I agree with Jim about phosphorus often seeming excessive in many formulations. I can't think of many soils in nature that would be especially high in P and arid climate soils especially are often very low in it. Perhaps something like 5-3-15 or 5-5-10 would be suitable for many bulbs. But it is often difficult to locate sources for unorthodox ratios once one moves away from 20-20-20 and the like. Dylan On Jan 30, 2008 2:53 PM, J.E. Shields <jshields@indy.net> wrote: > Diana and all, > > I agree with Diana --- my understanding from 30 years ago is that ammonium > nitrogen is absorbed under all conditions relatively poorly by plant > roots, > compared to nitrate. On the other hand, ammonium is the preferred form of > nitrogen for all fungi and many bacteria. Len Doran drove this point home > to those of us whom he undertook to coach: Ammonium feeds the pathogens > trying to kill your bulb, nitrate feeds the plant! > > In Narcissus poeticus (Vickery et al, 1946, cited in Rees) they found that > the plant tissue analyzed as follows: > > Bulbs grown on nitrate as source of nitrogen, 15.9 g N per 50 bulbs > Bulbs grown on ammonium as source of nitrogen, 14.0 g per 50 bulbs. > > My bibles, (post Doran), have been > > "The Growth of Bulbs" by A. R. Rees, pub. by Academic Press, New York & > London, 1972 > and > "The Physiology of Flower Bubls" by A. de Hertogh and M. Le Nard, pub. by > Elsevier, Amsterdam & New York, 1993 > > The point made by Doran was the same as that made by Rees: Bulbs need > nutrients in the approximate ratio the nutrients occur in the healthy bulb > tissue. Plants are also limited by any nutrient that is present in > significantly less than needed levels. Unfortunately, only Gladiolus, > Lilium, and Tulipa have been studied in detail. As a general thing, the > ratio of N, P, and K in plant tissue is about 4 N to 0.3 P to 2 K. The > precise ratios can vary not only from genus to genus but from cultivar to > cultivar. > > The question of the effects of nutrient ratios on efficiency of absorption > is not resolved so far as I can recall -- or my knowledge may be decades > out of date. I am not aware the N, P, and K affect each others absorption > rates. > > Mg (magnesium), Ca (calcium) and K (potassium) are similar in ionic charge > (Mg and Ca) and in size (Ca and K) and are said to be able to interfere > with each other's absorption. This alone might indicate that applying > calcium at a different time than magnesium would increase the > effectiveness > of the applied nutrients. > > Loading the fertilizer up with phosphate is relatively harmless in > soilless > growth medium. In soil, excess phosphate can tie up iron, calcium, and > probably a couple of the trace elements, depending on the ambient soil > pH. Phosphate is of course essential for plant growth, but in > significantly smaller amounts that N and K. I've never understood where > people are coming from when they recommend high phosphate fertilizers; > this > just does not make physiological sense to me. > > Jim Shields > in cold central Indiana (USA) > > > At 01:12 PM 1/30/2008 -0800, you wrote: > >It is also my understanding that nitrate nitrogen, in the form of > potassium > >nitrate or calcium nitrate, is better absorbed at lower temperatures, so > >this is important for those bulbs that grow during the winter. The > >formulation I use has both ammonium nitrite and potassium nitrate, but > the > >main ingredient is potassium nitrate. > > > >Diana > >Telos Rare Bulbs > > ************************************************* > Jim Shields USDA Zone 5 Shields Gardens, Ltd. > P.O. Box 92 WWW: http://www.shieldsgardens.com/ > Westfield, Indiana 46074, USA > Tel. ++1-317-867-3344 or toll-free 1-866-449-3344 in USA > > > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://www.pacificbulbsociety.org/list.php > http://pacificbulbsociety.org/pbswiki/ >