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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.
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.