Seedbank reduction after different stale seedbed techniques in organic agricultural systems

Little information is available on the stale seedbed effect on seedbank reduction. This weed management is of increasing interest overall in organic agricultural systems where is no possible to use herbicides. The emergence dynamics and related seedbank reduction were evaluated following adoption of two different stale seedbed techniques (with or without irrigation), made during the spring-summer season in 2001 in organic agricultural systems. As expected, emergence was strongly stimulated by irrigation and soil tillage.When the no-tillage technique was adopted (control), the absence of soil disturbance resulted in extremely low emergence levels, associated with a reduction in the number of the relative species. Consequently, analysis of the residual seedbank of the shallow layer (0- 10 cm) of the control (no-till) showed only small reduction (about 1%). In contrast, the tillage-only experiment led to a reduction of about 5% in the same soil layer. However only with the irrigation, a drastic reduction in the amount of seeds (roughly half) was achieved. In particular, grasses showed the highest seedbank reduction rates. Despite this different effectiveness of the stale seedbed techniques, the soil layers at greater depths (10-20 and 20- 30 cm) were found to be completely unaffected, independently of the agronomic practices carried out. Qualitative analysis of exhumed seeds demonstrated that greatest "forcing of germination" (tillage + irrigation) resulted in a percentage increase of "deep-dormant" seeds as a consequence "non-dormant" seeds decrease. Although stale seedbed appeared to be only partially effective, we believe that if this agrotechnique is properly carried out and repeated at the appropriate times, it promises to be successful in agricultural systems where herbicides are excluded

"Active" Weed Seed Bank: Soil Texture and Seed Weight as Key Factors of Burial-Depth Inhibition

The ability of weeds to survive over time is highly dependent on an ecological strategy that ensures a high level of viable seed remains in the soil. Seed bank persistence occurs because of the specific characteristics of seed dormancy and longevity and the hypoxic microenvironment, which surrounds the buried seeds. These experiments investigate the role of soil texture, burial depth, and seed weight in seed bank dynamics. Seeds of twelve weed species are sown at increasing depths in various soil textures, and emergence data are used to detect the burial depth at which 50% and 95% inhibition is induced, using appropriate regressions. Clay soil is found to increase the depth-mediated inhibition, while it is reduced by sandy particles. In each soil texture, the highest level of inhibition is found for the smallest seeds. Seed weight is found to be closely related to the maximum hypocotyl elongation measured in vitro, and consequently, the seedlings are unable to reach the soil surface beyond a certain depth threshold. However, the threshold of emergence depth is always lower than the potential hypocotyl elongation. The depth-mediated inhibition of buried seeds is even more pronounced in clay soil, highlighting that the small size of clay particles constitutes a greater obstacle during pre-emergence growth. Finally, the role of soil texture and weed seed size are discussed not only in terms of evaluating the layer of “active” seed bank (soil surface thickness capable of giving rise to germination and emergence), but also in terms of developing a consistent and persistent seed bank. Finally, the role of soil texture and weed seed size are discussed, and the layer of “active” seed bank (the soil surface thickness that enables germination and emergence) is assessed with the aim of developing a consistent and persistent seed bank. Assessing seed bank performance when buried under different soil textures can help increase the reliability of the forecast models of emergence dynamics, thus ensuring more rational and sustainable weed management

Weed seedbank biodiversity in emmer wheat (triticum dicoccum (schrank) schübler) in a mountainous agro-ecological oasis (garfagnana, tuscany)

Phytocoenoses of conventional agroecosystems are subjected, already from several decades, to the reduction of the weed species present in the various crops. Such floristic decreasing is directly proportional to intensity of the agronomic impact. The present work is born from the hypothesis that the agro-ecological oases, managed with the ancient agrotechniques, are linked by an high degree of plant biodiversity. In this perspective it was carried out not only an analysis of the field emerged weeds, but even an evaluation of the seedbank since this one synthesizes the weed flora of a wider period. In the experimental agroecosystems, selected due to the typical Emmer wheat presence, an high degree of weed species diversity was observed, above all of terophytes, in the emerged flora as well in the seedbank. In both cases relative densities of each species were found low and without any weed dominance. Probably it occurs as a function of the high degree of competitive and allelopathic interactions. Almost scarce was the presence of exhumed seeds of graminaceae virtually due to their inability to store in the soil a persistent seedbank. Of particular importance it was the discovery of two rare species such as Agrostemma githago and Centaurea cyanus disappeared from many years by the landscape of “conventional” agricultural systems. The seedbank was found uniformly distributed in both sampled soil layers (0-15 and 15-30 cm) confirming that plowing induced an uniform burial of the annually produced seeds. The total examined soil profile (0-30 cm) showed a quantitative seedbank similar to those already found in “biological” agricultural systems (from 12.000 to 47.000 seeds m-2). However it was qualitatively formed even from several weed species of negligible agronomic impact as a function of their scarce competitivity like in the case of some caryophyllaceae (Silene noctiflora and S.alba), boraginaceae (Myosotis arvensis and Echium vulgaris) and campanulaceae (Legousia speculum-veneris). Finally both agronomic and ecological involvements of this weed complexity were discussed. This complexity was retained of crucial importance not only regards to the biodiversity conservation but even for their role in the landscape ecology. In synthesis, it has been confirmed the hypothesis that the ancient phytocoenoses are still present but only in these ecological oases in which the agronomic impact was ecologically sustainable. In conclusion, it was stressed the crucial role of these agro-ecological oases not only with the aim of the in situ biodiversity conservation, but even as ex situ germoplasma source to use in the perspective of ecological restoration of degraded areas

