1,721,091 research outputs found
Rule-based Handling of Hazardous Nitrogen
Full text linkA rule-based, recursive framework is an ideal approach to support the design of cropping systems (CS). A framework of this type was proposed, arranged into three stages (Silvestri and Bellocchi, 2007): (phase I) prior evaluation (technical, problem-solving, farmer-driven stage), (phase II) posterior evaluation (institutional, environmental monitoring implemented when CS response deviates from expected behaviour), and (phase III) managing the change (participatory, dynamic rearrangement of CS). This sequence is meant to evolve and grow over time through reiterations (Fig. 1), allowing for a continuous adaptation of agricultural productions systems as the business environment and society change. The same procedure was applied in this study to assess the behaviour of an array of CS run in the proximity of Lake Massaciuccoli - an area of Central Italy currently defined as “vulnerable area” under EU Directive 676/91 - as part of an action aimed at identifying possible responsibilities of farmers in NO3 contamination of waters (research developed in 2005-2006 under the Italian Ministry of Education, University and Research)
Modeling and upscaling plot-scale soil erosion under mediterranean climate variability
No full textSoil erosion is an issue in the Mediterranean slopes. Erosion plots are useful to quantify erosion rates, but data are difficult to scale up to a slope level. Moreover, short observational frameworks are generally established, making it difficult to represent multi-year fluctuations. This paper deals with the potential of parsimonious modelling to upscale plot erosion (~23 m2) at Monte Pino Met European Research Observatory (South Italy) from 2001 to 2006. Under the assumption that the slope is fractal and contains plots, monthly gross soil erosion was modeled by lumping together the erosivity factor (runoff component), Normalized Difference Vegetation Index (vegetation cover factor), and the spatial scale dependence (slope length factor). This model was applied to reconstruct monthly gross soil erosion rates for the period of 1986–2006, for which hydrological inputs were available with sufficient detail. Pronounced interannual variations, with two distinct patterns, were observed: increasing rates of erosion were visible in 1995–2006 (peaking in November 1997, 50 Mg·ha−1·month−1), while in previous years only a few peaks slightly exceeded the average of the whole period (1 Mg·ha−1·month−1). Hydrological conditions indicate that important erosional processes have been triggered during low-frequency, short rainfall events occurring in spring–summer (e.g., May 2001, June 2003), or during longer, less intense events occurring in autumn–winter (e.g., November 1997) seasons. It is likely that increased precipitation amounts associated with more frequent convective storms created conditions for higher energy events triggering erosion. For the recent warm period, investigations at a higher than monthly resolution are required to better assess the seasonal changes of erosion rates and their relationship with soil conservation
Effect of light quality on somatic embryogenesis of quince leaves
No full textThe effect of light quality on somatic embryogenesis in quince BA 29 was investigated. 2,4-D induced leaves were exposed for 25 days to the following light quality treatments: dark, far-red, far-red+blue, far-red+red, blue, white, red+blue, red. After a further 20 days of white light exposure, somatic embryo production was recorded. Somatic embryogenesis was highest in cultures subjected to red light treatment, and decreased progressively with the transition to red+blue and to white. Overall, embryogenic competence showed a correlation with photoequilibrium. Phytochrome appeared to be inductive although this effect was adversely influenced by the blue absorbing photoreceptor, in particular at low photoequilibrium. Independently of light treatments applied, somatic embryos frequently showed severe morphological abnormalities. Conversion of somatic embryos to plantlets was not observed
Effect of long-term in vitro shoot culture on somatic embryogenesis of quince leaves treated with different light qualities
No full textThe effect of long-term in vitro shoot culture on somatic embryogenesis in quince BA 29 was investigated. Three experiments were performed on leaves explanted at about 8-mo. intervals from the same culture stock and maintained under different light qualities. Embryo production was assessed either in terms of percentage of embryogenic leaves or number of embryos per leaf. By appropriate data processing both these responses were linearly related to photoequilibrium in each experiment. Statistical comparisons among the three experiments showed significant differences both in mean (computed over light qualities) and line slope values. In particular, with increasing shoot culture age, both percentage of embryogenic leaves and number of embryos per leaf progressively increased, while mean slope values decreased. The increase in mean values suggests a positive effect on somatic embryogenesis due to possible tissue rejuvenation when mother cultures were cultivated in vitro for longer periods. Slope decrease over time indicated the interactions between age of the in vitro culture and photoequilibrium. Thus, embryo production at different culture ages was consistently found to be highest at high photoequilibrium values; in contrast, if a low level of phytochrome was activated, embryogenesis in the youngest cultures was low or absent, but increased with the progressive tissue rejuvenation arising from long-term in vitro culture
Influenza della concimazione azotata sulla intercettazione della radiazione del mais (Zea mays L.)
