Effects of Intercropped Insectary Plants (Sweet Alyssum, Coriander, and White Mustard) on Elemental Composition and Antioxidant Levels in Broad Bean Plants

Insectary plants, such as sweet alyssum, coriander, and white mustard, are well known for their traits that attract beneficial insects, allowing them to protect crops from pests. The aim of the study was to analyze the compounds that are important in the antioxidant response, such as malondialdehyde, ascorbic acid, proline, total phenolics, and total flavonoids, as well as the content of elements, including macroelements (K, Mg, Na, Ca, P, and S) and heavy metals (Cd, Cu, Zn, Pb, Ni, Mn, and Fe) in broad bean plants. These plants were grown in field conditions as the main protected plant alongside a mixture of three insectary plants at different proportions of the individual components. The soil was analyzed in terms of the above-mentioned elements, as well as in terms of its enzymatic activity (arylsulfatase, <i>β</i>-glucosidase, dehydrogenase, FDA (fluorescein diacetate), and acid phosphatase). The introduction of insectary plant mixtures did not cause major changes in the content of the elements in the soil. The changes in the content of elements in broad bean leaves depended on the type of element and the proportion of individual components in the companion plant mixture. However, a general trend of increasing macronutrient content was observed, influenced by the presence of companion plants. All types of companion plant mixtures used enhanced the activity of FDA, while the mixture with 50% sweet alyssum additionally caused an increase in arylsulfatase activity (more than 2 fold). The companion plants improved the physiological condition of the protected plant, which was reflected in the reduced content of proline and total flavonoids. Considering the response of the protected plant to the proposed intercropped plant mixtures and their effect on broad bean growth, it appears that the most suitable mixtures are those with an equal share of all three plant species or a mixture with a predominance of sweet alyssum.