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Santa Cruz Cabrália, Brazil

Ludwig F.,UERGS | Fernandes D.M.,Sao Paulo State University | Guerrero A.C.,Sao Paulo State University | Villas Boas R.L.,Sao Paulo State University
Horticultura Brasileira | Year: 2014

The production systems on substrates have been employed in most commercial cultivation of flowers and ornamental plants, including gerbera. However, its introduction as potted flower is recent in Brazil and many studies, especially those related to the determination of substrates physical and chemical properties, which contribute to production quality are still needed. The present study aimed to assess the influence of substrates characteristics for nutrient absorption and production of potted gerbera. The experiment was carried out in greenhouse with the experimental design in randomized blocks, factorial arrangement 5×2 (5 substrates and 2 cultivars) and 4 replications. Treatments consisted of substrates with different physical and chemical characteristics and gerbera cultivars (Cherry and Red). Plants grown on substrate with pH above 7.0 had a reduction in iron absorption, resulting in lower intensity of green coloration in the leaves. Plants grown on substrate with pH below 5.0 showed toxic levels of manganese and lower dry mass. The characteristics of the substrate, especially the pH, influence the nutrients absorption and the production of potted gerbera, altering the final plant quality. Source

Ludwig F.,UERGS | Guerrero A.C.,Sao Paulo State University | Goncalves S.O.,Sao Paulo State University | Fernandes D.M.,Sao Paulo State University | Villas Boas R.L.,Sao Paulo State University
IRRIGA | Year: 2013

Fertigation management of gerbera crop has been many times performed inadequately, and it has been worsened when mixtures of substrates with different physical and chemical characteristics are used. Aiming at evaluating the production and quality of potted gerbera in two substrates and different levels of fertigation, the experiment was conducted in the greenhouse of the DRN/Soil Science, FCA/UNESP, Botucatu (SP). A 5 × 2 factorial randomized block design (5 levels of fertigation and 2 substrates) was adopted with 4 replications. Levels of fertigation corresponded to maintenance of 100% available water (AW) in the substrate; 100 to 80% of AW; 100 to 60% of AW; 100 to 40% of AW and 100 to 20% of AW. The substrates were as follows: 1- mixed coconut fiber (50% pellet coconut fiber and 50% coir fiber), 2- 40% red soil, 40% decomposed pine bark, 10% composition 1 (40% decomposed pine bark, 30% vermiculite and 30% carbonized rice husk) and 10% composition 2 (75% decomposed pine bark and 25% needles of pine). Plants at the marketing stage were evaluated according to the number of leaves; diameter of leaf surface; leaf area; fresh and dry phytomass of leaves, inflorescence and total plant; inflorescence number and diameter, stem diameter, plant height, leaf area rate and electrical conductivity of the substrate solution. Plants of better quality were obtained when they were maintained in levels of 100% available water and the mixed coconut fiber was used as substrate. Source

The study aimed to evaluate the incidence of biological and physiological disorders in the field and postharvested apples cvs. Gala, Fuji and Catarina grown in four production systems: conventional, organic transition, integrated and organic. Apples were evaluated for damages related to biological and physiological disorders in the orchard and after harvest. The greatest damages were attributed to pests, especially Anastrepha fraterculus in the organic system and Grapholita molesta in the organic transition. Apples produced in organic orchards had higher damage levels caused by postharvest physiological disorders than those grown in other production systems. For apples becoming from organic orchards most of the damage was due to lenticels breakdown and degeneration ('Gala'), and bitter pit ('Fuji' and 'Catarina'). The incidence of postharvest rot was not influenced by apple production system. Source

Mota P.R.D.,DEAS CCA UFPI | Villas Boas R.L.,Sao Paulo State University | Ludwig F.,UERGS | Fernandes D.M.,Sao Paulo State University | Folegatti M.V.,University of Sao Paulo
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2014

Rapid tests to assess the nutritional status of plants gerbera can make easier the decision of any adjustments in the fertilization of the substrate. The study was conducted to evaluate nutritionally fertigated gerbera plants with increasing levels of electrical conductivity (EC), using portable meters nitrate and potassium, and chlorophyll. For this, two experiments were conducted. A randomized block design with five levels of EC (0.5, 2.0, 3.5, 5.0 and 6.5 dS m-1) and four replications was used. Cherry cultivar was used in the first experiment. In the second experiment, two cultivars (Cherry and Salmon Rose) were used. In the first experiment, the sap of the leaves was subjected to rapid testing of N-NO3 - (equipment Cardy Horiba C -141). N-NO3 - and K+ (C-131) were determined in the substrate solution. The intensity of the green leaf, in the second experiment was evaluated with portable Chlorophyll Meter. The N content in the indicator leaf in the first and N and K contents in the plant in the second experiment were determined. Rapid tests are presented as good indicators of the level of N-NO3 - and K+ in plant tissue, with the advantages of convenience and speed of determination, facilitating monitoring of fertilization of the substrate by producers and technicians. Source

Bazanella A.S.,Federal University of Rio Grande do Sul | Parraga A.,UERGS
Journal of Control, Automation and Electrical Systems | Year: 2016

Analysis of limit cycles in relay feedback systems is usually performed in continuous time, even though most such systems are implemented digitally. In this paper, we discuss the limitations of the continuous-time analysis, showing that even for standard plants with reasonable sampling rates its results can be considerably far from the truth. Then, we present a discrete-time analysis of relay feedback systems, providing analytical tools that overcome the limitations of their continuous-time counterparts. © 2016, Brazilian Society for Automatics--SBA. Source

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