Investigation of thermal requirement, growth and yield characteristics of two species of Persian shallot (Allium altissimum and A. hertifulium) in different density, bulb weight and flowering stem removing

Persian shallot is one of the important medicinal and industrial plants in Iran which is under very dense utilization. Study of morphological characteristics of Persian shallot in agronomical systems is very important for expanding agronomic production. In order to evaluate some physiological and yield characteristics, and thermal requirement of two species of shallot, a field experiment was conducted at Research Field of Fersowsi University of Mashhad, Iran in 2012-2013. The experimental treatments consisted of two Persian shallot (Allium altissimum from Khorasan and A. hertifulim from Lorestan), two groups of bulb weight 10-20 and 20-30 g), with three plant densities (10, 20 and 30 plants.m-2). A factorial experiment based on completely randomized block design with three replications was conducted. The results showed that in all phonological and yield characteristics, A. hertifulium was significantly weaker than A. altissimum. Leaf area and shoot dry weight in different plant densities and bulb weight in A. hertifulium were significantly lower than A. altissimum. The results also indicated that thermal requirement of A. hertifulium was less than the other species. Growth duration in A. hertifulium was 239 days with 1664 growing degree days (GDD) whereas A. altissimum needed 252 days with 2000 GDD. Plant density of 30 plant.m-2 caused a significant reduction in yield and bulb weight of A. altissimum but the number of bulb.m-2 was increased significantly. Same results were shown in A. hertifulium up to 20 plant.m-2. Removing flowering stem treatment had significant effect on yield characteristics in both species. Removing flowering stem caused accumulation of more dry and fresh weight, diameter and volume in harvested bulbs compared to control.