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According to some studies, the use of forest biomass for the generation of electric power and/or heat would result in a significant reduction in the emission of greenhouse gases. This would happen even in the case of soils substitution that currently have an agricultural use although its implementation would require more studies on the environmental impact that they could have in each particular case. In this study, the potential of electric power production is evaluated with several species of Eucalyptus planted in short rotation forestry systems. Three species were evaluated: E. benthamii, E. dunnii and E. grandis in four spacings: 3 × 1.5 m, 3 × 1 m, 3 × 0.75 m, 3 × 0.5 m, in two sites in the northern and western areas of Uruguay during a period of 76 and 75 months, respectively. During this period, the following parameters were evaluated: higher heating value, wood density, energy density and energy yield per hectare and per year. The results obtained show that the heating value changes slightly with the planting density and age. The average of higher heating values were 19,787 versus 19,454 J g−1 and 19,867 versus 9909 J g−1for the planting densities of 2220 versus 6660 trees ha−1 at Paysandu and Tacuarembo, respectively, at 76 months. Higher heating value increased from 19,665 to 19,745 J g−1 at 18 months to 19,740 and 19,914 J g−1 at 76 months for Paysandu and Tacuarembo, respectively. The wood density, depending on the site, is affected by age, species and planting density. On average, wood density increased (only at Paysandu) from 0.405 g cm−3 at age 18 months to 0.497 g cm−3 at age 76 months. There is a negative relationship between the heating value and the wood density. The energy yield is basically explained by the production of biomass. At Tacuarembo, a stronger relationship between energy production and planting density is obtained (1012 vs. 636 MW ha−1 for 6660 and 2220 trees ha−1, respectively) compared to the Paysandu site (1093 vs. 912 MW ha−1 for 6660 and 2220 trees ha−1, respectively). Harvest times are different in each site depending on the IMA values obtained.

Soils are a key issue in the management of global environmental changes and food supply. The goal of this work was to characterize the soil changes that were promoted by agriculture in Uruguay in the period 2002–2014. We analysed the association between pH, Ca2+, Mg2+, K+, Na+ and soil organic carbon (SOC) and its tendency through the years of soil analysis database 2002–2014 that belong to Experimental Station Alberto Boerger INIA La Estanzuela (Colonia, Uruguay). During the study period, the average soil pH, SOC, and exchangeable base content across the archive sample set were reduced. The exchangeable K+ content decreased by 0.04 mmol kg−1 year−1 with the increase in grain production. The SOC decreased by 0.43 mg (g year)−1 even when most agricultural activity followed a no-tillage system. A reduction of 0.02 units of pH per year also occurred. If these changes continue in the future, agricultural soils will significantly decrease their food production potential, and will not be adequate for sustainable crop production.

Short-rotation plantations have been suggested to develop renewable energies in South America. Our study evaluated the biomass production of Eucalyptus benthamii, E. dunnii and E. grandis plantations at stocking densities of 2220, 3330, 4440 and 6660 trees ha−1 in the North (Tacuarembo) and West (Paysandu) of Uruguay, over a 76-month period. The species survival was not related to planting density, and the highest mortality rates occurred at Tacuarembo. The effects of tree competition were more evident for E. grandis. At Tacuarembo site, the average survival of the species were: 57, 57 and 46% at age 76 months for E. benthamii, E. dunnii and E. grandis, respectively. Survival rates were similar for the different planting densities, with ranges between 50 and 57%. At Paysandu site, the average survival of the species were: 83, 86 and 75% for E. benthamii, E. dunnii and E. grandis, respectively, with a range from 78 to 84% for different planting densities. Weather conditions (temperature and rainfall) were similar at both sites throughout the evaluation period. Wood density and individual and total biomass weight (kg tree−1 and Mg ha−1, respectively) were evaluated sampling destructively 2592 trees and logarithmic biomass equations were developed using the diameter at breast height (cm) and total height (m) of the trees. Wood density increased with the age of the crop only at Paysandu. On average, wood density increased from 0.405 g cm−3 at age 18 months to 0.497 g cm−3 at age 76 months. The highest wood density was observed at 76 months on E. benthamii (0.413 and 0.431 g cm−3) and E. dunnii (0.496 and 0.539 g cm−3) at Tacuarembo and Paysandu, respectively. Age had no effect on the wood density at Tacuarembo. The stem biomass showed an inversely-proportional relationship with the planting density. Individual stem biomass was higher for E. grandis (81 and 74 kg tree−1 on average at Tacuarembo and Paysandu, respectively) than for the other species. The highest biomass per hectare was achieved for the highest planting density, specifically for E. dunnii (193 Mg ha−1) and E. grandis (203 Mg ha−1) at Paysandu and for E. dunnii (157 Mg ha−1) at Tacuarembo. At both locations, the effects of contrasting planting densities on biomass production increased throughout the rotation.

