Effects of Intercropping on Weeds Control and Dragon’s Head (Lallemantia iberica Fischer & C.A. Meyer) Yield

Intercropping is one of the most common practices used in sustainable agricultural systems which have an important role in increasing the productivity and stability of yield in order to improve resource utilization and environmental factors. Intercropping is an option for reducing weed problems through non-chemical methods. Dragon’s head (Lallemantia iberica Fish. et Mey.) is an annual herb from the Lamiaceae family. This plant mainly cultivated for its grains that contain about 30% (even 35-38%) siccative oil with iodine value between 163 and 203, which is used in foods, but especially in dye and varnish industry. Despite the positive effects of intercropping on weed control and the increment in crop yield and the very important role of dragon’s head in sustainable agriculture in arid and semi-arid regions of Iran, information on the effects of these factors on this medicinal plant is scarce. Therefore, in this research, the effect of cumin-dragon’s head additive intercropping in the improvement of the dragon’s head yield and weed control was investigated.

To evaluate the effect of cumin and dragon’s head additive intercropping on weed control and yield of dragon’s head, a factorial experiment based on a randomized complete block design with three replications was carried out at the Research Farm of the Faculty of Agriculture, University of Tabriz, Iran in 2014. Treatments were two levels of weed control (complete control and no weed control) and sole cropping of two crops as well as three additive intercropping ratios including of 100% cumin + 20% dragon’s head, 100% cumin + 40% dragon’s head, 100% cumin + 60% dragon’s head. At the maturity time, plants of 1 m2 in the middle part of each plot were harvested and biological yield, grain yield per unit area as well as harvest index of dragon’s head were determined. Land equivalent ratio (LER) and relative value total (RVT) were used to quantify the efficiency of the intercropping treatments.Data were analyzed by MSTAT-C requires and SPSS 16 softwares and the means were compared using Duncan multiple range tests at p ≤ 0.05. Excel software was used to draw figures.

The effect of planting pattern was significant on the dry weight of weeds. Intercropping of 100% cumin + 20% dragon’s head had the lowest weed biomass. The highest biological and grain yields of dragon’s head under weedy and weed-free conditions were obtained from the monoculture of the dragon’s head. However, among different intercropping treatments, the highest biological and grain yields of dragon’s head were related to 100% cumin + 60% dragon’s head in both conditions of weed treatment. The maximum harvest index was also recorded for monoculture of dragon’s head under weed-free conditions. The land equivalent ratio was more than 1 in intercropping patterns (LER>1) that shows the positive effect of intercropping on yield. Although weed biomass in 100% cumin + 60% dragon’s was higher than that other planting patterns, the maximum LER (1.42) based on seed yield were observed in this planting system under weedy condition. In weed-free conditions, increasing of dragon’s head density reduced LER, while in the weedy conditions, the increment in dragon’s head density was associated with improved LER, indicating the higher efficiency of intercropping of these two plants under no weed control conditions.

The results of this research showed that the combination of 100% cumin + 60% dragon’s head, especially under weedy condition, was the superior treatment, because of the highest land equivalent ratio (1.42). In general, intercropping of cumin and dragon’s head, especially 100% cumin + 60% dragon’s head, is recommended for the creation of variety and production stability and increasing land-use efficiency under weedy condition.