Effect of Leaching on Reducing the Phytoxicity of Some Medicinal Plants on Wheat (Triticum aestivum)

The aim of this study was to investigate the effect of leaching on the reduction of soybean (Glycin max), black cumin (Nigella sativa), dill (Anethum graveolens) and dragonhead (Dracocephalum moldavica) residues allelopathy in wheat (Triticum aestivum) cropping. The experiment was conducted in a completely randomized design with three replications in 2017. The factors consisted of four types of previous plants (soybean, black cumin, dragonhead and dill) and three levels of leaching (without leaching, once leaching and twice leaching). The results showed that the previous plant type and leaching levels had no significant effect on wheat emergence. Leaching reduced the effects of deterioration of soybean, black cumin, dragonhead and dill. The highest rate of emergence was observed with 1.73 seedlings per day for wheat cultivated in soil with dill and dragonhead residues plus once leaching. The greatest root length (24.7 cm) was associated with wheat grown in soils with dragonhead residues plus once leaching. The highest leaf area and chlorophyll a and chlorophyll b content observed in the wheat grown in the soil with soybean residues plus once leaching. It was concluded that in agroecosystems where autumn wheat is in rotation, it is necessary to avoid wheat cultivation in the presence of soybean, black cumin, and dragonhead and dill residues and to reduce the inhibitory effects of these plants, one stage of leaching must be done before the cultivation of wheat.