Eucalyptus grandis and E. dunnii have high productive potential in the South of Brazil, Uruguay, and central Argentina. This is based on the similarity of the climate and soil of these areas, which form an eco-region called Campos. However, previous results show that these species have dierences in their distribution caused by the prioritization of Uruguayan soils for forestry, explained by the particular conditions of each site. In this study, the site variables (climate, soil, and topography) that better explain the distribution of both species were identified, and prediction models of current and future distribution were adjusted for dierent climate change scenarios (years 2050 and 2070). The distribution of E. grandis was associated with soil parameters, whereas for E. dunnii a greater eect of the climatic variables was observed. The ensemble biomod2 model was the most precise with regard to predicting the habitat for both species with respect to the simple models evaluated. For E. dunnii, the average values of the AUC, Kappa, and TSS index were 0.98, 0.88, and 0.77, respectively. For E. grandis, their values were 0.97, 0.86, and 0.80, respectively. In the projections of climatic change, the distribution of E. grandis occurrence remains practically unchanged, even in the scenarios of temperature increase. However, current distribution of E. dunnii shows high susceptibility in a scenario of increased temperature, to the point that most of the area currently planted may be at risk. Our results might be useful to political government and foresters for decision making in terms of future planted areas.© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Experimental scale crops for Eucalyptus grandis, Eucalyptus benthamii, Eucalyptus dunnii and Eucalyptus tereticornis, at 2,220, 4,440 and 6,660 trees ha−1 were established in two soil units, at Paysandú and Tacuarembó, Uruguay. Wood samples were taken from twenty-two-months-old trees, and were used to produce bioethanol by pre-hydrolysis simultaneous saccharyfication and fermentation process (PSSF). Cellulose and lignin content was analyzed. Species and planting density affected biomass production at both sites; the highest value was obtained with E. dunnii at 6,660 trees ha−1 at Paysandú. Cellulose content of wood varied between species at both sites, but only between planting densities at Tacuarembó. The site effect showed that the highest amount of cellulose (14.7 Mg ha−1) was produced at Paysandú. E. benthamii and E. tereticornis wood showed higher lignin contents, conversely, the PSSF yields showed no differences, which led to a bioethanol average of 97 L Mg−1. Bioethanol productivity was associated to the biomass productivity. It was possible to obtain 2,650 L ha−1 of bioethanol using wood from E. benthamii, E. dunnii and E. grandis at 4,440 and 6,660 trees ha−1 at Paysandú, and with E. benthamii at 4,440 and 6,660 trees ha−1, and E. dunnii at 6,660 trees ha−1 at Tacuarembó., Eucalyptus species, High planting density, Short rotation forestry, Biomass, Bioethanol

In recent decades, there has been increasing eutrophication of rivers and lagoons in Uruguay and solutions leading to water purification are being sought. The growing pollution has been attributed to nitrogen and phosphorus compounds exported from the river basins with intensification of agricultural production and the absence of tertiary treatment for urban and industrial effluents. Although nitrogen and phosphorus are relevant to eutrophication, there are also other factors that can promote eutrophication and algal blooms. This paper reports a broad analysis of water quality variables recorded over 9 years (2009–2018) at 17 sampling stations on the Uruguay River and 16 sampling stations on the Rio Negro, and explores their relationship with the changes of chlorophyll a (Chl-a) concentrations using a generalized linear model and a neural network simulation (NNS). The input variables were total phosphorus; total suspended solids; electrical conductivity of water (ECw); alkalinity; water temperature (T); water pH (pH) and sampling month. The NNS explained 79% of Chl-a variations and showed the most relevant variables to be T, ECw, and pH. Moreover, the NNS showed that replacement of current land uses by natural prairie would not significantly reduce Chl-a concentrations. The results showed that the main factors that drive Chl-a concentrations (i.e., algae) are not directly linked to agriculture land use.

