عنوان مقاله [English]
Background: Peppermint (Mentha piperita L.) is one valuable medicinal plant due to its efficacy in treatment of many diseases and other industries, so increment of quantity and quality of its essence through agricultural techniques has special importance. Excessive use of chemical fertilizers, especially nitrogen, in addition to environmental pollution, infers quality risks for medicinal uses. Intercropping with legumes could be a technique to reduce chemical inputs, especially nitrogen. In addition, it may increase desire of farmers to cultivation of this plant and lead to higher performance, while biodiversity and productivity also increase. So the study was conducted to investigate effects of different levels of nitrogen and transplanting date on some growth traits, yield and essential oil of peppermint in different ratios of intercropping with lentils.
Materials and Methods: This experiment was done as factorial based on a randomized complete block design with three replications during 2015 at research farm of Shahrekord University. Treatments include different ratios of intercropped or sole cropping (66% mint: 33% lentils, 50% mint: 50% lentils, 33% mint: 66% lentils, and sole cropping of peppermint and lentils), three nitrogen levels (100%, 75% and 50% of peppermint request) in two transplanting date for peppermint (29 April and 25 May) were evaluated as first to third factor. Growth characteristics of mint like height, leaf production rate, dry matter yield and grain yield of lentil were measured along with essential oil rate and yield of pepper mint.
Result: Effect of intercropping ratios, nitrogen and transplanting date was significant on growth characteristics, yield and essential oil of peppermint. Higher peppermints were seen in sole cropping, at 29 April and 100% nitrogen requirement, more number of leaves per plant also were in this planting date and nitrogen level in sole cropping. But by reducing of nitrogen fertilizer to 75% and 50%, highest number of leaves were acquired in intercropping treatments especially 66% mint: 33% lentils at 29 April. Intercropping increased dry matter yield, the essential oil rate and yield compare to sole cropping. Conversely, late planting and reduced nitrogen fertilizer decreased these parameters. Intercropping could partly compensate for the lack of nitrogen and planting date. In 29 April, dry matter yield of 66% mint: 33% lentils at all levels of nitrogen fertilizer was higher than sole cropping. The highest yield of grain (2614 kg per hectare) also was obtained in its sole cropping, this means that lentil was not dominated in this intercropping system. Total land equivalent ratio for 75% N fertilizer was mar than one in all intercropping ratios, tough in first transplanting date plots with 50%mint:50%lentil and for second transplanting date 66%mint:33%lentil with 1.17 and 1.1 had higher LER.
Conclusion: Since late transplanting (25 may) decreased growth parameters of peppermint, transplanting on 29 April is recommended. But in nitrogen deficiency condition, intercropping may yield better results. This result can be related to the nitrogen fixation of lentils. In order to achieve sustainable agriculture, intercropping of these plants recommended.