AGGREGATE STABILITY AND WATER RETENTION NEAR SATURATION CHARACTERISTICS AS AFFECTED BY SOIL TEXTURE, AGGREGATE SIZE AND POLYACRYLAMIDE APPLICATION

Understanding the effects of soil intrinsic properties and extrinsic conditions on aggregate stability is essential for the development of effective soil and water conservation practices. Our objective was to evaluate the combined role of soil texture, aggregate size and application of a stabilizing agent on aggregate and structure stability indices (composite structure index [SI], the and n parameters of the VG model and the S-index) by employing the high energy (0-5.0 J kg(-1)) moisture characteristic (HEMC) method. We used aggregates of three sizes (0.25-0.5, 0.5-1.0 and 1.0-2.0 mm) from four semi-arid soils treated with polyacrylamide (PAM). An increase in SI was associated with the increase in clay content, aggregate size and PAM application. The value of increased with the increase in aggregate size and with PAM application but was not affected by soil texture. For each aggregate size, a unique exponential type relationship existed between SI and . The value of n and the S-index tended, generally, to decrease with the increase in PAM application; however, an increase in aggregate size had an inconsistent effect on these two indices. The relationship between SI and n or the S-index could not be generalized. Our results suggest that (i) the effects of PAM on aggregate stability are not trivial, and its application as a soil conservation tool should consider field soil condition, and (ii), n and S-index cannot replace the SI as a solid measure for aggregate stability and soil structure firmness when assessing soil conservation practices

Assessing Romanian financial sector stability: the importance of the international economic climate

The aim of this paper is to develop an aggregate stability index for the Romanian financial system. The index which is meant to enhance the set of analysis used by the central bank to assess the financial stability accurately reflects the financial stability dynamics and the periods with financial turbulences during 1997-2007 in Romania. By the application of a technique which enables the measurement of the components’ contribution to the aggregate index volatility, we show that some individual stability indicators require a close monitoring by the authorities in order to detect the instability periods. Several attempts to set up a financial stability aggregate index can be found in the literature, but none of these studies took into consideration the spillover effect between different financial markets. One of the contributions of our paper is the introduction within the aggregate index of an indicator capable of highlighting the international economic climate. The deterioration of the world economic climate can represent the background for the contagion phenomenon. The outcome of the study shows an improvement of the Romanian financial stability during the analysed period. The aggregate index volatility also decreased starting with 1999. The financial vulnerability and financial soundness indicators have a significant contribution to the volatility of the aggregate index in the periods foregoing the crisis appearance. On the contrary, the volatility of the world economic climate indicators is reduced before the crisis, rising immediately after its burst out.financial stability, quantitative methods for assessing systemic stability, aggregate financial stability index, world economic climate index

Aggregate Price Shocks and Financial Instability: An Historical Analysis

This paper presents empirical evidence on the hypothesis that aggregate price disturbances cause or worsen financial instability. We construct two annual indexes of financial conditions for the United States covering 1790-1997, and estimate the effect of aggregate price shocks on each index using a dynamic ordered probit model. We find that price level shocks contributed to financial instability during 1790-1933, and that inflation rate shocks contributed to financial instability during 1980-97. Our research indicates that the size of the aggregate price shocks needed to substantially alter financial conditions depends on the institutional environment, but that a monetary policy focused on price stability would be conducive to financial stability.

Aggregate Price Shocks and Financial Instability: An Historical Analysis

This paper presents empirical evidence on the hypothesis that aggregate price disturbances cause or worsen financial instability. We construct two annual indexes of financial conditions for the United States covering 1790-1997, and estimate the effect of aggregate price shocks on each index using a dynamic ordered probit model. We find that price level shocks contributed to financial instability during 1790-1933, and that inflation rate shocks contributed to financial instability during 1980-97. Our research indicates that the size of the aggregate price shocks needed to substantially alter financial conditions depends on the institutional environment, but that a monetary policy focused on price stability would be conducive to financial stability.

