Effects of ecological agriculture approaches on dragonhead (Dracocephalum moldavica L.) productivity and oil yield

The programmed application of organic fertilizers represents one relevant way to decrease the cost of nitrogen fertilizer, minimizing environmental pollution. We designed the field experiments as a factorial in a randomized complete block design with 20 treatments and three replications at two locations in Iran (Tehran and West Azerbaijan province). The tested treatments were as follows: two genotypes (Landrace and SZK-1 cultivar); seed inoculation treatments (with and without bacterial inoculation), and five fertilization regimes (FR1: 100% urea (70 kg N ha −1 ), FR2: 75% urea (52.5 kg N ha −1 ) + 25% azocompost (3.85 t ha −1 ), FR3: 50% urea (35 kg N ha −1 ) + 50% azocompost (7.77 t ha −1 ), FR4: 25% urea (17.5 kg N ha −1 ) + 75% azocompost (11.55 ton ha −1 ) and FR5: 100% azocompost (15.55 ton ha −1 ). Application of azocompost enhanced total flavonoid content at a high level at Tehran and a medium level at Khoy. High doses of urea enhanced nitrogen accumulation in plants. The treatments with higher azocompost contents reflected the highest amounts of NPK. On the other hand, the Landrace cultivar evidenced higher chlorophyll concentration than the SZK-1 cultivar at Tehran. High doses of urea produced higher photosynthetic pigment in plants. Application of plant growth promoting regulation (at Tehran) and medium concentration of azocompost enhanced xylose concentration. In this context, the azocompost application improved mannose content. The essential oil yield in the Landrace cultivar was higher than that reflected by the SZK-1 cultivar. For both genotypes, results suggest that bacterial inoculation improves essential-oil production. Results showed that plant growth–promoting regulators and azocompost at medium and high levels improved most plant traits. Although the biological-based plant growth promoters exhibited positive effects in some experimental units, these effects were lower than that of a conventional fertilizer regime. Therefore, azocompost integrated with bacterial inoculation responded to be a suitable substitute for chemical fertilizer treatment.