Assessment of Different PGPR Formulations as a Biological Fertilizer in Cultivation of Poinsettia (Euphorbia pulcherrima)

Poinsettia (Euphorbia pulcherrima Willd.ex Klotzsch.) is one of the most important potted plants. This research was carried out to determine effects of different PGPR formulations, chemical fertilizers and their combinations on plant growth characteristics and nutrient content of growing medium in two different cultivars (Christmas Feelings and Christmas Eve) of poinsettia. The research was conducted in climate controlled research greenhouse between July 2015 and July 2017. The applications were created as formulation 1 (Paenibacillus polymyxa TV-12E + Pseudomonas putida TV-42A + Pantoea agglomerans RK-79), formulation 2 (Bacillus megaterium TV-91C + Pantoea agglomerans RK-92 + Bacillus subtilis TV-17C), formulation 3 (Bacillus megaterium TV-91C + Pantoea agglomerans RK-92 + Kluyvera cryocrescens TV-113C), formulation 4 (Bacillus megaterium TV-91C + Pantoea agglomerans RK-79 + Bacillus megaterium TV-6D), the full amount of commonly used chemical fertilizer (150 g·100L-1) (100% CF) and by combining the reduced amount of chemical fertilizer by (75 g 100L-1) 50% with each bacterial formulation and control. Some plant growth parameters (the first flower (average number of days between flowering of the first plant) (day), total growing time up to marketable commercial size (average number of days between time for the forming red colour of 50% of bracts leaves and the first plant) (day), main flower stalk length (cm) and main flower stalk diameter (mm), total number of leaves (number plant-1), root collar diameter (mm), fresh weight of plant (g), dry weight of plant (g)) and growing medium characteristics were evaluated in the experiment. In addition to the recommended amount of chemical fertilizer application (100% CF) in poinsettia cultivation, BI and BIII bacterial formulation applications were found positive effects on shortening the time until flowering and early flowering. The poinsettia plants grew shortest time marketable commercial size when supplied with BIII+CF application comparing to control. The bacterial viability in the growth medium ranged from 4.91x106 cfu ml-1 to 1.80x107 cfu ml-1. The maximum total nitrogen (1008.00%) was obtained from BIV application. The highest solvable phosphorus (12.32 ppm) amount was determined in the BIV+CF while the highest potassium (2.02 cmol kg-1) and calcium (8299.03 mg kg-1) amount were found in the BIII application. The poinsettia plants were absorbed sufficient nutrients from the growth medium in CF, BI, BI+CF, BII, BII+CF, BIII, BIII+CF applications and increased in their plant growth and biomass. The