Νarrow Row Spacing and Cover Crops to Suppress Weeds and Improve Sulla (Hedysarum coronarium L.) Biomass Production

Abstract

Sulla (Hedysarum coronarium L.) is a new candidate crop for biofuel production. A field trial was conducted in 2018–2020 in Pyrgos, Greece, and repeated in 2019–2021 to evaluate different row spacings and cover crops for weed management in sulla in a two-factor randomized complete block design (RCBD) with four replications. Four row spacings, namely 76-cm, 51-cm, 38-cm, and 19-cm, were assigned to the main plots. Three cover crops, namely farro wheat (Triticum turgidum subsp. dicoccum (Schrank ex Schübler) Thell.), common vetch (Vicia sativa L.), white mustard (Sinapis alba L.), and an untreated control, were assigned to the subplots. In the first year of sulla growth, weed biomass, sulla stem, and total dry matter yield (DMY) were affected by growing cycles (p-value ≤ 0.05). The 19- and 38-cm row spacings resulted in the lowest weed biomass and the highest stem and total sulla DMY in the first year of sulla growth. White mustard was the most weed-suppressive cover crop in both years and growing cycles followed by farro heat. The highest stem DMY was observed in subplots with white mustard in both years. The combination of 38 cm row spacing and white mustard as a cover crop resulted in the highest cumulative two-year sulla DMY (18.9 t ha−1). Further case studies are needed to evaluate more cultural practices for weed management in sulla and other major biomass crops under different soil and climatic conditions.