1,720,971 research outputs found
Effect of nitrogen fertilization on sorghum for biomass production
No full textTwo field experiments were carried out in 2005 and 2006 in central Italy in order to
evaluate the effects of different nitrogen (N) application rates (0, 50 100 and 150 kg ha-1) on
flowering date, plant height, biomass production and partitioning (leaves, panicles and stems) and
biomass quality of a sorghum hybrid (H133). Sorghum showed a high potential in terms of
biomass production without N fertilization (18.5 t ha-1 of d.m. in 2005 and 26.6 t ha-1 of d.m. in
2006). The rate that maximized the biomass production was 100 kg ha-1 of N, increasing the
biomass dry weight by 23.8% in 2005 and 18.8% in 2006, with respect to unfertilized sorghum;
higher N rates are not advisable in order to avoid increasing fertilization costs and environmental
impact without benefit of greater biomass production. The two highest N rates when combined
with low water availability appeared to increase the rate of plant development, causing earlier
flowering and increasing the percentage of panicles in total biomass. Higher heating value
(HHV), lower heating value (LHV) and ash concentration of biomass varied among N rates, with
values of HHV and LHV lower for unfertilized sorghum (17.6 and 16.7 MJ kg-1 d.m.,
respectively) than when N was applied (from 19.0 to 19.7 and from 18.1 to 18.8 MJ kg-1 d.m.,
respectively); on the contrary, ash concentration was greater for unfertilized sorghum (7.5% d.m.)
than for fertilized sorghum (from 5.8 to 6.7% d.m.). This research showed the high potential of
sorghum in terms of biomass production also when cultivated with limited irrigation and
fertilization inputs. The biomass dry yield obtained by one hectare of sorghum crop without N
nitrogen fertilization (i.e. 22.6 t ha-1 of d.m., average of 2005 and 2006 values) produces the same
energy, by thermal utilisation, of 9.3 toe, that is equivalent to energy produced by 10,385 L of
diesel fuel or 11,097 m3 of methane fuel. This aspect increases the certainty of the energetic and
environmental sustainability of sorghum crop
Evaluation of chemical weed control strategies in biomass sorghum
No full textTwo field experimental trials were carried out in central Italy, in 2005 and 2006, on biomass
sorghum [Sorghum bicolor (L.) Moench] in order to assess weed control efficacy and selectivity
to the crop of some pre- and post-emergence herbicides applied at different doses
and in different mixtures. All herbicides showed good selectivity to the crop, although postemergence
treatments showed higher transitory phytotoxicity effects than pre-emergence
treatments, especially when high temperatures occurred after treatments, decreasing the
selectivity of leaf herbicides (i.e. MCPA, 2,4-D, bromoxynil and dicamba). Considering
pre-emergence applications, terbuthylazine alone against broadleaves or in mixtures at low
doses with s-metolachlor against mixed infestations (grasses + broadleaves), seemed to be
the best options to obtain a good selectivity to the sorghum and a high weed control level.
Aclonifen showed some limits in terms of weed spectrum and could be recommended
only against simplified broadleaf weed infestations without the presence of less susceptible
weeds, like Amaranthus retroflexus, Portulaca oleracea and Solanum nigrum. Propachlor
seemed not to be advisable due to the low efficacy against all the major broadleaf warmseason
weed species in the Mediterranean areas. Considering post-emergence applications,
all treatments gave quite similar results in terms of weed control, although, the mixture of
terbuthylazine + bromoxynil seemed to be the best option due to bromoxinil’s higher efficacy
than other foliar herbicides, such as MCPA, 2,4-D and dicamba, which can increase
the efficacy of terbuthylazine alone especially under dry weather conditions. There were
no significant differences in sorghum biomass between herbicide treatments, although,
the more selective pre-emergence treatments showed, on average, a higher biomass yield
value than the less selective post-emergence treatments. For these reasons, biomass values
seemed to be more related to herbicide selectivity than to herbicide efficacy, especially in
cases of scarce competitiveness of weed flora
Mechanical weed control in onion seed production
No full textTwo field experiments with onion (Allium cepa L.) cultivated by the “seed-to-seed” and “bulb-to-seed” methods for the organic seed production were carried out in central Italy in order to evaluate the effects of some mechanical methods (harrowing, hoeing, hoeing-ridging, split-hoeing, finger-weeding, manual weeding) on: i) weed control; ii) selectivity to the onion; iii) onion seed production. The results showed that the choice of the seed production method and then the mechanical treatments require to be managed very carefully in order to maximize the weed control, reducing seed yield losses. The seed-to-seed method seemed to be not advisable in the Mediterranean areas, because there were great difficulties to control weeds by mechanical method mainly owing to the long crop cycle with more fluxes of weed emergence, the very low competitiveness of onion at the early growth stages and the weather conditions during the crop cycle that has greatly affected the timeliness, repeatability and effectiveness of mechanical control. In these conditions, competition of uncontrolled weeds caused heavy seed yield losses or the crop failure and only manual weeding ensured a satisfactory weed control and seed yield, although with a very high hand labour. The bulb-to-seed method was the only advisable for onion seed production because allowed to control weeds by mechanical methods, obtaining good levels of seed yield. In particular, combined intra and inter-row methods, such as hoeing-ridging or split-hoeing + finger-weeding, allowed a high effectiveness against weeds (ranged from 63% to 92%) and a good selectivity to the crop, reducing weed-crop competition and assuring satisfactory onion seed production. Unlike seed yield, seed quality was not affected by weed competition: weight, moisture and germinability of onion seeds were always over of the standard levels required for commercialization, regardless of weed competition levels
Dose–Response Curves of Pelargonic Acid against Summer and Winter Weeds in Central Italy
No full textPelargonic acid is a non-selective post-emergence contact bio-herbicide which is registered both for cropping and non-cropping uses in several countries. Dose–response curves on the efficacy of pelargonic acid against common weeds in Mediterranean areas are not available. Dose–response curves of pelargonic acid efficacy against summer and winter annual weeds were evaluated in two field experiments (winter exp. in 2019 and summer exp. in 2020) in central Italy. Pelargonic acid was applied at five doses (1.4, 2.7, 5.4, 10.9 and 21.8 kg a.i. ha−1). Data on weed density, weed dry weight, and weed ground cover were used to calculate the efficacy of pelargonic acid against winter and summer weeds. Data were subjected to a non-linear regression analysis using the logistic dose–response model. Dose of pelargonic acid required to obtain 50%, 70%, 90% and 95% weed control against each weed species (ED50, ED70, ED90 and ED95) were estimated. ED values allowed us to classify winter and summer weeds with respect to their susceptibility to pelargonic acid (ED50 values in kg ha−1 are reported in parenthesis): Kickxia spuria (2.6) (more susceptible) > Heliotropium europaeum (3.0) > Echinochloa crus-galli (3.4) > Solanum nigrum (3.6) > Stachys annua (5.3) > Papaver rhoeas (6.5) > Veronica hederifolia (10.3) > Amaranthus retroflexus (11.4) > Matricaria chamomilla (11.6) > Portulaca oleracea (18.7) > Lolium multiflorum (>21.8) (less susceptible). These findings will allow for the optimization of weed control by pelargonic acid and its use in weed management strategies, both in organic and sustainable cropping systems, under different environmental conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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