Effect of Native Grassland Intensification over Cattle Performance

The objective was to evaluate the effect of different levels of intensification in native grassland over cattle live weight gain (LWG), stocking rate (SR) and average daily gain (ADG) in Uruguay. The study was carried out in 7.8 ha in Paysandú, between winter 2015 and autumn 2019. Experiment was a randomized complete block design, with 4 replicates. The four treatments applied were native grassland (NG), NG overseeded with Trifolium pratense (6 kg.ha-1) and Lotus tenuis (6 kg.ha-1) + 40 kg.ha-1 of P2O5 (NGO), NG fertilized with 60 kg.ha-1 of N + 40 kg.ha-1 of P2O5 (N60) and NG fertilized with 120 kg.ha-1 of N + 40 kg.ha-1 of P2O5 (N120). Fertilizers used were urea and a blend of 7-40/40-0-4. Animals were growing Holstein steers, with initial live weight of 180 ± 22 kg. Treatments management consisted of rotational stocking system, subdivided in 4 plots, according to blocks. Grazing periods were 14 ±1 day, and rest periods were 45 ±2 days, totaling a grazing cycle of 60 days. The average area of the plots of NG and NGO treatments was 0.72 ha while the treatments of N60 and N120 was 0.26 ha. The SR was significantly different between treatments (P = 0.066). The SR in N60 was 868 ±85 kg LW.ha-1, in N120 was 856 ±124 kg LW.ha-1, in NGO was 583 ±91 kg LW.ha-1 and in NG 544 ±40 kg LW.ha-1. The ADG was not different between treatments (P = 0.372), averaging 0.472 kg LW.animal-1.day-1. The LWG was different between treatments (P = 0.050). The LWG was higher in N60 (432 ±107 kg LW.ha-1.year-1), intermediate in N120 (391 ±91 kg LW.ha-1.year-1) and NGO (306 ±148 kg LW.ha-1.year-1) and lower in NG (206 ±63 kg LW.ha-1.year-1). Increasing levels of intensification in native grassland allow higher ADG and SR, determining higher LWG

Changes in Defoliation Patterns of Plant Functional Groups under Variable Herbage Allowance in Campos Grasslands

Several studies have evaluated separately forage production, botanical composition, leaf traits and animal performance. However, few of them have focused on defoliation patterns at the level of functional groups (FGs) under different and variable herbage allowance (HA), especially in natural, diverse grasslands. The objective was to evaluate the relationship between HA and leaf traits on defoliation patterns of mature beef cows in the autumn, winter and spring. We evaluated the grazing probability (GP), intensity of defoliation (ID), and leaf traits on 14 species that represent more than 80% of total dry matter of the pasture. The experiment at which we evaluated those traits and responses has been managed under High HA (HHA) and Low HA (LHA) (8 and 5 kg dry matter kg live weight-1, respectively). Four plant FGs (A, B, C and D) were defined according to leaf traits, and a selectivity index (SI) was developed for each group (considering the proportion of grazed and ungrazed species). Grazing patterns shifted across seasons. In the autumn, grazing was concentrated on FGs A, B and C groups (GP = 0.417). While for FG D, represented by high-biomass tussocks, the GP was lower (0.075). During winter, when herbage accumulation rate is limited, the average GP was 0.175. FGs C and D were more defoliated in relation to autumn, and during spring the GP shifted to FG B (0.289). The ID was similar to all FGs and seasons (66 % of leaf removed). In autumn and spring, the SI was affected by FGs and HA while in winter were similar between FGs but higher in HHA. Cows behaved differently in the defoliation pattern, modifying mainly the GP on FGs rather than the ID. Variation in HA across season determined changes in defoliation pattern, allowing to express selectivity in autumn and spring

The soft x-ray instrument for materials studies at the linac coherent light source x-ray free-electron laser

This content may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This material originally appeared in Review of Scientific Instruments 83, 043107 (2012) and may be found at https://doi.org/10.1063/1.3698294.The soft x-ray materials science instrument is the second operational beamline at the linac coherent light source x-ray free electron laser. The instrument operates with a photon energy range of 480–2000 eV and features a grating monochromator as well as bendable refocusing mirrors. A broad range of experimental stations may be installed to study diverse scientific topics such as: ultrafast chemistry, surface science, highly correlated electron systems, matter under extreme conditions, and laboratory astrophysics. Preliminary commissioning results are presented including the first soft x-ray single-shot energy spectrum from a free electron laser

Evolução de CO2 e atividades enzimáticas em amostras de solo tratado com herbicidas

