Interaction Between Maize, Intercrops and Weeds in Continuing Relay Cropping System

Continuous cropping leads to declines in soil productivity, 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, 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). Poaceae intercrops germinated faster and competed effectively with weeds, particularly rye, oat, and later ryegrass, which was the most productive (200 g m^-2 ADM). Brassicaceae intercrops also developed rapidly, especially mustard, Camelina and radish (the most productive 206 g m^-2 ADM). Most of the intercrops competed with maize, reducing its productivity, but weeds competition was higher. 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 was the most productive, effective in suppressing weeds and less competitive with maize (CEI 4.82).