Abstract
The phytotoxic relationships between crops and weeds can cover a role in weed management, reducing the use of chemical herbicides. Starting from the organic farmers’ experience, the study aimed to define the inhibitory action of Lolium multiflorum Lam., used as a cover crop before rice sowing, against Echinochloa oryzoides (Ard.) Fritsch, one of the main rice weeds. In vitro 7-day assays were carried out in Petri dishes to compare the effect of different L. multiflorum Lam. parts, in the form of aqueous extract or powder, on the seed germination and seedling growth of Oryza sativa L. and E. oryzoides and to verify the hypothesis of a higher susceptibility of the weed. The total polyphenolic content, as the potential source of allelochemicals, in the L. multiflorum parts was measured. The results showed that both species suffer the phytotoxic action of L. multiflorum, but a more marked effect against E. oryzoides was recorded. In according with the polyphenol quantities, stem and inflorescence extracts showed the more significant species-specific inhibition. In all assays, the weed showed a stronger reduction in the root length and seedling vigor index, and, in some cases, also in the germination percentage and shoot length compared to rice.
Highlights
Weeds cause severe crop losses in rice production worldwide
The impact of the L. multiflorum biomass aqueous extracts and its powder was assessed versus the germination and seedling growth of both E. oryzoides and O. sativa to highlight a potential species-specific action of L. multiflorum
The obtained data showed a significant impact of the L. multiflorum stem aqueous extract on all the considered indices, except for the mean germination time (MGT), in both target species, but with a more evident effect against E. oryzoides than O. sativa
Summary
Weeds cause severe crop losses in rice production worldwide. The yield reductions in flooded paddy fields are due to the presence of invasive aquatic and semi-aquatic species. Weed control in organic farming is carried out through crop rotation and the use of cover crops, smother crops and green mulching, which are important for regulating the weed seed population in the soil and the plant population in the field [16,17]. In this regard, several factors influence the weed growth such as competition for space, water and nutrients, changes in temperature and shade as well as toxic microbial products, soil pH and release of allelochemicals [18]. The impact of the L. multiflorum biomass aqueous extracts and its powder was assessed versus the germination and seedling growth of both E. oryzoides and O. sativa to highlight a potential species-specific action of L. multiflorum
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