Os efeitos dos herbicidas bentazon, metolachlor, trifluralin, imazethapyr, imazethapyr+lactofen, haloxyfop-methyl, glyphosate e chlorimuron-ethyl, testados em duas concentrações (duas e dez vezes a dose média recomendada por hectare), sobre a atividade microbiana foram estudados em amostras de solo que nunca haviam recebido tratamento com pesticidas. Como bioindicadores, utilizou-se a respiração microbiana, quantificando a emissão de CO2 aos 2, 4, 8, 12, 16, 20 e 24 dias após incubação, a atividade da enzima desidrogenase e a hidrólise de diacetato de fluoresceína (FDA), aos 8 e 28 dias. Bentazon e a mistura de imazethapyr+lactofen na maior concentração e o haloxyfop-methyl nas duas concentrações apresentaram efeitos inibitórios na respiração edáfica, embora diferentes em época e duração do efeito. Nenhum dos tratamentos herbicidas afetou a hidrólise da FDA. A atividade da desidrogenase foi inibida, o que foi verificado em análise realizada aos oito dias,nas amostras de solo com alta concentração de bentazon e imazethapyr; no entanto, foi estimulada nos tratamentos com baixa concentração de metolachlor e imazethapyr e na maior concentração de glyphosate. A respiração basal e a atividade da desidrogenase mostraram maior sensibilidade na detecção de efeitos dos herbicidas sobre a microbiota do solo que as determinações da hidrólise de FDA. Apenas foi encontrada correlação significativa entre a atividade da desidrogenase e a respiração basal aos oito dias de incubação. Os resultados destacam a importância da consideração de múltiplos indicadores na avaliação dos efeitos de herbicidas na microbiota do solo

Soil sampling depth and phosphorus extraction method for phosphorus in leguminous pastures.[Profundidad de muestreo del suelo y método de extracción de fósforo en pasturas de leguminosas].[Profundidade de amostragem e método de extração de fósforo em solos com pastagens de leguminosas].

Abstract: The current guidelines and recommendations for P fertilization in Uruguay can be improved by adjusting the sampling depth and analytical methods of testing soil P in pastures with different fertilization history. A set of field trials was con-ducted between2008 and 2012 on 14 sites of Uruguay for the purpose of comparing two sampling depths and three methods for assessing P availability by their correlation with annual dry matter yield response. The trials had a randomized complete block design and were sown with Trifolium repensor Lotus corniculatus. Soil P availability was determined by sampling 0-7.5 and 0-15 cmdepth using three analytical methods: Bray I, cationic resins, and citric acid. Rock phosphate and triple superphosphate were applied at five P rates. (0-240 kg kg P2O5 ha-1).Annual forage yield was recorded. Relative yield was calculated as measured yield/maximum yield observed within a block. The correlation between relative yield and soil P availability was studied using the modified arcsine-logarithm calibration curve (ALCC) and analyzing the resulting correlation coefficient, root-mean-square error (RMSE) of the soil P test, and RMSE of the relative yield. The 0-7.5 cm soil sampling depth did not show a better fit than the deeper sampling (0-15 cm), with the latter having less variation in soil P test values. When rock phosphate was used, the correlation coefficients were 0.50 for cationic resins, 0.53 for citric acid,and 0.38 for Bray I. When triple superphosphate was used, the correlation coefficients were 0.37 for cationic resins, 0.44 for citric acid and 0.43 for Bray I. For both P sources, the citric acid method withthe sampling of0-15 cm soil depth is the preferred soil P test method for management of P in leguminous pastures for the soils studied.Resumen:En Uruguay, se reconoce que las pautas y las recomendaciones vigentes para la fertilización fosfatada de pasturaspue-den mejorarse a través de un ajuste de la profundidad de muestreo y los métodos analíticos para determinar el fósforo (P) extractable en suelo. El objetivo de este trabajo fue comparar dos profundidades de muestreo y tres métodos de extracción de P en suelo, a través de su correlación con la respuesta vegetal. Los experimentos fueron realizados entre los años 2008 y 2012, en 14 sitios de Uruguay, sobre pasturas de Trifolium repensy Lotus corniculatusfertilizadas con roca fosfórica y superfosfato triple. Se determinó anualmente la disponibilidad de P en el suelo a 0-7,5 y 0-15 cm de profundidad, con tres métodos analíticos: Bray I, resinas catiónicas y ácido cítrico. Se midió anualmente el rendimiento de forraje. La profundidad de muestreo del suelo 0-7,5 cm no mostró un mejor ajuste que el muestreo más profundo (0-15 cm), teniendo este último una menor variación en los valores de análisis de suelo. Cuando se usó roca fosfórica, los coeficientes de correlación fueron 0,50 para resinas catiónicas, 0,53 para ácido cítrico y 0,38 para Bray I. Cuando se usó superfosfato triple, los coeficientes de correlación fueron 0,37 para resinas catiónicas, 0,44 para ácido cítrico y 0,43 para Bray I. Para ambas fuentes de P, el método de ácido cítrico, con muestreo de 0-15 cm de profundidad, es el que mejor se ajusta en la determinación del P extractable, para el conjunto de los suelos evaluados.Resumo:No Uruguai, é reconhecido que os parâmetros e recomendações vigentes para a fertilização fosfatada de pastagens podem ser aprimoradas através de um ajuste da profundidade de amostragem e dos métodos analíticos para determinar fósforo (P) extraível do solo. O objetivo deste trabalhofoi comparar duas profundidades de amostragem e três métodos de extração de P do solo e correlacionar com a resposta vegetal. Os experimentos foram realizados entre os anos de 2008 e 2012, em 14 campos de Uruguai, sobre pastagens formadas por Trifolium repense Lotus corniculatus, fertilizadas com rocha fosfatada e superfosfato triplo. Anualmente foi determinada a disponibilidade de P em diferentes profundidades do solo, 0-7,5 e 0-15 cm, com três métodos de analíticos: Bray I, resinas catiônicas e ácido cítrico; além do rendimento de forragem. A profundidade de amostragem do solo de 0-7,5 cm não mostrou melhor correlação com a resposta vegetal na comparação com amostragem mais profunda (0-15 cm), apresentando esta última menor variação nos valores das análises de solo. Quando foi usado rocha fosfatada, os coeficientes de correlação foram 0.50 para resina catiônica, 0.53 para acido cítrico e 0.38 para Bray I. Entretanto, quando usado superfosfato triplo, os coeficientes de correlação foram 0.37, 0.44 e 0.43 para os métodos de resina catiônica, acido cítrico e Bray I, respectivamente. Para ambas as fontes de P o método de acido cítrico, com amostragem de 0-15 cm de profundidade, foi o que melhor se ajustou a determinação de P extraível, em os solos avaliados