The current global climate change, the 2030 Agenda, and the planetary boundaries have driven new development strategies, such as the circular economy, bioeconomy, and biorefineries. In this framework, this study analyzes the potential availability and sustainability of the wood supply chain for a small-scale biorefinery aiming at producing 280–300 L of bioethanol per ton of dry biomass, consuming 30,000 t of dry biomass per year harvested in a 50 km radius. This wood production goal was assessed from Eucalyptus grandis stands planted for solid wood in northeastern Uruguay. Moreover, to understand the environmental performance of this biomass supply chain, the energy return on investment (EROI), carbon footprint (CF), and potential soil erosion were also assessed. The results showed that the potential wood production would supply an average of 81,800 t of dry mass per year, maintaining the soil erosion below the upper threshold recommended, an EROI of 2.3, and annual CF of 1.22 kg CO2−eq m−3 (2.6 g CO2−eq MJ−1). Combined with the environmental performance of the bioethanol biorefinery facility, these results would show acceptable values of sustainability according to EU Directive 2009/28/ec because the bioethanol CF becomes 1.7% of this petrol’s CF.

Bioenergy is the most widely used type of renewable energy. However, an assessment of water consumption and pollution is necessary to determine the water demand of this energy source. The Uruguayan public policy to decarbonize energy sources highlighted the use of bioenergy. In this regard, we analyzed the water footprint (WF) of four bioethanol cropping systems: (1) maize-wheat-sorghum rotation without harvested crop residues (MWS), (2) maize-wheat-sorghum rotation with harvested crop residues (MWS-R), (3) continuous sweet sorghum (Ss), and (4) switchgrass (Sw). In order to assess the WF of bioethanol production, green (WFgreen) and gray (WFgray) components of crop production were calculated by considering the different volumes of water involved in evaporation, rainfall, and fertilizer pollution. Annual cropping systems (i.e., MWS, MWS-R, Ss) had the largest WFs (23.1–30.9 m 3 L e t h a n o l − 1 ). Switchgrass had the lowest values per hectare and per liter of ethanol (12,735 m3(ha yr)−1 and 3.8 m 3 L e t h a n o l − 1 , respectively). The volume required to assimilate phosphorous (P) and nitrogen (N) fertilizers played a significant role in bioethanol cropping systems. In annual systems, WFgray was the main fraction (87%) of total WF (WFT). Averaged across all cropping systems, WFgray related to P was 13 times larger than WFgray related to N.

Over the last decade, Uruguay has expanded and intensified its rainfed crop production. This process has affected beekeeping in several ways: for example, by reducing the space available. This has increased the density of apiaries, the risk of varroosis and acaricide use. Additionally, the dominance of no-tillage crops has increased the frequencies of application and of loads of pesticides in regions where such crops share the land with beekeeping and honey production. Therefore, the exposure of bees to xenobiotics (agricultural pesticides and veterinary products) has increased in line with pollution of hives and their products. To document pollution from hive exposure to pesticides, we surveyed the presence of 30 xenobiotics normally used in Uruguay, in recycled beeswax (RB) and in honey cappings (HC) from the main Uruguayan beekeeping regions. There was contamination of all the analyzed samples (RB and HC) with the herbicide atrazine at a range of 1-2 ng g-1. At least three or four additional xenobiotics were detected: insecticides (chlorpyrifos-ethyl and thiacloprid); fungicides (azoxystrobin and tebuconazole); and veterinary products (coumaphos, ethion, and tau-fluvalinate). The frequency of detection of chlorpyrifos-ethyl and coumaphos in RB samples was higher than in those of HC. Moreover, the concentrations of azoxystrobin, coumaphos, and tebuconazole in RB samples were higher than in HC samples. Therefore, we suggest the use of HC to produce recycled printed beeswax films for use in hives to minimize pollution transfer.

