1,720,971 research outputs found
A modelling approach for evaluating phenology and adaptation of two congeneric weeds (Bidens Frondosa and Bidens Tripartita)
No full textThe exotic species Bidens frondosa is rapidly spreading in northern Italian arable fields, while Bidens
tripartita, a native congeneric, shows less invasive capacity. To characterise and model the phenology of
the two species, a two-year study was conducted involving sowings at 15-day intervals between March
and August. The length of the sowing-emergence phase was well described by a simple thermal model,
with a base temperature of 4.5 ◦C, for both species. A multiplicative photothermal model was found to be
the best for the emergence-flowering phase. B. frondosa resulted as being less macrothermal and more
sensitive to photoperiod. The flowering-maturity phase lasted for 30–32 days, on average, and was well
described by a model based on soil water availability: this phase shortens when there is a lack of water,
particularly in B. tripartita. The more relevant differences between the two species seem to be related to
the vegetative phase length, which varied from 150 to 46 days and from 123 to 42 days in B. frondosa and
B. tripartita, respectively. Thanks to the high elasticity of its vegetative phase, B. frondosa can grow taller
than B. tripartita and acquire higher competitivity and seed production potential, both relevant factors
in determining the success of a species
Valutazione agronomica e ambientale di diverse strategie di controllo delle infestanti: un approccio modellistico.
No full text
Observations on the potential of microwaves for weed control
No full textField tests of a prototype microwave-based weed killer machine were conducted on Abutilon theophrasti, Panicum miliaceum, lucerne and oilseed rape pure stands. The approach can be considered a thermal weed control method, the microwave radiation causing dielectric heating of plant tissue water that eventually kills the plant. The method could overcome the limitations of other thermal methods, such as fire risk with flaming or the heavy loads required for hot water treatments. Species were effectively controlled by microwave irradiation, but their sensitivity and the evolution of damage symptoms over time differed. Lucerne showed no sigmoidal response and was the least affected by the treatment, while a log-logistic curve expressed the dose–response relationships of the other species quite well. The estimated microwave dose for a 90% dry weight reduction ranged from 1015 kJ m−2 in A. theophrasti to 3433 kJ m−2 in P. miliaceum. Energy cost evaluation indicated that increased efficiency is required for this technique to compete with other thermal methods. Microwave efficiency could be increased by a flux configuration that minimizes soil penetration and maximizes absorption by plants, which, in turn, depends on plant growth form
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