Phosphorous in Fertilizers

[Wayne R]

As I pursue a steep Bonsai leaning curve I'm trying to get my head around fertilizers... specifically NPK ratios and which element does what. Just when I thought N was for leaves, P was for roots, K was for showy bits and all I had to do was get the ratios balanced, I came across this article that seems to blow the need for Phosphorous in non-agricultural environments out the window.

Comments?

Wayne

[Bush bunny]

N - Nitrogen (essential for tree growth and health, and can only be obtained through hair roots, when the microorganisms eat bacteria and then digest it, then the roots can absorb it. And to convert into energy and growth.
P - Phospherous
K - Potassium.

Ironically we humans need a balance of these elements too. 78% nitrogen in the air we breathe, and Phospherous and calcium in our bones. And potassium to regulate and control the other elements.

A balanced liquid or solid fertiliser will have the proportions they come in.
Others might have no nitrogen content, advised for some bonsai, during late summer and autumn and no fert until they start budding up in spring. Each species has special requirement. Any gardening book will tell you how to spot a deficiency mainly in the leaves of plants and trees.

Really without a mineral soil test, other than p.H, one can't really tell the proportions of minerals and inorganic matter. But as a guide. Soil and potting mixes, should have 45% minerals, 5% organic matter, 25% of air and 25% of water.

[treeman]

Yes P is not needed in anywhere near the concentrations usually available. There have been quite a few trials to determine the efficacy of ''Bloom Booster'' fertilizers and no evidence has been found to support the idea that high P boosts flowering.
One study with African violets actually found a reduction in flowering when a popular high P A/violet fertilizer was used. It is still commonly available!

You commonly read that the Japanese recommend higher P for flowering species. This is because they use low P rape seed with Akadama which is a clay and clay has been known to strongly bind P. Hence the need for the addition of bone meal for flowering species. It is especially noteworthy that too much soluble P can inhibit and even kill mycorrhiza! So if you want your pines (and many others) to do well, ease up on the P.

The recommendation for high P is a hangover from when potting mixes contained soil. Modern mixes based on bark and inorganic product do not need more P than the average. A P to N ratio of about 0.2 is fine for most situations. You can work this out dividing the % of P in your favorite fertilizer X the % of N on the packet.

[Brad75]

Hi all,

I was taught that P or Phosphorous is basically the chemical element that guards against disease in plants. It'll be included in general fertilisers to some degree so don't worry about adding any- just fertilise generally and enjoy the bonsai process!

Cheers,

Brad75.