Cost and environmental analyses of reinforcement alternatives for a concrete bridge

Reinforced Concrete (RC) and Prestressed Concrete (PC) structures using conventional materials in aggressive exposure conditions are susceptible to corrosion. Non-corrosive reinforcement materials such as: Glass Fiber-Reinforced Polymer (GFRP) rebars; Carbon Fiber-Reinforced Polymer (CFRP) strands; Stainless-Steel (SS); and Epoxy-coated steel (ECS) reinforcing bars, are attracting attention as more appropriate options in concrete structures. This paper addresses a Life Cycle Cost (LCC) analysis that verifies the cost performance of four different alternative reinforcement bars for the design of a demonstration FRP-RC/PC bridge in Florida, namely Halls River Bridge (HRB). The four different alternatives to be compared are namely Carbon Steel (CS), SS, FRP, and ECS, and the analysis is performed over 100-years. Additionally, a Life-Cycle Assessment (LCA) is included in the analysis to investigate the environmental credentials of the four design alternatives. Cost sensitivity analyses over specific parameters are included. The parameters analyzed are: reinforcement cost, changes in chloride concentration levels over the bridge service life, and discount rate values. Conclusions and recommendations for standard practices and design of future alternative solutions are then presented

Descompactación sub superficial del suelo en sistemas de agricultura continua sin laboreo.

La agricultura continua sin laboreo puede generar condiciones físicas del suelo restrictivas, que limitan el ingreso de agua al suelo y la exploración radicular, generando limitantes para la absorción de agua y nutrientes por las plantas. En Uruguay, los sistemas agrícolas sin laboreo se desarrollaron inicialmente sin esta limitante, ya queutilizaron la rotación de cultivos con pasturas y el tiempo de barbecho como variables de manejo para evitar y manejar problemas de compactación superficial asociados, en la mayoría de los casos, al pisoteo por pastoreo de las pasturas y verdeo

Phosphorus runoff in a non-fertilized soybean production system of SW Uruguay: abstract.

Since 2001/2002 there has been a formidable expansion of annual crops in Uruguay which has determined changes in landuse, with a strong expansion of soybeans (Glycine max) under no-tillage. Improperly managed crop production systems canbe an important nonpoint source of pollution, accelerating eutrophication of surface waters resulting from nitrogen and phosphorus(P) inputs. Nutrient losses depend on many factors such as climate, soil characteristics and management practices. Thus, theobjective of this work was to estimate the annual P loss on a cropping system and to determine the main factors contributingto such losses. Runoff plots were located at the Experimental Station of the National Agricultural Research Institute in Colonia(INIA "La Estanzuela"), Uruguay (34º25´S, 58º0´W) during the period 2013-2014. Plots were under a Vertic Argiudoll soil with18.5 mg/kg P-Bray I on the first 7,5 cm, a 3% slope and available water content of 92.7 mm on the first 56 cm of soil depth. Therotation established was soybean - fallow/cover crop, non-fertilized for over 5 years. The amount of runoff water was measuredfor 23 rainfall events and analyzed for soluble P. During that period the soybean yield was similar to the national average yieldand the annual P loss was 0.5 kg/ha. Available water, precipitation, maximum rainfall intensity and runoff explained most of thevariation in P runoff losses. Rainfall events of high magnitude and intensity on soils with high available water were identified asthe events that produced higher water and P runoff. On the other hand, the model that best fitted P losses was just explained byrainfall and runoff (P = - 9.99 + 0.95*rainfall +21.56*runoff; R2=0.73). Overall, our results indicate that these soybean-covercrop systems under no-tillage, on soils with proper nutrient status and non-fertilized for a long time seem to be economicallyand environmentally adequate management system