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The need to find alternatives to synthetic herbicides has led to the evaluation of the use of allelopathic biomass from different agroforestry species as soil amendments for weed control. Mentha suaveolens Ehrh. (apple mint) could be a suitable candidate as an ecoherbicide due to its availability in the agroecosystem, well-studied biological activities, and known chemical composition. For the present study, two greenhouse pot experiments were conducted by incorporating flowering aerial biomass of apple mint into the soil. In the first one, the potential phytotoxic effects of M. suaveolens at doses 1 and 2% were evaluated on the germination and growth of maize and its accompanying weeds. In a second temporary assay, the duration of phytotoxicity and the effects of apple mint (0.5% dose) on the physicochemical properties of the soil were elucidated. The soluble (phenolics and organic acids) and volatile compounds potentially releasable from the allelopathic biomass were identified. The apple mint exerted adverse effects on the germination and growth of dicotyledonous weed species, especially Amaranthus retroflexus and Solanum nigrum, with almost 100% inhibition, as well as on the growth of monocotyledonous weeds such as Digitaria sanguinalis, with a reduction of more than 95%. On the contrary, maize yield and soil properties pH, CECe, organic matter, and exchangeable cations were improved by the ecoherbicide. Chemical analyses of apple mint aerial biomass revealed the presence of 7 phenolic compounds, 9 organic acids, and 32 volatiles. For this study, the effects of incorporating M. suaveolens aerial biomass into soil were evaluated for the first time, and it was demonstrated that it has potential as an eco-friendly plant-based tool for Integrated Weed Management.

The need to find alternatives to synthetic herbicides has led to the evaluation of the use of allelopathic biomass from different agroforestry species as soil amendments for weed control. Mentha suaveolens Ehrh. (apple mint) could be a suitable candidate as an ecoherbicide due to its availability in the agroecosystem, well-studied biological activities, and known chemical composition. For the present study, two greenhouse pot experiments were conducted by incorporating flowering aerial biomass of apple mint into the soil. In the first one, the potential phytotoxic effects of M. suaveolens at doses 1 and 2% were evaluated on the germination and growth of maize and its accompanying weeds. In a second temporary assay, the duration of phytotoxicity and the effects of apple mint (0.5% dose) on the physicochemical properties of the soil were elucidated. The soluble (phenolics and organic acids) and volatile compounds potentially releasable from the allelopathic biomass were identified. The apple mint exerted adverse effects on the germination and growth of dicotyledonous weed species, especially Amaranthus retroflexus and Solanum nigrum, with almost 100% inhibition, as well as on the growth of monocotyledonous weeds such as Digitaria sanguinalis, with a reduction of more than 95%. On the contrary, maize yield and soil properties pH, CECe, organic matter, and exchangeable cations were improved by the ecoherbicide. Chemical analyses of apple mint aerial biomass revealed the presence of 7 phenolic compounds, 9 organic acids, and 32 volatiles. For this study, the effects of incorporating M. suaveolens aerial biomass into soil were evaluated for the first time, and it was demonstrated that it has potential as an eco-friendly plant-based tool for Integrated Weed Management.

In our previous studies, the phytotoxicity of Ulex europaeus (gorse) and Cytisus scoparius (Scotch broom) was demonstrated in vitro and argued to be caused by the release of volatile and water-soluble compounds from fresh plant foliage. In light of these positive results, there was a need to test the effects ex vitro. In this work, gorse and Scotch broom were used as soil amendments in pot experiments in a glasshouse by incorporating slashed plant material into the soil at a ratio of 1% w/w on a dry mass basis. The phytotoxic effects on the emergence and early growth of maize and five accompanying weed species were analyzed, as were the effect on soil fertility and soil community-level physiological profiles. Thirty days after incorporation, significant decreases in weed density of 32.2% and 59.5% were found for gorse and Scotch broom soil amendments, respectively. Gorse soil amendment was notably effective impairing the establishment of Amaranthus retroflexus and diminishing the plant height of Digitaria sanguinalis and Portulaca oleracea. Scotch broom soil amendment was capable of significantly inhibiting the emergence of D. sanguinalis, Convolvulus arvensis, P. oleracea, and A. retroflexus, with a notable reduction of weed biomass. No undesirable side effects on maize crop or soil quality, including microbial activity, were detected. Our results suggest that the incorporation of gorse and Scotch broom foliage is promising for pre-emergent weed control in maize; however, field trials that support and expand these glasshouse results are essential

Eucalyptus globulus Labill. (Tasmanian blue gum), one of the most widespread wood species, is broadly grown in forestry exploitations for timber production, giving rise to abundant harvest residues devoted to obtaining bioenergy or essential oils. However, considering the need for searching new environmentally friendly strategies for weed control, a question arises: ‘would remnants of pruning and logging from eucalyptus plantations be processed and used as a green manure with herbicidal potential in agricultural fields?’ After the evident allelopathic nature of E. globulus and the phytotoxic effects observed from our previous in vitro and greenhouse studies, it is time to address the actual ability of eucalyptus residues for weed control under field conditions. In this study, the potential of E. globulus leaves for weed control was approached by field experiments conducted in weed-infested maize fields, during two growing seasons and at two different locations. Significant reductions were observed on the biomass of the dominant problematic weed species Digitaria sanguinalis (L.) Scop. and Chenopodium album L. up to 69.5 and 88.5% relative to control plots, respectively, together with general effectiveness for weed control throughout the experiments. Concomitantly, maize was not negatively affected by eucalyptus green manure. The phytotoxic effects on weeds were more significant at early stages of maize establishment since weed biomass was reduced from ca. 38–80% relative to control plots, thus alleviating weed-crop competition. Additionally, eucalyptus green manure increased pH, CECe, exchangeable cations Ca, Mg, and K , and microbial biomass carbon, as symptoms of enhanced soil quality. Our results demonstrate that the incorporation of E. globulus harvest residues into the soil as a green manure can be a feasible and environmentally friendly practice for field weed control in organic maize-based cropping systems.