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Valle L.A.R.,Federal University of Lavras | Ramos S.J.,Vale Institute of Technology | Pereira H.S.,Federal University of Uberlandia | Amaral D.C.,Federal University of Lavras | And 2 more authors.
Journal of Cleaner Production | Year: 2015

Phosphate fertilizers are critical for crop production in tropical soils, which are known for having high phosphate-fixing capacity and aluminum saturation, as well as low pH and calcium contents. Fluorine is a component of many phosphate rocks used to make phosphate fertilizers, via a process that generates hexafluorosilicic acid (H2SiF6). While many treatment technologies have been proposed for removal of fluorine in industrial facilities, little attention has been given to a process of neutralizing H2SiF6 with calcium oxide aiming to find out an alternative and sustainable use of a by-product with a great potential for beneficial use in tropical agriculture. This study evaluated the effect of a by-product of phosphoric acid production (fluorite with silicon oxide, hereafter called AgroSiCa) on soil properties as well as on growth of soybean and corn. Two experiments (2 crops) were conducted under greenhouse conditions in a completely randomized 3×5×2×3 factorial design as follows: three soils (Red Latosol, Red-Yellow Latosol, and Cambisol), five doses of AgroSiCa (0; 0.5; 1.0; 2.0; 4.0tha-1), two doses of phosphorus (2×%clay and 4×%clay), with three replicates, totaling 90 plots for each experiment. The application of AgroSiCa resulted in a slight increase of soil pH. Significant increases in calcium, phosphate, and silicon levels in soil solution and in shoots of maize and soybean were observed at all doses of AgroSiCa. We also found very low levels of fluoride in all soil leachates. Significant reduction of labile aluminum was found in all soils after the cultivation of maize and soybean. In sum, AgroSiCa improved soil properties and contributed to a better growth of both crops. Our results show that reacting H2SiF6 derived from the wet-process phosphoric acid production with calcium oxide leads to a by-product with potential for agricultural use, especially when applied in highly-weathered soils. Besides providing calcium and silicon to plants, the use of such by-product in soils with high phosphate-fixing capacity and high aluminum saturation delivers additional benefits, since fluoride and silicon can play an important role in improving soil conditions due to the formation of less plant-toxic forms of aluminum, as well as upon decreasing phosphate fixation, thus improving root development and making fertilizer-derived phosphate more available for plant growth. © 2015 Elsevier Ltd. Source


Menezes C.,Brazilian Agricultural Research Corporation | Menezes C.,University of Sao Paulo | Vollet-Neto A.,University of Sao Paulo | Marsaioli A.J.,University of Campinas | And 5 more authors.
Current Biology | Year: 2015

The nests of social insects provide suitable microenvironments for many microorganisms as they offer stable environmental conditions and a rich source of food [1-4]. Microorganisms in turn may provide several benefits to their hosts, such as nutrients and protection against pathogens [1, 4-6]. Several examples of symbiosis between social insects and microorganisms have been found in ants and termites. These symbioses have driven the evolution of complex behaviors and nest structures associated with the culturing of the symbiotic microorganisms [5, 7, 8]. However, while much is known about these relationships in many species of ants and termites, symbiotic relationships between microorganisms and social bees have been poorly explored [3, 4, 9, 10]. Here, we report the first case of an obligatory relationship between the Brazilian stingless bee Scaptotrigona depilis and a fungus of the genus Monascus (Ascomycotina). Fungal mycelia growing on the provisioned food inside the brood cell are eaten by the larva. Larvae reared in vitro on sterilized larval food supplemented with fungal mycelia had a much higher survival rate (76%) compared to larvae reared under identical conditions but without fungal mycelia (8% survival). The fungus was found to originate from the material from which the brood cells are made. Since the bees recycle and transport this material between nests, fungus would be transferred to newly built cells and also to newly founded nests. This is the first report of a fungus cultivation mutualism in a social bee. © 2015 Elsevier Ltd. All rights reserved. Source


Faical B.S.,University of Sao Paulo | Costa F.G.,University of Sao Paulo | Pessin G.,Vale Institute of Technology | Ueyama J.,University of Sao Paulo | And 7 more authors.
Journal of Systems Architecture | Year: 2014

