Effect of corm planting density, organic and chemical fertilizers on formation and phosphorus uptake of saffron (Crocus sativus L.) replacement corms during phonological stages

Saffron (Crocus sativus L.) propagates by replacement corms producing from the mother corm after flowering during each season. In order to investigate the effect of corm planting density، organic and chemical fertilizers on formation and phosphorus uptake of saffron replacement corms during phonological stages، a field experiment was conducted as factorial layout based on randomized complete block design with three replications، at Faculty of Agriculture، Ferdowsi University of Mashhad، Iran، during 2013 and 2014 growing seasons. The experimental treatments were all combination of different levels of planting density (25، 50، 75 and 100 corms per m2) and fertilizer sources (manure 25 t. ha-1، chemical fertilizer (N 150 kg ha-1 + P 75 kg ha-1) and control). Due to different sampling dates of replacement corms during phonological stages (21 November، 21 December، 20 January، 20 April and 21 May، respectively)، the experimental data were analyzed as factorial - split in time based on a randomized complete block design. Based on results، the highest number of replacement corms lower than 4 g (5. 8 corms per plant) were observed in fifth sampling stage and then decreased. In all levels of planting density (25 to 100 corms per m2)، the effects of manure on increasing the number، weight and phosphorus content of replacement corms in range of 4. 1 to 8 and 8. 1 to 12 g per plant were significantly higher than chemical fertilizer. In fifth sampling stage، by applying the manure، the weight and phosphorus content of replacement corms in range of 8. 1 to 12 g per plant were significantly increased (approximately twice)، as compared to chemical fertilizer. It seems the decrease in saffron yield as result to decreasing the corm planting density can be slightly offset by increasing the percentage of larger corms formation per plant.