Franco Tesio

Allelopathy, a chance for sustainable weed management.

The exploitation of crop allelopathy against weeds may be useful to reduce issues related to the use of herbicides. Several crops, such as alfalfa, barley, black mustard, buckwheat, rice, sorghum, sunflower and wheat, demonstrate strong weed suppression ability, either by exuding allelochemical compounds from living plant parts or from decomposing residues. As well as the positive effect on weed reduction, the introduction in agronomic rotations of allelopathic crops, their use as a mulch to smother crops or as a green manure may also be helpful in reduction of other agricultural problems, such as environmental pollution, use of unsafe products and human health concerns, through a reduction in chemical inputs. Knowledge of allelopathic properties of crops may also be advantageous in mitigation of soil sickness. Moreover, information on weed allelopathy may be profitable in preventing serious crop damage if the weed biomass is buried in the soil, and a crop susceptible to allellochemicals is planned for the following year. The use of allelopathic traits from crops or cultivars with important weed inhibition qualities, together with common weed control strategies, can play an important role in the establishment of sustainable agriculture.

Potential allelopathic effects of Jerusalem artichoke (Helianthus tuberosus) leaf tissues.

Abstract Jerusalem artichoke has been reported to colonize several ecological niches and agronomic crops in southern Europe. This plant is also of interest because of its high biomass production and its potential to produce ethanol for biofuel. Allelopathy may be an advantageous trait in Jerusalem artichoke under cultivation, as it potentially reduces weed interference with the crop, theoretically allowing a reduction of mechanical or chemical input required for weed management. However, this trait may also be unfavorable if other crops are cultivated in rotation with Jerusalem artichoke or in areas infested by this species. The aim of this study was to investigate the sensitivity of selected diverse crops (wheat, lettuce, corn, tomato, rice, and zucchini) and weeds (barnyardgrass, black nightshade, common lambsquarters, common purslane, large crabgrass, and pigweed) to the presence of Jerusalem artichoke dried leaf tissues in laboratory experiments performed under controlled conditions. The simulated soil incorporation of different Jerusalem artichoke residues (four cultivars and a weedy population) was carried out in a series of laboratory and greenhouse experiments. Jerusalem artichoke reduced the radicle growth of seedling lettuce (60%), tomato (30%), large crabgrass (70%), and barnyardgrass (30%), whereas total germination of these species was less affected. Sensitivity to Jerusalem artichoke residues was species dependent; germination and initial growth of corn were not affected, whereas winter wheat, lettuce, tomato, rice, and zucchini seedlings were more sensitive to residue presence. Our experiments show that both wild and cultivated decomposing Jerusalem artichoke residues, particularly leaves and stems, possess phytotoxic potential. Additional field experimentation remains to be conducted to determine if allelopathy in the field contributes to its invasibility. Nomenclature: Jerusalem artichoke, Helianthus tuberosus L.; barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG; black nightshade, Solanum nigrum L. SOLNI; common lambsquarters, Chenopodium album L. CHEAL; common purslane, Portulaca oleracea POROL; corn, Zea mays L.; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; lettuce, Lactuca sativa L.; pea, Pisum sativum L.; redroot pigweed, Amaranthus retroflexus L. AMARE; rice, Oryza sativa L.; tomato, Lycopersicon esculentum Mill.; wheat, Triticum aestivum L.; zucchini, Cucurbita pepo L.

Allelopathic Effects of Helianthus Tuberosus L. on Germination and Seedling Growth of Several Crops and Weeds

ABSTRACT Helianthus tuberosus L. (Jerusalem artichoke) is a perennial herbaceous species which is cultivated for human and animal consumption and sometimes reported as a dangerous weed in several summer crops. Few reports indicate that this species shows allelopathic behaviour. This study, carried out in laboratory and greenhouse conditions, investigated the effects of aqueous extracts from leaf tissues and powdered dried leaves on total seed germination, speed of germination and shoot and radicle elongation of several annual population species. Aqueous extracts were applied at 2.5, 5, 10 and 20%, to seeds in Petri dishes, and powdered dried leaves were applied at 2 t ha−1 to seeds planted in pots. The crops included in the experiments were maize (Zea mays L.), green bean (Phaseolus vulgaris L.), pea (Pisum sativum L.), rice (Oryza sativa L.), tomato (Lycopersicon esculentum Mill.), winter wheat (Triticum aestivum L.), and zucchini (Cucurbita pepo L.). Weed species were Amaranthus retloflexus L., Chenopodium album L., Digitaria sanguinalis (L.) Scop., Echinochloa crus-galli (L.) Beauv., Portulaca oleracea L. and Solanum nigrum L. According to their sensitivity, tested species were grouped into negligibly or poorly sensitive, sensitive to high concentrations and sensitive. Species belonging to the first group were maize, green bean, pea, C. album and P. oleracea. Species sensitive to the highest concentrations were rice, winter wheat, D. sanguinalis and S. nigrum. In the last group, which included tomato, zucchini, A. retroflexus and E. crus-galli, total germination of the last three species was reduced by about 49%, on average. S. nigrum showed no germination at 20% extract concentration. In general, speed of germination was affected more than total germination. In some cases, in particular at low concentrations, a stimulatory effect was recorded.