The application of pesticides and fertilizers in agricultural areas is of crucial importance for crop yields. The use of aircrafts is becoming increasingly common in carrying out this task mainly because of their speed and effectiveness in the spraying operation. However, some factors may reduce the yield, or even cause damage (e.g., crop areas not covered in the spraying process, overlapping spraying of crop areas, applying pesticides on the outer edge of the crop). Weather conditions, such as the intensity and direction of the wind while spraying, add further complexity to the problem of maintaining control. In this paper, we describe an architecture to address the problem of self-adjustment of the UAV routes when spraying chemicals in a crop field. We propose and evaluate an algorithm to adjust the UAV route to changes in wind intensity and direction. The algorithm to adapt the path runs in the UAV and its input is the feedback obtained from the wireless sensor network (WSN) deployed in the crop field. Moreover, we evaluate the impact of the number of communication messages between the UAV and the WSN. The results show that the use of the feedback information from the sensors to make adjustments to the routes could significantly reduce the waste of pesticides and fertilizers. © 2014 Elsevier B.V. All rights reserved. Source


Nancucheo I.,Bangor University | Nancucheo I.,Arturo Prat University | Nancucheo I.,Vale Institute of Technology | Grail B.M.,Bangor University | And 3 more authors.
Applied Microbiology and Biotechnology | Year: 2014

An oxidized lateritic ore which contained 0.8 % (by weight) copper was bioleached in pH- and temperature-controlled stirred reactors under acidic reducing conditions using pure and mixed cultures of the acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans. Sulfur was provided as the electron donor for the bacteria, and ferric iron present in goethite (the major ferric iron mineral present in the ore) acted as electron acceptor. Significantly more copper was leached by bacterially catalysed reductive dissolution of the laterite than in aerobic cultures or in sterile anoxic reactors, with up to 78 % of the copper present in the ore being extracted. This included copper that was leached from acid-labile minerals (chiefly copper silicates) and that which was associated with ferric iron minerals in the lateritic ore. In the anaerobic bioreactors, soluble iron in the leach liquors was present as iron (II) and copper as copper (I), but both metals were rapidly oxidized (to iron (III) and copper (II)) when the reactors were aerated. The number of bacteria added to the reactors had a critical role in dictating the rate and yield of copper solubilised from the ore. This work has provided further evidence that reductive bioprocessing, a recently described approach for extracting base metals from oxidized deposits, has the potential to greatly extend the range of metal ores that can be biomined. © 2014 Springer-Verlag. Source


Sahoo P.K.,Indian Institute of Technology Kharagpur | Sahoo P.K.,Vale Institute of Technology | Tripathy S.,Indian Institute of Technology Kharagpur | Tripathy S.,Indian Institute of Technology Bhubaneswar | And 2 more authors.
Journal of Geochemical Exploration | Year: 2014

An integrated study on coal and mine wastes from the Jaintia Hills coalfield of Meghalaya, India involving mineralogy, acid base accounting (ABA), and net acid generation (NAG) potential and sequential leaching was undertaken to examine their potential in controlling the acid mine drainage (AMD). Mineralogical study revealed that pyrite is the major sulfide mineral in coal and mine waste, being more abundant in sandstone and carbonaceous shale; while, dolomite and calcite are abundant in a few shale and siltstones, and Fe and Al copiapites are enriched in sulfate salts. During the ABA test, all coals and > 50% of mine waste showed paste pH < 4, implying their acid generating nature. Further, the relations between net neutralization potential (NNP) and acid producing ratio (APR) revealed that blocky pyrite, pyritiferrous sandstone and efflorescent salts contribute acid much higher than coal, siltstone and carbonaceous shale. This inference is consistent with the NAG test. Partitioning of metals in mine waste indicates high proportions of them in the blocky pyrite being bioavailable than from other rocks. While Mn is highly bioavailable, major portions of Pb and Zn are in the reducible and oxidizable fractions. In efflorescent sulfate salts, >. 80% of metals are available in water soluble fraction; thus these minerals can be considered as the highest polluting residue in the mining environment. These minerals easily precipitate from AMD solution in dry periods and can re-dissolve under rain events because of their high solubility; therefore, they can play an important role in controlling the chemistry of mine drainage in regard to local climate change. In the case of coal, only small fractions of Mn, Ni, Zn, Cd, and Pb are released to the environment, though high proportions of them can become bioavailable under oxidizing conditions besides their other bioavailable forms. © 2014 Elsevier B.V. Source

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