No full textResistenza agli insetticidi in popolazioni di Bemisia tabaci (Gennadius) provenienti da coltivazioni in serra
No full textEffect of 2,4-D and light quality on callus production and differentiation from in vitro cultured quince leaves
No full textThe effects of 2,4-dichlorophenoxyacetic acid (2,4-D) concentration, length of induction period and light quality on leaf regeneration of quince clone BA 29 were investigated. After 2, 4 or 6 days of induction with 2.5 mg l-1 or 5.0 mg l-1 2,4-D, leaves were cultured under red, blue, red+blue, far-red+blue, white, far-red light or darkness conditions. Leaves thereby treated showed different responses, with respect to somatic embryogenesis, callus, rednodular structures or roots. Callus production increased with increasing 2,4-D concentration and induction period, although it was not influenced by light quality; the only exception was far-red+blue light, which reduced callusing response. This result suggested involvement of the blue-absorbing photoreceptor system in the callus formation processes. A high regeneration of red-nodular structures with a meristematic appearance was also observed; from some histological characterizations, we presumed they were adventitious buds that were arrested at an early developmental stage. Red-nodular structures increased with decreasing 2,4-D concentration and induction period. In the regeneration of such structures, the blue-absorbing photoreceptor system appeared to have a negative effect but only at a low photoequilibrium value. In contrast, light quality which activated phytochrome induced an increment in regeneration, but the response did not vary for photoequilibrium values ranging from 0.43 to 0.86. For root regeneration, phytochrome seemed to be the only photoreceptor involved
Possibilità e limiti dell’uso degli indicatori nella valutazione agro-ambientale dei sistemi colturali
No full textNegli ultimi decenni sono stati sviluppati diversi strumenti speculativi per lo studio dei sistemi colturali e fra questi un crescente interesse ha suscitato l’impiego degli indicatori. Nel presente lavoro si illustrano i principi teorici che stanno alla base di un loro corretto utilizzo ed in particolare si mettono in evidenza le potenzialità ed i limiti che la loro applicazione pone nella valutazione agronomica ed ambientale dell’esercizio dell’attività agricola.
I punti critici da affrontare sono riconducibili all’individuazione ed alla definizione del tipo di relazione che lega l’indicatore e l’entità indagata, alle modalità di aggregazione e di ponderazione degli indicatori al fine di accrescerne le potenzialità descrittive, all’attribuzione di opportune funzioni di valore ed alla comparabilità delle indicazioni ottenute dalla loro applicazione in tempi ed in luoghi diversi.
L’aspetto forse più delicato rimane però quello dalla scelta degli indicatori da utilizzare, in quanto il superamento di tale fase non si dimostra neutra, né per quel che concerne la composizione di un ordine di priorità fra le alternative esaminate, né per quanto riguarda la scala spazio-temporale di riferimento prescelta.
In particolare l’uso degli indicatori si è rivelato particolarmente utile allo studio delle tematiche agro-ambientali (indicatori agro-ambientali), in relazione alle capacità di rappresentare una notevole quantità di dati, di descrivere il comportamento di fenomeni complessi e di facilitare il trasferimento delle informazioni alle persone o agli organismi che presiedono alle decision
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