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Browsing by Author "Jesus, J."

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  • Analysis of spatial interpolation for optimising management of a salinized field cultivated with lettuce
    Publication . Panagopoulos, Thomas; Jesus, J.; Antunes, Maria Dulce; Beltrão, José
    The lack of randomisation in irrigation experiments is usually a disadvantage. The introduction of spatial variable experimental design offers a convenient tool to help solving this problem. In order to understand the variation of some soil physical and chemical properties in an experimental block and its effect on lettuce (Lactuca sauna L.) production, graphical interpretation of those soil properties was done with the use of geostatistics in a geographic information system (GIS). In this work three techniques of geostatistics were used for the creation of several maps of soil properties in an experimental plot cultivated with lettuce. Lettuces were evaluated for individual weight and diameter at the end of the cropping season. The soil properties studied were: total mineral nitrogen, phosphorus, potassium, pH, electric conductivity and saturated soil hydraulic conductivity. The techniques used were: ordinary kriging, inverse distance and Thiessen polygon. Cross validation used to compare the prediction performances of the three geostatistical interpolation algorithms determined that kriging was the best technique for each soil property. Prior to the creation of the maps, semivariograms were produced for each soil property. The maps resulting from the interpolation techniques were introduced in a GIS and their values reclassified. After that, spatial modelling was used to develop a final overlay map from all the information of the analysed soil properties simulating a "lettuce production capability map". This final map was created with the objective to determine which areas in the plot had optimal conditions for lettuce development. It was concluded that the plot did not had an optimal area for lettuce production. Localized problems with soil properties were found that could be solved with simple geographically restricted amendment treatments. Final lettuce yield had high correlation (r(2) = 0.83) with the lettuce capability map derived. (c) 2005 Elsevier B.V. All rights reserved.
    2006Journal article Restricted access Show more
  • Using supply chain information for kiwi (Actinidia deliciosa) cv. 'Hayward' fruit quality and production optimization
    Publication . Panagopoulos, Thomas; Jesus, J.; Antunes, Maria Dulce
    The market is increasingly exigent about information on product origin, production inputs, environment impacts and quality. Frequently, information required by postharvest and marketing components must be sourced from the producer. In addition, the information sought from the producer needs to be based on complex data collected under a wide range of field conditions. The objective of this work was to use tools such as, geographic information systems and geostatistics to generate information that could be used to optimise physical and financial aspects of kiwifiruit production systems. Kiwifruits from georeterenced groups of trees were analysed at harvest for yield, soluble solids content (degrees Brix), firmness, and dry matter. From these data were elaborated quality maps for the studied orchard. Those maps can help the producer to make decisions about harvesting time or localized correction of production factors.
    2006Conference object Restricted access Show more