Sustainable rice production systems are key to food security. Diversified farming systems are essential for ecological intensification and environmental enhancement. Energy use efficiency is one of the main sustainability indicators in agroecosystems. Thus, an assessment of consumption and efficiency of energy in contrasting cropping systems can discriminate their management practices and components sustainability. The goal of this study was to evaluate the energy performance through energy return on investment (EROI) in four rice-based rotation systems that belong to a long-term experiment located in the Temperate Grassland Terrestrial Ecoregion, at the Atlantic side of South America. Rotations analyzed consisted in: a) continuous rice ( R c ); b) rice-soybean ( R − S ); c) rice-pasture for 1.5 years ( R − P S ); and, d) rice-pasture for 3.5 years ( R − P L ). The EROI estimations considered all the inputs and outputs of energy from cradle to farm gate. The greatest EROI was observed in R–S (7.2 M J M J − 1 ) and the lowest energy consumption in R − P L (10,607 M J ( h a y r ) − 1 ). The R − P L ’s EROI (6.7 M J M J − 1 ) was 6.5% and 8% higher than R c and R − P S EROI, respectively. Rotations without pastures produced 79% more energy compared with rotations including pastures. However, energy inputs of rice-pasture rotations were 40% lower than either R − S or R c . The EROI (without animal production) of R − P S , R–S and R c was 25%, 28% and 43% lower than the EROI of R − P L (10 M J M J − 1 ), respectively. For the analyzed South American ecoregion, EROI assessments of four business as usual rice production systems allowed to discriminate and hierarchize their sustainability and diversity.

Experimental scale crops for Eucalyptus grandis, Eucalyptus benthamii, Eucalyptus dunnii and Eucalyptus tereticornis, at 2,220, 4,440 and 6,660 trees ha−1 were established in two soil units, at Paysandú and Tacuarembó, Uruguay. Wood samples were taken from twenty-two-months-old trees, and were used to produce bioethanol by pre-hydrolysis simultaneous saccharyfication and fermentation process (PSSF). Cellulose and lignin content was analyzed. Species and planting density affected biomass production at both sites; the highest value was obtained with E. dunnii at 6,660 trees ha−1 at Paysandú. Cellulose content of wood varied between species at both sites, but only between planting densities at Tacuarembó. The site effect showed that the highest amount of cellulose (14.7 Mg ha−1) was produced at Paysandú. E. benthamii and E. tereticornis wood showed higher lignin contents, conversely, the PSSF yields showed no differences, which led to a bioethanol average of 97 L Mg−1. Bioethanol productivity was associated to the biomass productivity. It was possible to obtain 2,650 L ha−1 of bioethanol using wood from E. benthamii, E. dunnii and E. grandis at 4,440 and 6,660 trees ha−1 at Paysandú, and with E. benthamii at 4,440 and 6,660 trees ha−1, and E. dunnii at 6,660 trees ha−1 at Tacuarembó.

The massive use of pesticides and herbicides to increment the agriculture production can produce severe environmental impacts. This implies the need of new methods to monitor and control the use of chemical agents. An alternative to traditional sampling methods is the use of insects to act as a biological distributed sensor in order to monitor the presence of pesticides in the neighbourhood. Specifically, several authors have proposed the use of the beehive as a distributed sensor. To evaluate critical changes in the beehive behaviour, the sound patterns are analysed. In this work the guidelines used to develop a remote monitoring system in order to detect abnormal changes in the sound patterns in hives are presented. The evolution of the frequency spectrum sampled in four temporal windows is proposed to monitor the beehive health. Experiments to determinate the frequency band and the frequency resolution are presented for the case of Apis mellifera . Using these guidelines a complete monitor system was developed and constructed.

Forest biomass is an interesting option for bioenergy generation, however sustainability aspects should be carefully considered. In this context, the nutrient exportation is a key factor for reach a sustainable biomass production by an adequate harvest decision about what tree's fractions will export less nutrients of farms. In this work biomass production per fraction and nutrient export for three eucalypt species (Eucalyptus benthamii, E.dunnii and E.grandis) planted at four planting densities: 2220, 3330, 4440 and 6660 trees per hectare, in two different sites, were evaluated at the age of 76 months. The assessed nutrients were: P, Ca, Mg, K and N in bark, branches, leaves, and stemwood fractions. Nutrients use efficiency and the balance between available cations in the soil (Ca, Mg and K) vs their export in the different tree components were assessed. The effect of the interaction (species x planting density) for almost all the variables evaluated was not significant in both sites. The nutrients concentration is slightly affected by the planting density while the nutrient export is significantly related to this parameter in both sites. Bark is the fraction with the higher Ca and Mg concentration values, whereas the higher concentrations of N and K were found on the leaves, meanwhile debarked stemwood is the fraction with the lower nutrient concentration. In the short term, K would be the nutrient that will exhaust first, although the use of stemwood allows an important reduction in the use of cations. Even with low planting densities it is possible to obtain high biomass yields and similar to those achieved with the lowest spacing in particular at the Paysandu site.

