Rotating Intercrops in Continuous Maize Cultivation: Interaction Between Main Crop, Intercrops, and Weeds

Continuous cropping leads to declines in soil productivity and biodiversity, as well as a deterioration of overall phytosanitary conditions. What if we rotate the intercrops instead of the main crops? In a stationary three-year field experiment, maize was intercropped with Fabaceae (faba bean, crimson and Persian clovers, and blue-flowered alfalfa), Poaceae (winter rye, annual ryegrass, spring barley, and common oat), and Brassicaceae (white mustard, spring oilseed rape, oilseed radish, and spring Camelina) intercrops in separate growing seasons. Fabaceae intercrops developed slowly and competed poorly with weeds. The highest air-dried biomass (ADM) was produced by Persian and crimson clovers (approx. 86 g m−2). Intercrops of the Poaceae family, particularly rye and oats, as well as ryegrass, which was the most productive at 200 g m−2 ADM, germinated faster and competed effectively with weeds. Brassicaceae intercrops also developed rapidly, especially mustard, Camelina, and radish (the most productive 206 g m−2 ADM). Most intercrops competed with maize and reduced its biomass productivity; however, their competitive effects were weaker than those of weeds. A strong negative correlation between maize and weed biomass was detected (max. r = −0.946; p < 0.01). Complex evaluation index (CEI) showed that the crimson clover–annual ryegrass–spring oilseed rape rotation (CC-AR-SR) was the most productive and was effective in suppressing major weeds Echinochloa crus-galli, Chenopodium album, Polygonum lapathifolium, and Cirsium arvense, less competitive with maize (CEI 4.82), and can be used as an Integrated Pest Management tool.