Peppermit was used since 2000 years ago. In the middle ages, in addition to it’s culinary uses, it was used as a medicinal plant to treat bites and stings and as a vulrinary drug.
Regular cultivation of this plant started around 1870 in Japan. Recently, peppermint is cultivated commercially in large scale in different parts of the world.
Peppermint oil has a very high economical value and it’s high quality gives it’s priority to the oil produced by other species of this genus.
This oil due to it’s diffusive pungent odour and cooling effect, in addition to it’s high quality in flavouring foods, soft drinks, tooth pastes, chewing gums, etc, it is used extensively as culinary and medicinal herb overall the world.
Generally said, peppermint essence is used in food and pharmaceutical industries; perfumery and in cosmetic and toilateries industries.
Although, Mentha piperita has a high pharmaceutical importance, no scientific work has been conducted on this plant in Iran.
Due to this fact the effect of N & P fertilizer levels and harvesting management on peppermint growth and production had been conducted in the experimental station of Jahad- Daneshgahi at Karaj, Tehran during 1997.
In this study, four nitrogen fertilizer levels (50, 100, 200 and 300 kgs N/ha), five phosphorus fertilizer levels (00, 50, 100, 150 and 200 Kgs P2O5/ha) and harvesting plants in 3 stage (stage1: the first cut is done when the plants were 15 cm high, stage2: harvesting starts together with the plants of the first stage when the latest reached 15cm high again, stage3: the first cut was done when the plants were in full-bloom stage, the time in which the plants of the other stages were harvested again).
All three experiments were conducted in RCB design separately.
Results can be summarized as follows:
1. Leaves and stems dry matter production and oil production was increased by the increment in nitrogen level. 300 Kgs N/ha was found the best in this experiment.
2. by increasing phosphorus fertilizer level up to 100 Kgs P2O5/ha, dry matter yield of the leaves was significantly increased. However, phosphorus fertilizer level had no effect on stem and herbage dry matter yield.
Oil content was decreased with the increase of fertilizer level. Oil production of leaves and herbage portion of the plants was increased with increasing fertilizer level till 100Kgs P2O5 per hectare.
3. Dry matter yield was decreased with the delay in harvesting stage. The first stage was the best treatment to produce the highest dry leaf yield in this experiment.
Regarding leaf oil content, the third stage was the best treatment but the highest oil yield was achieved by harvesbirg the plants in the first or second stage. A conclusion could be made that peppermint plants harvested in the first stage resulted in highest leaf dry matter and oil yield.
It could be concluded that 300 Kgs N, 100Kgs P2O5 per hectare and harvesting in the first stage were the best treatments in these experiments.