Unravelling the success of weed control by relay intercropping with legumes in low-input cereal-based Mediterranean cropping systems
Creators: name: Leoni, Federico
name: Carlesi, Stefano
name: Kudsk, Per
name: Moonen, Anna-Camilla
Publisher: name: Zenodo
Year: 2022
Subjects: Living mulch
Crop diversification
Integrated Weed Management
Subsidiary crops
Root exudate
Plant interactions
Allelopathy

description: This presentation shows the results of a study investigating the performance of three legumes (Medicago sativa, Medicago polymorpha, and Trifolium subterraneum) as a IPM tool in a relay intercropping system with durum wheat. The study was conducted near Pisa (Italy) in a low-input Mediterranean cropping system for two consecutive wheat-sorghum rotations to assess the effects of relay intercropping of legumes on weeds at crop rotation level. During the intercropping period legumes reduced weed biomass up to 90% compared with the control (wheat sole crop), without negative impact on yield. After wheat harvest, legumes persisted in the field and biomass production level determined their weed control capacity. Medicago sativa and Trifolium subterraneum established a suppressive mulch and reduced weed biomass up to 90 % compared with the control whereas no significant effect was observed for Medicago polymorpha. In the subsequent spring legumes were incorporated into the soil and sorghum was sown. Residual effects of Medicago sativa significantly reduced weeds biomass by the 50% in sorghum compared with the control. Results of this experiment confirmed that the biomass production is a good indicator of the weed control ability of legumes. However, biomass did not fully explain the variability in weed control capacity of the selected legumes. Allelochemical effects of legumes may also be involved. Studying the allelochemical properties of legumes can be difficult under field conditions and therefore two additional laboratory experiments were conducted to deepen the knowledge about the chemical interactions between wheat, legumes, and weeds during two critical phases for weed control: the intercropping period and the period after the incorporation of legume residues into the soil. An intercropping pattern was created in pots to explore the effect of the co-cultivation with wheat on the biosynthesis and root exudation of flavonoids in legumes. Flavonoids with potential allelochemical activity such as daidzein, genistein, medicarpin, formononetin and kaempferol significantly increased in plant tissues and root exudates of the legumes in response to co-cultivation with wheat. An additional pot experiment was carried out to investigate the allelopathic effect of the legume fresh biomass on the germinability of four weed species (Alepecurus myosuroides, Lolium rigidum, Chenopodium album and Sinapis alba). To simulate the incorporation of legumes before the sorghum sowing, legume fresh leaves were grinded and mixed with field soil at two concentrations: 25 and 50 g/l. Results of this experiment were consistent with what had been observed under field conditions and confirmed that Medicago sativa has the highest allelochemical potential compared with the Trifolium subterraneum and Medicago polymorpha. This research was supported by the H2020 project IWMPRAISE (grant number 727321) and FL had a PhD scholarship from Scuola Superiore Sant’Anna in Pisa