Winter cover crops and dynamics of weeds in agricultural systems of the Argentine Rolling Pampas

Abstract The aim of this study was to determine if different mixtures and monocultures of cover crops (CC) reduce aerial dry matter, number and diversity of autumn-winter weeds. Two experiments with different CC species were implanted in the INTA Pergamino Agricultural Experimental Station (Pergamino, Buenos Aires, Argentina, 33° 51´ S, 60° 34´W) in 2018 and 2019. The species used were: Avena sativa, Triticosecale and Vicia villosa. Mixtures and monocultures of CC were used, in different proportions and densities, and were compared with a chemical fallow. Two cuts of CC were made aboveground at tillering and milk grain stages (Z 2.5 and 7.3, respectively) to obtain aerial dry matter of CC (ADMcc, g.m−2), ADM of weeds (ADMw, g.m−2) and number of weeds (weeds.m−2). Moreover, weed species were identified and Shannon diversity and evenness indices and effective specific richness were calculated. In 2018, the highest ADMcc was recorded in Avena sativa at Z 2.5 as well as the highest weed density. At Z 7.3, the highest ADMcc was recorded in Avena sativa, Triticosecale and their mixture. At that stage, the highest ADMw was recorded in the chemical fallow. In 2019, the 3:1 Avena sativa/Vicia villosa mixture showed the highest ADMcc and diversity of weed community showed non-significant differences from the chemical fallow at Z 2.5. There were non-significant differences in ADM among CC and diversity of weed community in the CC was practically null at Z 7.3. At both stages, the highest number of weeds and ADMw was observed at chemical fallow, whereas in CC, non-significant differences were detected. The results obtained indicate that CC reduce the number, ADMw and diversity of the weed community, regardless of the mixtures used.