Agronomic, nutraceutical, and organoleptic performances of wild herbs of ethnobotanical tradition

There is a lack of information on how to grow wild herbs as nutraceutical foods. Ten wild herbs were collected in natural and/or anthropized environments and assessed for their agronomic performance as fresh-cut (or ready-to-eat) leafy vegetables and their nutraceutical and organoleptic attributes. Seed dormancy prevented acceptable germination in many species. However, a physiological seed treatment (soaking with sodium hypochlorite followed by incubation for 3 mo at 4°C in sand moistened with potassium nitrate solution) allowed satisfactory germination, usually above 80%. Cultivation in alveolar containers produced highly diversified fresh-cut productivity (250-550 g·m-2), lower than that of lettuce (Lactuca sativa L.; 16 >900 g·m-2) grown as a reference fresh cut green vegetable. Antioxidant power was often much 17 greater in wild herbs (20.0 to 62.0 mmol Fe2+·kg-1 FW) than in lettuce (21.0 mmol Fe2+·kg-1 18 FW). Evaluation of the sensory profile indicated that softness and sweet taste of lettuce were 19 generally preferred to the more robust flavors of wild herbs. Hardness and bitter taste produced a poor appreciation of most wild herbs. However, exceptions were evidenced due to characteristics of spiciness [Alliaria petiolata (M.Bieb) Cavara & Grande] and/or crunchiness (Silene vulgaris [Moench] Garcke). Frequent distrust for most herbs was expressed as an example of food neofobia that generally occurs for unknown bitter flavors. Most of the wild herbs were not suitable as fresh-cut leafy vegetables, but some species could be ingredients for mixed products with better flavor and health properties

Weeds for weed control: Asteraceae essential oils as natural herbicides.

The aim of this study was to test the botanical family of Asteraceae as a source of natural herbicides. Twenty Asteraceae species were collected during flowering time and evaluated in terms of the yield and quality of essential oils (germination inhibition and growth of weeds). Half the species showed a sufficient yield of essential oil (from about 0.1% to 1.43%) when testing these phytochemicals in vitro as germination inhibitors of two typical weeds, Amaranthus retroflexus and Setaria viridis. Despite the higher tolerance of S. viridis, the concentration of 100 lg L 1 of essential oils of the two Artemisia species and Xanthium strumarium could totally inhibit germination. In addition, at 10 lg L 1, the same essential oils showed full inhibition of A. retroflexus seeds. A comparison of their effectiveness at suboptimal doses led to a further selection of the most promising sources of essential oils. After their chemical characterisation, the essential oils were tested as post-emergence herbicides on seedlings of the above-cited weeds. After spraying the weeds at different concentrations (10, 100 and 1000 mg L 1) during two different phenological stages of weed seedlings (cotyledons and the third true leaf), the essential oils of Artemisia annua and X. strumarium showed the best performance. The essential oils of X. strumarium were then tested again on both weeds to monitor the dynamics of plant injury. A reduction in plant fresh weight (about 20%–30% after 10 days) and chlorophyll content (destroyed, after the same amount of time) was found, thus confirming the total and rapid effectiveness of these essential oils. In summary, A. annua and X. strumarium have elicited considerable agronomic interest and appear to be suitable as a source of essential oils to act as natural herbicides

Temperature-Associated Effects on Flavonol Content in Field-Grown Phaseolus vulgaris L. Zolfino del Pratomagno

Combining the need to increase local Phaseolus vulgaris L. production, with the objective of identifying which abiotic inductors (irrigation and temperature) and/or elicitors (nitrogen fertilizer treatment) can be used as potential strategies to improve flavonol content, open-field experiments were conducted in Pisa and Bologna (Italy) over two years, using the local landrace of interest \u201cZolfino del Pratomagno\u201d, and a commercial variety, Verdone. Full-irrigation and nitrogen treatment, individually, and in combination, increased yield and decreased flavonols, respectively, in both genotypes and locations. Yield, under all treatments, was significantly higher in Pisa (17.5\u2013 21.9 \ub0C) than Bologna (21.4\u201324.8 \ub0C) for Verdone, but was the equivalent for Zolfino. An inverse correlation between average mean temperature and flavonol content was evident only in Zolfino. The feasibility of increasing dietary flavonol production using decreasing temperature as a strategy with some degree of control was then tested by cultivating Zolfino at different altitudes (108 (24 \ub0C) to 800 m a.s.l. (18 \ub0C)) in Pratomagno. Increasing the altitude induced a significant 3-fold increase in seed-coat kaempferol glycosides, comprising more than 95% of the total flavonols. Temperatureassociated effects on flavonol synthesis warrants consideration when selecting a cultivation environment to augment the kaempferol-based, anticarcinogenic benefits of Zolfino

"Professione" orientatore. L'orientatore universitario quale connettore sistemico

L'articolo prende in considerazione sotto molteplici aspetti il tema dell'orientamento universitario, in particolare le figure dell'orientatore "istituzionale" e "professionale" e il collegamento tra scuola e università