Hi all, I suggest we consult the following: A.R. Rees, "The Growth of Bulbs" Academic Press, London & New York, 1972, 311 pp. A. De Hertogh & M. Le Nard, "The Physiology of Flower Bulbs" Elsevier, Amsterdam, London, New York, Tokyo, 1993, 811 pp. This was gleaned from de Hertogh & Le Nard: For Narcissus, phosphate and potassium are applied at planting and then nitrogen later as a top dressing just before plant emergence. Dutch usage seemed to average 50-75 kg/hectare ( 1 kg = ca. 2.2 pounds; 1 hectare (ha) = about 2.5 acres) nitrogen in winter; 75-125 kg/ha nitrogen in spring; 100 kg/ha phosphate (as P2O5), and 220 kg/ha potassium (as K2O), and 40-60 kg/ha magnesium. Tulips are given fall and spring fertilizer applications: Ammonium in fall; a small but measurable uptake of nitrogen occurred in winter. The spring application is nitrate (NO3-) applied at leaf emergence; uptake was rapid. Excessive nitrogen (more than 250 kg/ha) caused a decrease in bulb yield. Potassium and phosphate fertilizers have not be studies so thoroughly Lilium were fed with 75-150 kg/ha nitrogen in mid-May or split between mid-May and mid-June applications. The split applications yielded large bulbs. Use of potassium fertilizer in magnesium-deficient soils will exaggerate the magnesium deficiency. Unless you are doing a large scale study of bulb yields, it probably won't matter what you use or when you use it to feed bulbs. It is in the tricky ones where you need to experiment and to be aware of what you are doing. Field trials do not have much relevance to pot culture, in my own opinion. Regards, Jim Shields in spring-like central Indiana At 11:59 AM 4/8/2005 -0400, you wrote: >........ >But here's another thought: I've been thinking about this question of >fertilizing bulbs a bit lately, and this idea popped up: why not see what >the experts, the real experts whose livelihood depend on the results, have >to say about it. > >I have not yet tracked down the experts, but for starters I'm considering >USDA publications on onion culture and Easter lily culture. Those are both >bulbs, and in the case of onions, bulbs in the big business sense. I'll bet >there are plenty of studies which have determined precisely when those bulbs >need fertilization and just what nutrients they need when. >....... >Jim McKenney ************************************************* 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