Soil erosion byrainfall is a process that demands management, both for the prevention of excessive soil erosionand for the protection of the quality of freshwater bodies. Erosion coefficients (K-factors) of theuniversal soil loss equation (USLE)/revised USLE (RUSLE) model were assigned to 99 mappedUruguayan soil types at 1:1,000,000 scale. This work developed a linear mixed model (LMM)with 79 soils with assigned K-factors, in which the following variables were considered: soiltaxonomy, chemical composition, and parent material. The developed LMM had an R 2 =0.86,in which the soil taxonomy (p

Soil erosion can be accelerated by agricultural intensification, and the soil loss can alter the quality of water bodies. Sustainable agricultural production therefore requires the management of erosion and potential water pollution. In Uruguay, where there is heavy use of soil for agriculture, there is a need to continually develop and update erosion management policies. In this framework, we estimated the erosion in 99 drainage basins by analyzing and managing the information required (K, L, S, C and R-factors) in the universal soil loss equation (USLE) and the revised universal soil loss equation (RUSLE) in a geographical information system (GIS). The studied drainage basins encompass 73% of the area of Uruguay. The results include the following values: the K-factor range from 0.0073 to 0.088 (t ha h)(ha MJ mm)−1, the R-factor range from 3,547 to 9,342 (MJ mm)(ha h yr)−1, the C-factor range from 0 to 0.155, the slope gradients are less than 4.3% in 78% of the soils, and the multiplicative products of L and S are less than 0.73 in 75% of the cases. The drainage basin characteristics allowed the identification of 4 homogeneous regions based on their erosion behavior. The northern-western-southern basins cluster and Sierras del Este basins clusters indicate the possibility of managing their erosion through control of vegetation cover, which is represented by the C-factor. In general, this forecast of soil erosion by water (92.9% of the soil polygons and 99.9% of the drainage basins) indicates a mean soil loss of less than 7 t (ha yr)−1 corresponding to the land cover surveyed in 2011. Resumen La erosión del suelo puede ser acelerada por la intensificación agrícola, y el sedimento generado puede alterar la calidad de los cuerpos de agua. Por lo tanto, la producción agrícola sostenible en términos de erosión y contaminación potencial del agua requiere una capacidad para manejar la erosión. En Uruguay, donde hay un uso intensivo del suelo por la agricultura, es necesario desarrollar y actualizar continuamente las políticas de manejo de la erosión. En este marco, estimamos la erosión en 99 cuencas de drenaje analizando y manejando la información requerida (K, L, S, C y R) por la ecuación universal de pérdida de suelos (USLE/RUSLE) en un sistema de información geográfica (SIG). Las cuencas estudiadas abarcan el 73% de la superficie del Uruguay. Los resultados incluyen los siguientes valores: los factores K van desde 0.0073 hasta 0.088 (t ha h)(ha MJ mm)−1, los factores R van desde 3,547 a 9,342 (MJ mm)(ha h año)−1, los factores C van desde 0 a 0.155, las pendientes son menores al 4.3% en el 78% de los suelos y los productos de L y S son menores a 0.73 en el 75% de los casos. Las características de las cuencas de drenaje permitieron identificar 4 regiones homogéneas en base a su comportamiento erosivo. Las agrupaciones norte-oestesur y Sierras del Este apuntan a la posibilidad de manejar su erosión a través del control de la cubierta vegetal, representada por el factor C. En general, este pronóstico de erosión hidráulica (92.9% de los polígonos del suelo analizados y 99.9% de las cuencas de drenaje) indica una pérdida media de sedimentos de menos de 7 t (ha año)−1 correspondiente a la cubierta del suelo estudiada en 2011.

