own gardeners, many with four or five decades of experience.

You see, there's far more to it than bald numbers.
If I make up some Miracle gro like fertiliser, and feed my plants with it, the nitrogen is absorbed very quickly, but much of the phosphates and potash are in forms which either are much more slowly usable, or not directly at all!
So your plants have run out of nitrogen, and need more, whilst there is still plenty of potash/phosphate in your growing medium.
So the following week you feed again, and the next week, and the next...
Before you know it, your compost, soil, whatever, is a toxic mix of salts, less and less able to feed your plants, so you increase the doses, in a vicious spiral of diminishing return and soil toxicity.

Chicken manure, however, releases the nitrogen more slowly, so that your plants have the opportunity to use the PK components too, without toxic build up.
Similarly, the potassium levels in seaweed are quire low, but it is AVAILABLE to the plants and is not poisoning the soil with anything else whilst it works its magic.

Compost tea is great, because it increases microbial activity in the soil, making the nutrients already present in the soil available to your plants.

So next time you see huge NPK numbers on a box of petro-gro, remember, if you walk that road, pretty soon these huge numbers will not be enough.

 

[firelily99]

Excellent article, a very valuable post to organic gardeners or gardeners hoping to go organic. Many misconceptions about fertilizer exist and it plays to the advantage of the petrochemical fertilizer manufacturers.

 

[zigs]

Well written Bees

I'll be sticking with my seaweed, wood ash and nettle feeds

 

[Chuck]

When you see NPK numbers on fertiliser boxes or tubs, it's very tempting to think that bigger means better, and that the higher the numbers, the more of these nutrients your plants will be able to access.
This seems to give petrochemical fertilisers an unassailable advantage, when you compare them with organic feed.
This is not necessarily the case though.
I use seaweed as a fertiliser, its NPK numbers are 0:0:1, and yet all my fellow allotment-growers would kill for enough for their potatoes.
Similarly, pelleted chicken manure has quite low NPK numbers (4:3:2.5) but is again hugely popular with grow-your-own gardeners, many with four or five decades of experience.

You see, there's far more to it than bald numbers.
If I make up some Miracle gro like fertiliser, and feed my plants with it, the nitrogen is absorbed very quickly, but much of the phosphates and potash are in forms which either are much more slowly usable, or not directly at all!
So your plants have run out of nitrogen, and need more, whilst there is still plenty of potash/phosphate in your growing medium.
So the following week you feed again, and the next week, and the next...
Before you know it, your compost, soil, whatever, is a toxic mix of salts, less and less able to feed your plants, so you increase the doses, in a vicious spiral of diminishing return and soil toxicity.

Chicken manure, however, releases the nitrogen more slowly, so that your plants have the opportunity to use the PK components too, without toxic build up.
Similarly, the potassium levels in seaweed are quire low, but it is AVAILABLE to the plants and is not poisoning the soil with anything else whilst it works its magic.

Compost tea is great, because it increases microbial activity in the soil, making the nutrients already present in the soil available to your plants.

So next time you see huge NPK numbers on a box of petro-gro, remember, if you walk that road, pretty soon these huge numbers will not be enough.

Excellent post. It is hard to explain more is not necessarily better. Have you ever noticed that commercial organic fertilizers rarely exceed 13 total on the NPK and chemicals usually start out at about 13 just for nitrogen? It's no wonder it burns up organic matter in the soil

 

[headfullofbees]

Plants initially take a very fast jump forward with petro-gro as they get that nitrogen boost, and this is very seductive for inexperienced grower, who probably thinks, "Wow! This is great stuff!" and carries on using it, never thinking about the sustainability of it, or why, with this stuff on the go, there's problems all over the planet with soil depletion.

Now I'm not Chuck, I'm miles behind him in growing organically, but I can still remember what seduced me about petro-gro, and perhaps sympathise a bit with non-organic growers
But I'm converted.
It's taken me a while to sort out my garden, and "fortunately" my allotment hasn't been cultivated much in the past five years, so much of the petro-gro should have sluiced out.