Growth and essential oil of peppermint (Mentha piperita L.) plants as influenced by compost and some biostimulants

This investigation was conducted during the two experimental seasons of 2019 and 2020 to explore the impact of compost as organic fertilization and some biostimulants, as well as, their interactions on the plant growth parameters and essential oil of peppermint (Mentha piperita L.) plants. Compost fertilizer was added to the soil of peppermint plants at the levels of 0, 8, 16 and 24/acre Biostimulants were ascorbic acid (Asc) at 50, 100 ppm and yeast extract (YE) at 5 g /l, 10 g /l. The plants were sprayed with these biostimulants as follows: Control (no sprayed plants), Asc at 50, 100 ppm, YE at 5 g /1, 10 g /l, Asc at 50 ppm + 5g /l YE and Asc at 100 ppm + 10 g /l YE. The given results indicated that the application of compost at all levels and also foliar spray with the two examined biostimulants at all concentrations, either single or mixed resulted a significant increase in plant growth traits in terms of plant height, branch number /plant, herb fresh and dry weights /plant, leaves fresh and dry weight / plant, as well as, essential ail %, among the three cuts except for the low level of compost (8 m³/acre) concerning compost levels and, also Asc at s50 ppm regarding biostimulant concentrations, in some cases, as compared to untreated plants. Obviously, treating the plants with compost at the high level (24 m3/acre) registered the highest values of these studied characteristics, among all cuts. Also, foliar spray with the combined treatment (100 ppm Asc + 10 g /l YE) proved to be more effective in augmenting the previous studied traits in all cuts. All tested parameters were significantly affected by the interaction treatments in all cuts. In this concern, most combined treatment significantly augmented all examined aspects in all cuts. Moreover, the addition of compost at the high level (24 m3/acre) plus 100 ppm Asc + 10 g /l YE was the most effective treatment, among all cuts.