Glyphosate-resistant soybean cultivation is expanding rapidly in Uruguay, with its land area having increased by 95 times during the past 10 years. Because of the region's Neotropical conditions, insecticide use is required to ensure adequate soybean productivity. However, in areas shared by soybean crops and beekeepers - such as the southwestern zone of Uruguay (SWZU) - the use of insecticides can increase the risks of honeybee death and honey contamination. Uruguayan commercial and legal guidelines set out practices and field doses designed to prevent acute intoxication with insecticides. However, honeybees in the SWZU are predominantly a polyhybrid subspecies different from that used to set international reference values, and hence they may have a different acute toxicity response, thus rendering such precautions ineffective. The aim of this work was to assess the acute toxicity response of polyhybrid honeybees in the SWZU to cypermethrin (commercial formulation: Cipermetrina 25 Agrin®), chlorpyrifos (commercial formulation: Lorsban 48E®), and endosulfan (commercial formulation: Thionex 35®). Acute toxicity bioassays were conducted to determine the median lethal dose (LD(50)) of each insecticide for the honeybees. The results indicate that, compared with EU reference values, SWZU honeybees have a higher toxicological sensitivity to chlorpyrifos and endosulfan, and a lower toxicological sensitivity to cypermethrin, based on the commercial formulations tested. However, when these results were adjusted according to their field dose equivalents, only chlorpyrifos emerged as a potential problem for beekeeping, as the maximum recommended field dose of Lorsban 48E® for soybean crops in Uruguay is 23 times the corresponding LD(50) for honeybees in the SWZU.

This work studies the acute contact toxicity of oxalic acid (OA) on a honeybee polyhybrid subspecies (Apis mellifera), which is the dominant biotype in southwestern zone of Uruguay (SWZU) and the country's most important honey-producing region. We determined the mean lethal dose (LD50), as well as the no observed effect level (NOEL) and the lowest observed effect level (LOEL) values. We also estimated the total number of honeybees per hive in the test area. The aim was to assess the relationship between the maximum OA dose used in Uruguay (3.1 g OA per hive) and the toxicological parameters of honeybees from SWZU. The current dose of 3.1 g OA per hive corresponds to 132.8 OA per honeybee since determined NOEL is 400 OA per honeybee; our results indicate that the current dose could be increased to 9.3 g OA per hive. The results also highlight some differences between the LD50 value in SWZU honeybees (548.95 OA per honeybee) and some published LD50 values for other honeybee subspecies.Este trabajo estudió la toxicidad aguda por contacto del ácido oxálico (AO) sobre una subespecie poli-híbrida de abejas (Apis mellifera), la cual es el biotipo dominante en la zona sudoeste de Uruguay (SWZU), la región más importante para la producción de miel en este país. Este estudio determinó la dosis letal 50 (DL50), así como el nivel de efecto no observado (NOEL), el nivel de efecto mínimo observado (LOEL), y el número total de individuos por colmena. El propósito fue evaluar la relación entre la dosis máxima de AO usada en Uruguay (3.1 g AO por colmena) y los parámetros toxicológicos de las abejas de la SWZU. Los resultados mostraron que es posible elevar la dosis actual de AO por colmena a 9.3 g, ya que la dosis actual de 3.1 g de AO corresponde a 132.8 AO por abeja, y el NOEL determinado es 400 AO por abeja. Los resultados también destacaron algunas diferencias entre la DL50 de las abejas del SWZU (548.95 AO por abeja) y algunos valores de DL50 publicados para otras subespecies de abejas.

The influence of insecticides commonly used for agricultural purposes on beehive depopulation in Uruguay was investigated. Honeycombs, bees, honey and propolis from depopulated hives were analyzed for pesticide residues, whereas from active beehives only honey and propolis were evaluated. A total of 37 samples were analyzed, representing 14,800 beehives. In depopulated beehives only imidacloprid and fipronil were detected and in active beehives endosulfan, coumaphos, cypermethrin, ethion and chlorpyrifos were found. Coumaphos was present in the highest concentrations, around 1,000 μg/kg, in all the propolis samples from active beehives. Regarding depopulated beehives, the mean levels of imidacloprid found in honeycomb (377 μg/kg, Standard Deviation: 118) and propolis (60 μg/kg, Standard Deviation: 57) are higher than those described to produce bee disorientation and fipronil levels detected in bees (150 and 170 μg/kg) are toxic per se. The other insecticides found can affect the global fitness of the bees causing weakness and a decrease in their overall productivity. These preliminary results suggest that bees exposed to pesticides or its residues can lead them in different ways to the beehive.

