Study on application of some organic matters and drought stress on agronomic traits and yield of lemon balm (Melissa officinalis)

The objective of the current study was to study the effect of drought stress and organic nutrition on quantity and quality of lemon balm (Melissa officinalis). Lemon balm is a perennial herbaceous herb which is extensively used in pharmaceutics and food industries. Given that province of Kerman, Iran, is an arid region, the current study was so important because of the limitation of water resources. The study was carried out in Kerman, Iran in 2008 as a split-plot experiment based on a randomized complete block design with three replications. The main plots included drought stress at two levels of stress and no-stress and the sub-plots included organic fertilization treatments at five levels of three types of green manure (vetch, alfalfa, clover) and decomposed (cattle) manure with the amount of 30 t.ha-1. The drought stress was created by changing irrigation interval. The measured traits included plant height, single-plant leaf number, single-plant stem and leaf dry and fresh weight, single-plant fresh and dry weight, leaf:stem ratio, leaf length and width and finally, leaf area. The data were analyzed and the means were compared by Duncan’s multiple range test. The results showed that the effect of green manures was significant on leaf number, leaf fresh weight, stem fresh weight, leaf dry weight, plant fresh weight and leaf area. Plant yield had the highest correlation with leaf number, plant height, plant fresh weight and stem fresh weight. The highest plant yield was obtained under cattle manure and alfalfa green manure treatment. The effect of drought stress was significant on treatments.