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Tecniche agronomiche innovative per la produzione di semente certificata di riso (Oryza sativa L.)in regime biologico
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CROP COEFFICIENT (Kc) DETERMINATION IN SPRINKLER IRRIGATED RICE
No full textExperimental trials were carried out in Sardinia in 2002 and 2003, in order to obtain first information on kc values at different phenological stages in sprinkler irrigated rice; in 2003 the trials differed for the sowing date.
An equipment recording soil moisture content every 10 cm up to 100 cm depth was used to obtain the water balance for the first soil layers. Result analysis highlighted that the layer up to 20 cm covers about 80 % of the crop water requirements for the whole cycle.
The results show a variability particularly related to the meteorological trend during the trials. Crop coefficient ranged between 0.2 and 0.75 (estimated value) for the initial stage (Kcini), between 0.85 and 1.0 for mid season stage (Kcmid) and was 0.2 for late season (Kcend)
Roots system development in flooded and sprinkler irrigated rice cultivars
No full textOne of the most important factors to obtain high yield is a good root system development.
The exploration of a greater soil mass allows a higher water and nutrient uptake and increases crop yield. Numerous authors noticed a significant correlation between yield and root system dimension.
The growing environment, and therefore the agronomic technique, affect root system
development.
Traditionally rice is grown by flooded irrigation that, due to oxygen lack in deep soil layers, brings to a low root system deepening. In upland rice, where the growing does not take place with continuous flooding, some authors noticed a good root system development.
A comparison trial, with national and selected for upland conditions rice cultivars, was carried
out to evaluate root system development adopting both traditional flooded irrigation and sprinkler irrigation. Root density was determined by Newman method for different soil depths.
Results highlight a greater root density in flooded crop in comparison to sprinkler irrigation.
The higher yield obtained with sprinkler irrigation, even higher than flooding irrigation, suggest a greater efficiency of the root system in water and nutrient uptake in oxidized environment
Water use and crop coefficients in sprinkler irrigated rice
No full textAbstract
Field experiments were carried out during the years 2002, 2004, 2005 and 2006 to analyze water-soil-atmosphere in- teractions in sprinkler irrigated rice. The research was carried out in Sardinia (39o59’ N; 8o40’ E, at altitude 15 m). The cultivars used in the experiments, respectively in 2002 and in 2004-2005-2006, were Irat 212 and Eurosis. In each year cultivars were subjected to the same crop management. Irrigation was applied since the emergence with the sprinkler method, taking into account the loss of water from ‘Class A’ pan evaporation. Soil water content was monitored at 0.10 m intervals until 1.00-m depth using a ‘Diviner 2000’ (Sentek). In 2002 seven irrigation schedul- ing treatments were compared. In 2004, 2005, 2006 irrigation treatments provided for optimal soil water conditions during the growing season.
In 2002 the results highlighted: 1) 0-0.20 m depth was the most important layer for crop water uptake and the best correlated layer with rice rough yield; 2) the positive relationship between yield and water supply was significant until 6500 m3 ha-1 of water applied. Further seasonal irrigation volumes did not increase significantly yield. In 2004, 2005 and 2006 the analysis of the soil water balance at different crop phenological stages allowed to esti- mate crop coefficients (Kc) using the Penman-Monteith equation and the ‘Class A’ pan evaporation (Kcev).
Kc varied over the three-year period on average from 0.90 to 1.07 and 0.97, respectively for the emergence-end of tillering, end of tillering-heading and heading-maturing periods, while crop coefficients as a ratio between maximum crop evapotranspiration (ETc) and Epan, Kcev ranged from 0.78 to 0.92 and 0.81 for the same time periods
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
AN ALTERNATIVE TO THE FLOODED IRRIGATION OF RICE: PRELIMINARY TESULTS ON WATER REQUIREMENT IN DRYLAND ENVIRONMENTS
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