Hi all,It is going to depend on the plant, but plants need about x10 more nitrogen (N) and potassium (K) than they do phosphorus (P), and about x3 times more phosphorus than they do any of the other <"
essential mineral nutrients">.
Nitrogen, P & K are thenthree "macro-nutrients".
Some plants are adapted to <"
rapid growth in high nutrient"> (<"
eutrophic">) conditions, if you like <"
everything is turned up to eleven">, others aren't. The leaf colour of a non-CO2 limited plant is usually <"
a good indicator of nitrogen content">. I just look at the plants, they never lie.
Deficiencies of macro-nutrients usually show up in restricted plant growth and relate to actual amounts, deficiencies of the other nutrients may be due to a total absence, but more usually relate to ratios and interference in uptake. Nitrate and potassium compounds are all soluble, so you don't have problems with the NO3- and K+ ions coming out of solution, but some phosphorus compounds are insoluble, and PO4---- ions readily form calcium/iron etc phosphates, particularly in alkaline conditions.
Analytical techniques can find deficiency symptoms, but because you are looking for very small amounts, and ratios may be more important, it is fairly problematic.
If you have time have a read through all the linked threads (like <"
How much carbon in ..">) in this post, they have a lot of useful posts in them, and links to scientific journal articles etc.
cheers Darrel