This study presents a yield model for aboveground biomass production from three species the Eucalyptus in northern and western regions of Uruguay, based on sampling records from intensive crop plantations. High-density eucalyptus plantations represent a forestry alternative for the production of forest biomass. This work assessed the survival and growth of three eucalyptus species (Eucalyptus benthamii Maiden &amp, Cambage, E. dunnii Maiden and E. grandis Hill ex Maiden) planted at densities of 2220, 3330, 4440 and 6660 trees ha&minus, 1, for a period of 57 months in northern (Tacuaremb&oacute, ) and western (Paysand&uacute, ) regions of Uruguay. Linear and logarithmic equations of individual volume were fitted by site and species. The survival of E. grandis, E. benthamii and E. dunnii was not related to planting density, and the highest mortality values occurred in Tacuaremb&oacute, The effects of competition among trees were more evident at the highest planting density for E. grandis. In all species, the reduction in diameter was more marked than that of height, as planting density increased. Tree volume showed the same trend, and this was higher with higher planting densities. At Tacuaremb&oacute, the volume was the highest with E. benthamii at 6660 trees ha&minus, 1 (416.4 m3 ha&minus, 1), and, at Paysand&uacute, the highest production was obtained with E. grandis (370.7 m3 ha&minus, 1) and with the densities of 4440 and 6660 trees ha&minus, 1 (305.9 and 315.3 m3 ha&minus, 1, respectively). With all species and planting densities, there was an increase in the accumulated volume during the 57-month study period, however, growth curves indicate that the maximum production per unit time and, therefore, the optimum harvest time occurred at 48 months. In this work, it has been shown that the use of intensive short-rotation plantations of eucalyptus for the production of biomass in Uruguay is suitable in soils prioritized for forestry.

Sediment constitutes an important sink of endocrine disruptor compounds; however, the potential of sediments to act as a source of endocrine disruptors should be more extensively investigated. The main objective of this study was to determine whether exposure of immature common carp to Uruguay River sediments undergo physiological and endocrine alterations. The lower Uruguay River watershed supports intensive agricultural and forest production, receives municipal sewage discharge and industrial effluent, and a new large pulp mill was constructed in 2006. A 30-day semi-static assay was performed using sediments from four sites along the Uruguay River and compared with an unexposed group in dechlorinated water as a negative control. We focused on two upstream and two downstream sites of a new elemental chlorine free pulp mill. The results showed that plasma vitellogenin levels increased in fish along the river and significant differences were found between the exposed and unexposed groups. Condition factor and gonadosomatic index were not different; however, a significant difference in hepatosomatic index was observed in fish exposed to sediment from an industrial site. A significant reduction in primary spermatocyte accumulation was observed in the exposed group compared with that in the control group, and some individuals exposed to sediments from industrial sites presented with testis–ova. Our results suggest that Uruguay River sediments act as an important source of estrogenic compounds that could be responsible for the alterations observed. Future studies are needed to identify the causal agents and determine exposure routes.

En Uruguay el incremento sostenido de los cultivos de soja (Glycine max) en los últimos años ha perjudicado a la industria apícola al desplazar a otros cultivos, por ejemplo las leguminosas forrajeras. Aunque la soja es una especie autógama, algunos estudios señalan que la producción de semillas puede incrementarse con insectos polinizadores, especialmente con abejas melíferas (Apis mellifera). El objetivo de este estudio fue determinar si las abejas melíferas y otros insectos incrementan la producción de semillas en un cultivo de soja convencional. Para ello se instaló un apiario de 10 colmenas en una parcela de 120 ha de soja. Se registró la presencia de abejas y otros insectos a diferentes distancias del apiario evaluando la producción de semillas a 200 y 500 m. En las colmenas se determinó el origen botánico del néctar y el polen que colectaron las abejas. Los principales resultados encontrados fueron: 1) Las abejas no se distribuyeron en el cultivo siguiendo un gradiente con la distancia al apiario. 2) Las abejas colectaron néctar y polen de las flores de soja, aunque la planta tendría un mayor valor nectarífero que polinífero. 3) La producción de semillas se incrementó significativamente un 25% a 500 m del apiario, pero no a 200 m. Esta diferencia pudo deberse a distintas concentraciones de nitrógeno y potasio en el suelo. Este estudio muestra que la producción de semillas de soja puede incrementarse en presencia de abejas melíferas abriendo una perspectiva para la complementación de la producción sojera y apícola In Uruguay, the sustained increase of soybean (Glycine max) crop in recent years has harmed the bee industry because it displaced other crops such as forage legumes. Although soybean is a self-pollinating species, some studies indicate that seed production can be increased by insect pollinators, especially honey bees (Apis mellifera). The aim of this study was to determine whether honey bees and other insects increase seed production in conventional soybean.To do it, an apiary of 10 hives was set in a plot of 120 ha of soybean. We recorded the presence of bees and other insects at different distances from the apiary and seed production was evaluated at 200 and 500 m. In the hives, we determined the botanical origin of nectar and pollen collected by bees. The principal results were: 1) bees were not distributed in the crop following a gradient with distance from the apiary. 2) bees collected nectar and pollen from flowers of soybean, although the plant provides more nectar than pollen.3) seed production increased significantly by 25% at 500 m of the apiary, but not at 200 m. This difference could be due to different concentrations of nitrogen and potassium in the soil. This study shows that soybean production can be increased in the presence of honeybees opening a perspective for the complementation of soybean production and beekeeping

