Sustainable Weed Management.

Weeds are the most important biological constraint determining yield losses for field crops [...].

Differentiated Weed-Suppressive Ability of Modern and Old Durum Wheat Cultivars after Long-Term Cultivation under Semi-Arid Climate.

Durum wheat (Triticum turgidum spp. durum) is one of the most important grain crops cultivated across the Mediterranean Basin, where a strong return to local landraces cultivation is occurring to meet the market demand for high-quality food and low-input cropping systems. A characterisation of the long-term effect (10 years) of durum wheat landraces and modern cultivars on the potential and real weed flora is still lacking. Hence, a multilocation trial over 10 farms in Central-Eastern Sicily was carried out to investigate the repeated cultivation of several old landraces (OLD) and modern cultivars (MOD) on the abundance and diversity of weed flora. Overall, OLD was associated with a 47% reduction of the soil seedbank size and to -64% of the aboveground weed biomass compared to MOD. In addition, diversity indices pointed out a high similarity between MOD and OLD farm groups for the soil seedbank, while a lower diversity was found in OLD for aboveground weed communities. From the principal component analysis emerged that the species compositions of MOD and OLD were quite separated for both soil seedbank and real flora, with the latter showing few specific associations with major weeds. These findings demonstrated the indirect effect of durum wheat landraces in sustainably reducing weed pressure without the adoption of chemical weed control.

Allelopathy in Durum Wheat Landraces as Affected by Genotype and Plant Part.

Durum wheat is one of the largest cultivated crops across Mediterranean areas. The high demand for sustainable crop productions, especially concerning weed management, is driving the return to local landraces. In the present work, the in vitro allelopathic effects of the extracts of three durum wheat landraces ('Timilia', 'Russello' and 'Perciasacchi') and a modern variety ('Mongibello'), obtained from three different plant parts (ears, stems and roots), were tested on seed germination (G) and mean germination time (MGT) of Portulaca oleracea L. and Stellaria. media (L.) Vill., two weeds commonly infesting wheat fields. In addition, the total polyphenol (TPC) and total flavonoid (TFC) content of extracts was determined. All extracts reduced G and increased MGT in both weeds compared to the control. The magnitude of phytotoxicity was strongly affected by the influence of genotype, plant part and extract dilution. Overall, the landraces 'Timilia' and 'Russello' showed the highest allelopathic effects, ear extracts were the most active, and the maximum extract dilution induced higher phytotoxicity. Extracts' TPC and TFC corroborated these results. The findings obtained here encourage the use of local landraces as a source of allelochemicals and suggest that they could be left on soil surface or soil-incorporated after harvest for a possible weed control.

Trifolium subterraneum cover cropping for improving the nutritional status of a Mediterranean apricot orchard.

BACKGROUND: The utilization of Trifolium subterraneum L. cover crops may represent an innovative and efficient option in low-input and organic farming, especially in Mediterranean agroecosystems where low and irregular rainfall require frequent soil tillage and use of herbicides to reduce moisture losses and weed competitiveness. Since imbalances of soil macro- and micro-nutrients due to cover cropping establishment could be responsible for numerous problems in specialized orchards, such as disturbances in the normal tree growth and quality of fruits, the objective of this study was to investigate, the cumulative effects of a 3-years established T. subterraneum cover cropping, compared with a spontaneous flora and a conventional management (as a control), on the levels of mineral nutrients in the apricot leaves and fruits. RESULTS: Our findings indicated that T. subterraneum cover cropping tended to stimulate higher leaf macro- and micro-nutrients content than conventional management and flora spontaneous cover cropping. In addition, the presence of T. subterraneum cover cropping, especially with the incorporation of dead mulches into the soil, increased the content of potassium (K), nitrogen (N), calcium (Ca), iron (Fe) and manganese (Mn) in apricot fruits. CONCLUSION: Taking also into account the effects of T. subterraneum cover cropping on both the reduction of soil weed and enhancement of bacteria communities involved in the soil N-cycle, we may suggest its application in Mediterranean orchards as an eco-friendly alternative to synthetic herbicides for weed control and mineral N fertilizers, while enhancing the apricot tree nutritional status and fruit quality. © 2020 Society of Chemical Industry.

Long-Term Effect of Cover Crops on Species Abundance and Diversity of Weed Flora.

Cover crops are gaining in popularity as an eco-friendly tool for weed control in organic and low-input agricultural systems. A 5-year study was carried out in a Mediterranean environment (Sicily, south Italy) to (1) quantify cover crop biomass production and (2) evaluate the effects on weed soil seed bank, aboveground biomass, species richness, species composition and associations between communities. Cover crop treatments included subterranean clover (Trifolium subterraneum L.) and spontaneous flora, both with and without burying dead mulch into the soil, compared to a conventional management treatment. Weed biomass was significantly reduced by subterranean clover, contrariwise to spontaneous flora, with season-dependent results. Cover crop biomass, which ranged from 44 to more than 290 g DW m-2, was negatively correlated to weed biomass. Moreover, subterranean clover decreased the size of the soil seed bank and species richness. Based on relative frequency, a low similarity was found between the conventional management and cover crop treatments. In addition, no significant differences in species composition across treatments were observed, whereas principal component analysis highlighted some associations. The results suggest that subterranean clover cover cropping is a good option for weed management in Mediterranean agroecosystems.

Temperature and storage time strongly affect the germination success of perennial Euphorbia species in Mediterranean regions.

This study aims to explore the effect of environmental factors (temperature, light, storage time) on germination response and dormancy patterns in eight Mediterranean native wildplants, belonging to the Euphorbia L. genus. In detail, we considered E. amygdaloides subsp. arbuscula, E. bivonae subsp. bivonae, E. ceratocarpa, E. characias, E. dendroides, E. melapetala, E. myrsinites, and E. rigida. We collected seeds from natural plant populations and performed germination assays in climatic chambers at seven constant temperatures (from 5 to 35°C, with 5°C increments), and four fluctuating temperature regimes (8/15, 8/20, 8/25, and 8/30°C, with a 12/12 hr thermoperiod). Germination assays were set up both in dark (D) and in light/dark conditions (L/D, 12/12 hr photoperiod), after short and long seed storage (SS around 30 days and LS around 150 days). For all these species, except E. amygdaloides subsp. arbuscula, results show that the final germinated proportions were improved by a long storage period (>150 days), which supports the existence of nondeep physiological dormancy. Optimal temperature levels ranged from 14.3 to 21.3°C and base temperatures ranged from 5.6 to 12.1°C, while ceiling temperatures from 25.6 to 34.7°C. For none of these species, germinations were favored by an alternating daily temperature regime, while in several instances, germinations were quicker and more complete in darkness, than in an alternating light/dark regime. In some instances, extreme temperature levels (5 and 30°C) induced dormancy and germinations did not resume when seeds were exposed at optimal temperature levels. Results are discussed in terms of the dynamics of emergences and how this might be affected by climate changes.