CONSERVB: A numerical method to compute soil water content and temperature profiles under a bare surface

A comprehensive, yet fairly simple model of water disposition in a bare soil profile under the sequential impact of rain storms and other atmospheric influences, as they occur from hour to hour is presented. This model is intended mostly to support field studies of soil moisture dynamics by our current team, to serve as a background for the microwave measurements, and, eventually, to serve as a point of departure for soil moisture predictions for estimates based in part upon airborne measurements. The main distinction of the current model is that it accounts not only for the moisture flow in the soil-atmosphere system, but also for the energy flow and, hence, calculates system temperatures. Also, the model is of a dynamic nature, capable of supporting any required degree of resolution in time and space. Much critical testing of the sample is needed before the complexities of the hydrology of a vegetated surface can be related meaningfully to microwave observations

Forage Quality and the Environment

The influence of environmental factors on forage quality of temperate and tropical grasses has been reviewed by several authors, who summarized how light, temperature, drought and soil nutrients influence chemical composition, and digestibility of forages grown in contrasting areas of the world. The effects of season of the year on forage growth, grazing behavior and animal performance have also been the subject of numerous papers and reviews. However, there are few recent reviews that summarize how changes in climatic and edaphic factors influence forage quality of legumes with variable levels of condensed tannins (CT), which are important secondary compounds in some temperate and tropical legume species adapted to acid infertile soils. In this paper we summarize properties of CT and their positive and negative effects on forage quality of legumes. We also review published work on the effect of temperature, drought, CO2 concentration, season of the year and soil fertility on the accumulation of CT in temperate and tropical legumes. Results from experiments under controlled conditions indicate that high temperature alone can significantly increase the accumulation of CT in some temperate legume species (i.e. Lotus pedunculatus) but not in others (i.e. L. corniculatus). However, the effect of low or high temperature on accumulation of CT is considerably greater when accompanied with other environmental factors such as drought, high CO2 concentration and soil nutrient deficiencies. Soil nutrient deficiencies can have a major effect on elevation of CT concentration and overall feed value of temperate and tropical legumes, but only when deficiencies are such that they affect plant growth. Soil fertility and climatic conditions affect not only the concentration of CT but also their monomer composition and MW (molecular weight), as was observed in a tropical legume species well adapted to acid infertile soils. The nutritional significance of these findings are not all that well understood, but it would seem that CT in forage legumes are not a uniform chemical entity given that they can change with edaphic and climatic factors. Finally we suggest that there is a need to investigate alternatives to enhance the feed value of legumes with tannins adapted to acid soils through selection of genotypes with less CT and /or through manipulation of environmental factors such as soil fertility. For this we need to better understand how edaphic and climatic factors affect not only accumulation of CT but also their chemical structure and biological activity and relate these changes to forage intake, digestibility, N utilization, and, ultimately, to performance of ruminant animals

Adoption of \u3ci\u3eBrachiaria\u3c/i\u3e Grasses in Mexico and Central America: A Successful Story

In Latin America and the Caribbean (LAC) there has been a major effort to develop new pastures technologies, to increase livestock productivity for the extensive systems prevailing in the tropical lowlands. This multi-national and inter-institutional effort was initiated through the International Network for the Evaluation of Tropical Pastures (RIEPT, by its name in Spanish), which operated from 1976 to 1996 under CIAT leadership. This network became a platform for institutions to train technicians, share forage material from existing gene banks, study the behaviour of new germplasm under different environments, and established the exchange of scientific information to extrapolate research results (Toledo, 1982). Six hundred and forty five agronomists from 24 countries in LAC were trained by RIEPT, in subjects related to forage agronomy and pasture evaluation. Training was key for the success of RIEPT, because these professionals carried out evaluations of new and improved forages under contrasting ecosystems and provided feedback. In addition, during this period participating institutions in RIEPT released 11 selected grasses as commercial cultivars, most of them from the Brachiaria genus, as well as 16 forage legume cultivars (CIAT, 2003). In Central America and Mexico these cultivars were released between 1990 and 1996. Forage evaluation activities in this region continues at present through a joint research agenda between CIAT and ILRI, as well as between CIAT and the private seed sector. Of all pasture cultivars released; grasses from the Brachiaria genus currently dominate the market – accounting for approximately 84% of all grass seed sales in Mexico and Honduras, 90% in Nicaragua, 85% in Costa Rica, and 97% in Panama during the last 5 years (Holmann et al., 2004). The objective of this paper is to estimate the impact of the adoption of Brachiaria grasses released through RIEPT during the period 1990-2003 on milk and beef production and to describe how this was achieved

