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- The effects of the use of organic solid wastes on the growth of citrus treesPublication . Costa, M.; Beltrão, José; De Brito, J. C.; Neves, Alcinda; Correia, Maribela Pestana; Guerrero, CarlosTwo types of organic solid wastes were selected to be applied in a citrus orchard: the sewage sludge (the most common on the settlements) and the manure (the most common on the agricultural fields). The sewage sludge is a residue originated from the wastewater treatment - the solid phase. Its application as an organic fertilizer may represent an alternative to the pollution effects in nature. In an orchard of orange-trees (Citrus sinensis [L.] Osbeck), the application of sludge was compared with the application of manure and with the control in order to observe the growth response of the trees. Biometric methods where used - number of leaves per tree, diameter of the trunk, leaf area, specific leaf areas and leaf chlorophyll content. In general, the citrus plants response to the application of sewage sludge and manure was positive for the plant growth, compared to the control. The application of the manure, and especially the sewage sludge (once this fertilizer / soil amendment is available in larger amounts) may be a profitable alternative application to the use of mineral fertilizers and to other soil amendments. Moreover, as the possible destinations of sewage sludge (sea, deposition in land fields, incineration) provoke environmental problems, its agricultural reuse is essential to avoid those problems, when correctly applied in relation to trace elements and to pathogenic parameters. The reuse of this solid waste may be a clean and a safe technique to preserve the environment contamination.
- Organic compost effects on Stevia rebaudiana weed control and on soil properties in the Mediterranean regionPublication . Coelho, Luísa; Osório, Júlio; Beltrão, José; Reis, MárioStevia rebaudiana Bertoni is a promising crop for semiarid climates, including Algarve region. The objectives of this work were: to compare the feasibility of the eco-friendly stevia weed control strategy with a compost of vegetable residues (grass clippings and pruning’s); to identify the emerged weed species, and to evaluate the effect of compost application on soil properties. Treatments consisted on the application of a 5 cm layer of compost on soil surface or incorporated, and no compost application as control. The trial was set up in six randomized field plots, with four replications. Each plot was divided into three subplots, with one treatment per subplot, in a total of 24 subplots per treatment. Compost application had a distinct effect on weed species. Some species were significantly reduced when compost was applied, namely as mulch. Compost increased soil water content, mainly in area of the trial with lower soil drainage, especially when compost was applied as mulch, as well as other physical and chemical soil properties. Results showed the positive effect of compost on weed control and soil properties during stevia cultivation.
- Effect of irrigation water regimes on yield of Tetragonia tetragonioidesPublication . Bekmirzaev, Gulom; Beltrão, José; Ouddane, BaghdadThe main purpose of this experiment was to study the effect of several irrigation water regimes on Tetragonia tetragonioides (Pall) O. Kuntze in semi-arid regions. During the experiment period, it was measured that several irrigation regimes were affected in terms of growth, biomass production, total yield, mineral composition, and photosynthetic pigments. The experiment was conducted in the greenhouse at the University of Algarve (Portugal). The study lasted from February to April in 2010. Three irrigation treatments were based on replenishing the 0.25-m-deep pots to field capacity when the soil water level was dropped to 70% (T1, wet treatment), 50% (T2, medium treatment), and 30% (T3, dry treatment) of the available water capacity. The obtained results showed that the leaf mineral compositions of chloride and sodium, the main responsible ions for soil salinization and alkalization in arid and semi-arid regions, enhanced with the decrease in soil water content. However, the minimum amounts of chlorophyll, carotenoids, and soluble carbohydrates in the leaf content were obtained in the medium and driest treatments. On the other hand, growth differences among the several irrigation regimes were very low, and the crop yield increased in the dry treatment compared to the medium treatment; thus, the high capacity of salt-removing species suggested an advantage of its cultivation under dry conditions.