Hello Horacio; >Hello I have a question:
>Actually my plants grown very well with foliar fertilizers(Wuxal, Nitrofoska), but these fertilizers do not contain calcium. it is necessary to apply calcium to the orchids? The calcium is associate to the flowering?< Both calcium and magnesium are necessary for good plant and root growth, and so affect flowering more indirectly than potassium, phosphorus and trace elements. To my knowledge, there are two reasons for omitting calcium in many fertilizer formulae: 1) Calcium (as nitrate, for example) can interact with the phosphate component and render much of the phosphate unavailable to plants as a nutrient More pertinent to your question: 2) Tap water sources generally have magnesium and calcium as carbonates (water 'hardness') - not the most ideal form as the carbonates accumulate in pots and especially on rafts or plaques, due to higher evaporation and can raise the pH to a level which could inhibit plant growth or root development. However, calcium is there unless RO water is used and the plants use it to an extent. Relying on water supply to provide enough calcium/magnesium however is a very inexact science; some areas might have very little while others very probably will have it in excess. I hear that in Little Rock, Arkansas if you have a shower you wind up with stalactites in your hair. --------------------------------- What works well for me is to modify the tap water pH towards about 6 with citric acid, which turns the water hardness into calcium and magnesium citrates. You still end up with the same white deposit on the soil surface of house plants, but with an important difference - the pH of the deposit turns out to be around 6, and surface roots can be seen to be growing adjacent to this unaffected, unlike with carbonate buildup. Here, the implications are important for plaque-mounted plants. Many mineral citrates are almost insoluble but nevertheless act as slow-release fertilizer with an inherently ideal pH in the case of calcium & magnesium. Apparently citrates are found in all plant tissues, so this might be another reason to use citric acid, and citrates may not upset the NPK balance as when nitric acid is used instead. I can afford to mess around with citric acid because I only have about 300 plants. I'm no chemist and there may be those on this list who know more about this than I do, so I'm ready to stand educated... Regards Dave - >As my old granny Flora used to say, "The more you know, the less the better" > -- Billy Connolly
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