Evaluation of \u3ci\u3ePaspalum\u3c/i\u3e spp. with Adaptation to Poorly Drained Soils in the Tropical Americas

A collection of Paspalum accessions obtained from Brazil was tested for their adaptation to poorly drained soils. Three accessions were selected based on their DM production and nutritive value. Productivity and quality of these three accessions was stable over the periods of maximum and minimum rainfall, giving potential for continuous forage supply throughout the year in the tropical Americas. Grazing trials for the selected accessions are underway

Investigation of remote sensing techniques of measuring soil moisture

Major activities described include development and evaluation of theoretical models that describe both active and passive microwave sensing of soil moisture, the evaluation of these models for their applicability, the execution of a controlled field experiment during which passive microwave measurements were acquired to validate these models, and evaluation of previously acquired aircraft microwave measurements. The development of a root zone soil water and soil temperature profile model and the calibration and evaluation of gamma ray attenuation probes for measuring soil moisture profiles are considered. The analysis of spatial variability of soil information as related to remote sensing is discussed as well as the implementation of an instrumented field site for acquisition of soil moisture and meteorologic information for use in validating the soil water profile and soil temperature profile models

El principismo argentino ante la Primera Guerra Mundial

Hasta la primera guerra mundial de 1914-1918, la humanidad no había presenciado un cataclismo bélico de tal magnitud. Resultó lógico que esa situación trastocara todas las normas del derecho internacional, las relaciones entre los pueblos y la convivencia política económica del mundo entero. La Argentina no estuvo al margen de tales acontecimientos y transformaciones y, aunque adoptara una posición neutralista que la apartó del contexto beligerante, no quedó fuera de la comunidad internacional y, esa misma posición, le otorgó singular prestancia para definir cuestiones principistas que han quedado como una lección pacifista, ansiosa de la justicia, la tolerancia y la hermandad entre los pueblos y los hombres. Para estudiar la situación argentina frente a la Gran Guerra necesitamos bucear en los antecedentes inmediatos al conflicto y en los intereses europeos que allí se pusieron de manifiesto

Detecting bacterial endophytes in tropical grasses of the Brachiaria genus and determining their role in improving plant growth

Plant-growth-promoting (PGP) bacteria include a diverse group of soil bacteria thought to stimulate plant growth by various mechanisms. Brachiaria forage grasses, of African origin, are perennials that often grow under low-input conditions and are likely to harbour unique populations of PGP bacteria. Three bacterial strains that tested positive for nitrogenase reductase gene sequences (nifH) were isolated from Brachiaria hybrid CIAT 36062 and introduced into Brachiaria hybrid cv. Mulato, which also had indigenous endophytic bacteria testing positive for nifH gene sequences. Under conditions of nutrient deficiency, inoculated Mulato plants had significantly higher biomass production, chlorophyll and total nitrogen contents in leaves than do control plants and were darker green. Strains ofendophytic bacteria were then artificially introduced into Brachiaria  brizantha CIAT 6294, which does not have indigenous endophytic bacteria. Results were consistent with those obtained with artificially inoculated Mulato plants, suggesting that these endophytic bacteria do benefit plant growth. DNA sequence analysis demonstrated that the nifH gene sequences were highly similar to those from Klebsiella pneumoniae and other N2-fixing organisms and that the nif genes had consensus  sequences identical to those of other N2-fixing bacteria.Key words: Bacterial endophytes, green fluorescent protein, nitrogenase reductase, plant growth-promoting bacteria, Brachiaria

Antecedentes para una historia del hombre santiagueño en la región chaqueña

Santiago de Estero se proyecta desde lo más remoto de nuestro pasado histórico como un cofre que guarda las puras esencias del alma tradicional argentina. Una inmensa llanura enclavada en el centro del mediterráneo del viejo país confiere notable uniformidad al relieve, y hace de estatierra un verdadero corredor interpuesto entre el litoral y el norte en una mole geográfica, cuya valoración trasciendesus linderos territoriales."Por mucho mayor que sea cuantitativamente la importancia de esas dos regiones -ha escrito Bernardo Canal Feijóo- no podrá dejar de ser relativa, mientras éstas no pueden prescindir de Santiago; y el problema consiste, precisamente en que, por sus masas y su ubicación, Santiago es para esas dos regiones imprescindible o inevitable".Academia Nacional de Agronomía y Veterinaria (ANAV

Los cementos de ionómero vítreo de alta viscosidad para el éxito del tratamiento restaurador atraumático.