Este trabajo estudio la toxicidad aguda por contacto del acido oxalico (AO) sobre una subespecie poli-hibrida de abejas (Apis mellifera), la cual es el biotipo dominante en la zona sudoeste de Uruguay (SWZU), la region mas importante para la produccion de miel en este pais. Este estudio determino la dosis letal 50 (DL50), asi como el nivel de efecto no observado (NOEL), el nivel de efecto minimo observado (LOEL), y el numero total de individuos por colmena. El proposito fue evaluar la relacion entre la dosis maxima de AO usada en Uruguay (3.1 g AO por colmena) y los parametros toxicologicos de las abejas de la SWZU. Los resultados mostraron que es posible elevar la dosis actual de AO por colmena a 9.3 g, ya que la dosis actual de 3.1 g de AO corresponde a 132.8 AO por abeja, y el NOEL determinado es 400 AO por abeja. Los resultados tambien destacaron algunas diferencias entre la DL50 de las abejas del SWZU (548.95 AO por abeja) y algunos valores de DL50 publicados para otras subespecies de abejas.

The implementation of eco-toxicological assessment in South America is presently limited due to significant scientific information gaps concerning native species and their potential use as biomarkers. Recently, a common southern hemisphere fish species, Astyanax fasciatus, has been pointed out as a potential bio-indicator to anthropogenic pollution. This is a small, abundant, Neotropical characid, which is widely distributed from Central America south, to the Rio de la Plata Basin of western Uruguay. Our study found a statistically significant increase of coproporphyrin, uroporphyrin and protoporphyrin concentrations in hepatic tissues of A. fasciatus collected from a stream segment with high anthropogenic disturbance (due mainly to agricultural derivatives and motor vehicle transportation activities). Although the area studied showed differences in up and downstream limno-chemical parameters, these differences were not related to the increase of hepatic porphyrin concentrations. Based on the results of our study, we conclude that A. fasciatus is a good bio-indicator of exposure to environmental contaminants, and we propose that this abundant fish species be considered as a sentinel organism for monitoring potential disturbances to freshwater ecosystems.

The land cover change of Uruguayan Forestal Plan provoked biogeochemical changes on horizon Au(1) of Argiudols; in native prairies which were replaced by monoculture Eucalyptus sp. plantation with 20 year rotations as trees. Five fields forested and six natural prairies were compared. The results not only show a statistical significant soil acidification, diminution of soil organic carbon, increase of aliphaticity degree of humic substances, and increase of affinity and capacity of hydrolytic activity from soil microbial communities for forested sites with Eucalyptus sp. but also, a tendency of podzolization and/or mineralization by this kind of land cover changes, with a net soil organic lost of 16.6 tons ha(-1) in the horizon Au(1) of soil under Eucalyptus sp. plantation compared with prairie. Besides, these results point out the necessity of correction of the methodology used by assigned Uruguayan commission to assess the national net emission of greenhouse gases, since the mineralization and/or podzolization process detected in forested soil imply a overestimation of soil organic carbon. The biochemical parameters show a statistical significant correlation between the soil organic carbon status and these parameters which were presented as essential for the correct evaluation of Uruguayan soil carbon sink.