Trait-based cropping of brassicaceous plants: Effects on ecosystem services and crop yield

Abstract

Diversification of agroecosystems through mixed cropping can facilitate multiple ecosystem services that may improve yields. Intercrops may repel pests and nourish natural enemies while trap crops lure pests away from target crops. A small-scale agricultural field experiment was conducted in 2018 and 2020 in Finland to study how intercropping of brassicaceous plants and faba bean (Vicia faba) affects yield and quality of a target crop (white cabbage (Brassica oleracea var. capitata)), herbivory on the target crop, and effects of the insect communities linked to the observations. The study was conducted with five different plot arrangements in each year. Broccoli (Brassica oleracea var. italica) or turnip (Brassica rapa var. rapa) were located at the perimeters of 6 × 6 m plots as trap crops. They were planted either alone or with yellow rocket (Barbarea sp). Faba bean was planted as an intercrop in the most complex designs. Cabbage head fresh weight was greatest in the most complex plot type, which included cabbage, broccoli, yellow rocket and faba bean and the head weight was significantly greater than in the cabbage monocrop or the plots with a broccoli-only trap crop. Turnip was included in the experiment in 2020 and efficiently attracted flea beetles and pollen beetles. In 2020, the turnip trap crop alone and the most complicated designs with broccoli or turnip combined with yellow rocket and faba bean significantly reduced P. xylostella abundance in the middle of the plot. Possibilities to use trait-based cropping systems in white cabbage production are discussed.