Objetivo: Evaluar mediante un estudio in vitro las propiedades: Resistencia Compresiva (RC), Resistencia Flexural (RF), Resistencia al Desgaste (RD), Rugosidad Superficial (RS), Dureza Vickers (HV) y Remineralizacion de los Tejidos Adyacentes (RTA), de diversos CIV de alta viscosidad usados en el TRA con diversos materiales de recubrimiento superficial. Materiales y Métodos: Se analizaron 5 CIV: EQUIA FIL, Fuji IX, Ketac Molar Easymix, Ionofil Molar, Vitremer, combinados con diferentes recubrimientos superficiales: G-Coat Plus, Adper Single Bond y vaselina solida. Las muestras se prepararon segun instrucciones del fabricante. La superficie expuesta del CIV se protegio con materiales de recubrimiento segun cada grupo y cada ensayo y se almacenaron en agua desionizada a 37oC. La RC y RF se midieron con una maquina universal de ensayos (Diggimes). La RD se realizo con un simulador (CFW-07 Software: version 3.XX 0899.3360 S/4). La RS fue evaluada con microscopio Laser Confocal (Olympus LEXT4000). Se midio HV con Microindentador LECO Corporation, Modelo LM-247AT. Para la RTA se utilizo el SEM (Carl Zeizz). Los resultados fueron sometidos a pruebas de ANOVA y Tukey para comparar las diferencias entre grupos. Resultados: Los valores mas altos para RC se registraron para V y KM con vaselina (95,43MPay 78,15 MPa respectivamente); para RF, V (80,75MPa) seguido de los materiales con recubrimientos superficiales G-Coat Plus y Adper Single Bond (entre 54,19 y 64,71 MPa); el menor desgaste fue el EF (0,34mg); la menor Ra fue para KM, IM, EF (0.16, 0.23 y 0.29μm respectivamente) ; la mayor HV fue para EF (110,6 HV) seguido por KM con Adper Single Bond (104,2 HV); los materiales que liberaron mayor cantidad de F y Sr fueron respectivamente: EF (media: 342,9) y KM (media: 394,5). Conclusión: El efecto del recubrimiento superficial no mostro diferencia significativa para la RC ni para la RD pero si para la RF, HV donde los valores mas altos se registraron en los grupos con proteccion. No existe un solo material que reuna las mejores propiedades para aplicarlo en TRA, pero EF y KM fueron los cementos que alcanzaron el mejor desempeno en este estudio en concordancia con los reportes de estudios clinicos recientes

Condensed Tannins in Tropical Legumes: Concentration, Astringency and Effects on the Nutrition of Ruminants

A feeding trial was carried out to determine the effect of extractable condensed tannins (ECT) concentration and tannin astringency in tropical legumes on nitrogen (N) digestion by sheep. Test legumes were Desmodium ovalifolium (Do) and Flemingia macrophylla (Fm) which had similar concentrations of Extractable CT (9% DM) but tannins with different degree of astringency (Do, 0.6 and Fm, 0.3 g protein bound/g of ECT). Chopped sun-dried forage of each legume was sprayed with either water (control) or polyethylene glycol (PEG, 3.5% DM) to reduce ECT and fed to 8 sheep with ruminal and duodenal canulas arranged in a replicated 4 x 4 Latin Square changeover design. Greater (P\u3c0.05) N flow to duodenum, and fecal N were observed with Fm than with Do. Estimates of escape N were similar (58 to 61%) for both legumes. Reduction of ECT with PEG in both legumes (9.0-9.4 to 4.7-5.4%) resulted in lower (P\u3c0.05) proportion of N reaching the duodenum. Results indicate that concentration of ECT had a greater effect on N digestion by sheep than tannin astringency