1,720,962 research outputs found
The simulation of soil water balance: comparison of CropSyst and MACRO model performances.
No full textComparison of WOFOST, CropSyst and WARM for simulating rice growth (Japonica type – short cycle varieties)
No full textThe CropSyst model to simulate the N balance of rice for alternative management
No full textCropSyst is a mechanistic model developed for simulating the growth and development of potentially all herbaceous crops under potential and water/nitrogen (N)-limited conditions. Although the model has been widely used for many crops under different pedo-climatic and management conditions, studies on the simulation of water and N balance for flooded rice are lacking. We evaluated the CropSyst model for simulating the N balance of north-Italian rice fields for scatter-seeded rice grown under continuously flooded conditions. In order to calibrate and validate the model for the processes involved with soil N transformation, data collected in field experiments carried out in northern Italy between 2002 and 2004 were used. The results show the robustness of the model in reproducing the course of the measured soil mineral nitrogen content: the Modeling Efficiencies which describe the agreement between measured and simulated trends, are in most cases positive and the model error fell almost always within the experimental error on the measurements (P = 0.95). Moreover, the model showed the same level of reliability while simulating the nitrogen balances under different levels of nitrogen fertilization, thus depicting it as suitable for comparing N fertilization scenarios. This first attempt at using a model for simulating the nitrogen balance under flooded conditions encourages further studies because of the need of effective tools for optimizing the nitrogen management of flooded rice systems, considered significant sources of groundwater pollution and greenhouse gases in many European rice districts
Nitrate leaching of a continuous maize cropping system for silage production under minimum tillage management
No full textAnalysis of rice sample size variability due to development stage, nitrogen fertilization, sowing technique and variety using visual jacknife
No full textThe determination of sample size before collecting experimental data is fundamental to obtain reliable estimates of variables describing
agroecosystem development. In order to analyze the influence of experimental factors (artificially-induced variability) on rice sample size, an
experiment was carried out in 2004 in northern Italy. In particular, different sample size determinations were carried out for different
fertilization levels, varieties (Indica and Japonica type), development stages, sowing techniques and typologies of the sampling unit. The
obtained sample sizes were compared to investigate the influence of each factor, keeping the others constant (for example, we have compared
the sample sizes computed for different fertilization levels within the same variety, the same phenological stage and the same sampling unit).
Since original data were often not normally distributed and the variances of the original samples were not homogeneous, a new approach for
sample size determination based on a visual evolution of the jackknife was preferred to classical techniques.
Results (expressed as number of plants) showed that (i) sample sizes computed in an early phenological stage (between 21 and 27) are
higher than those calculated for later stages (15–21); (ii) fertilization hides soil N content variability with the consequence that larger sample
sizes are required for unfertilized plots (21–27) compared to fertilized plots (15–27) and (iii) for the early sampling, the Indica type variety
required larger sample size (always 27) with respect to the Japonica type variety (21–24). For row-seeded rice, the number of plants instead of
linear centimeters as the sampling unit led to lower sample sizes (18–27 versus 30–33). These results highlight the influence of experimental
factors and development stage on within-plot variability, and therefore the importance of preliminary samplings for sample size
determinatio
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
Valutazione del modello Armosa per la stima della dinamica di azoto in sistemi cerealicoli della pianura padana
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