A pot experiment was carried out throughout two successive seasons (2002/03 and 2003/04) at Antoniades Research Branch, Hort. Res. Inst. Alex., Egypt to evaluate the effect of applying organic manure and KristalonTM mineral fertilizer (19:19:19 of NPK) in presence or absence of biofertilizers of Nitrobein (Azotobacter chroococcum and Azospirillum barasilense) and Phosphorein (containing phosphate dissolving bacteria) on bulbs production of Narcissus tazetta, L. grown in sandy loam soil. The mineral fertilizer was added at three rates (1.0, 2.0 or 3.0 g/ pot/month) four times during the growing season. Organic manure was added to the soil before planting at three rates of 6.0, 12.0 or 18.0 g/ pot. The biofertilizers were added at the rate of 10 g/ pot.
The results indicated, generally, that all biofertilizer treatment significantly increased most of the studied leaf characteristics, bulb circumference, fresh and dry weights of bulbs, root dry weight, bulbs uptake of N and P and the available of these elements in the sandy loam soil.
It was noticed that the interaction effect of applying biofertilizers with gradual amounts of mineral fertilizer resulted in significant gradual increases in most of the studied characteristics. The same trend of results was observed as a result of applying gradual rates of organic manure combined with mineral fertilizer.
The interaction effect between biofertilizers inoculation in the soil amended with organic manure with increasing mineral fertilizer rates caused a gradual significant increase in leaf characteristics, the produced bulb characteristics and bulbs uptake of N and P and the available of these elements in the sandy loam soil. The best results were obtained with application of organic manure and mineral fertilizer at rates of 18 g and 3 g per pot, respectively in the presence of biofertilizer, which increased all leaf and bulbs characteristics, roots dry weight, the uptake of N, P and K of bulbs. As well as, significant increasing was detected on the availability of N, P and K in sandy loamsoil. The study recommends that application of organic manure at the rate of 18 g/pot with 3 g/pot of mineral fertilizer and inoculation with biofertilizers is the best treatment for producing high quality narcissus bulbs in sandy loam soil and obtaining suitable levels of available of N, P and K in the soil.