A dynamic econometric study of income, energy and exports in Turkey

This study attempts to examine empirically dynamic causal relationships between aggregate output, energy consumption, exports, capital and labour in the case of Turkey using the time series data for the period 1968-2008. This research tests the interrelationships between the variables using the bounds testing to cointegration procedure. The bounds test results indicate that there exists a long-run relationship between the variables in which the dependent variable is aggregate output. Within this study, three competing sets of hypotheses regarding the relationship between aggregate output, exports and energy consumption are tested. An augmented form of Granger causality analysis is conducted amongst the variables. In the long-run, causality runs interactively through the error correction term from labour, capital, exports and energy consumption to aggregate output. In the short-run, two important bilateral causalities were identified: between energy consumption and aggregate output, between exports and aggregate output. The short-run causality testing reveals further the existence of a unilateral causality running from exports to energy consumption too. The long-run relationship of aggregate output, energy consumption, exports, capital and labour equation is also checked for the parameter stability. The results also provide some important policy recommendations.Aggregate output; energy consumption; capital; labour; cointegration; Granger causality; stability tests; Turkey

Unequal Spending, Aggregate Demand and International Financial Stability

Währungskrise, Ausgaben, Gesamtwirtschaftliche Nachfrage, Preisniveaustabilität, Vereinigte Staaten, Currency crisis, Expenditure, Aggregate demand, Price stability, United States

Site-Specific Conditions Change the Response of Bacterial Producers of Soil Structure-Stabilizing Agents Such as Exopolysaccarides and Lipopolysaccarides to Tillage Intensity

Agro-ecosystems experience huge losses of land every year due to soil erosion induced by poor agricultural practices such as intensive tillage. Erosion can be minimized by the presence of stable soil aggregates, the formation of which can be promoted by bacteria. Some of these microorganisms have the ability to produce exopolysaccharides and lipopolysaccharides that "glue" soil particles together. However, little is known about the influence of tillage intensity on the bacterial potential to produce these polysaccharides, even though more stable soil aggregates are usually observed under less intense tillage. As the effects of tillage intensity on soil aggregate stability may vary between sites, we hypothesized that the response of polysaccharide-producing bacteria to tillage intensity is also determined by site-specific conditions. To investigate this, we performed a high-throughput shotgun sequencing of DNA extracted from conventionally and reduced tilled soils from three tillage system field trials characterized by different soil parameters. While we confirmed that the impact of tillage intensity on soil aggregates is site-specific, we could connect improved aggregate stability with increased absolute abundance of genes involved in the production of exopolysaccharides and lipopolysaccharides. The potential to produce polysaccharides was generally promoted under reduced tillage due to the increased microbial biomass. We also found that the response of most potential producers of polysaccharides to tillage was site-specific, e.g., Oxalobacteraceae had higher potential to produce polysaccharides under reduced tillage at one site, and showed the opposite response at another site. However, the response of some potential producers of polysaccharides to tillage did not depend on site characteristics, but rather on their taxonomic affiliation, i.e., all members of Actinobacteria that responded to tillage intensity had higher potential for exopolysaccharide and lipopolysaccharide production specifically under reduced tillage. This could be especially crucial for aggregate stability, as polysaccharides produced by different taxa have different "gluing" efficiency. Overall, our data indicate that tillage intensity could affect aggregate stability by both influencing the absolute abundance of genes involved in the production of exopolysaccharides and lipopolysaccharides, as well as by inducing shifts in the community of potential polysaccharide producers. The effects of tillage intensity depend mostly on site-specific conditions

Assessment of selected soil parameters in a long-term Western Canadian organic field experiment

A long-term field study was used to compare soil nitrogen and phosphorous status, and soil aggregate stability in organic and conventional cropping systems. Two rotations were tested: a grain only and a grain-alfalfa hay rotation. The organic systems had a lower nitrate leaching potential than the same rotations under conventional management. After 13 years, one organic system (the grain-alfalfa; no manure return) is suffering serious soil P depletion. However, the grain only and the grain-alfalfa with manure return to land systems had soil P levels similar to the prairie grass control treatment and showed no signs of P deficiency. Despite having lower levels of organic carbon, the organic soils had higher levels of wet aggregate stability than conventionally managed soils

Measuring Forecast Uncertainty by Disagreement: The Missing Link

Using a standard decomposition of forecasts errors into common and idiosyncratic shocks, we show that aggregate forecast uncertainty can be expressed as the disagreement among the forecasters plus the perceived variability of future aggregate shocks. Thus, the reliability of disagreement as a proxy for uncertainty will be determined by the stability of the forecasting environment, and the length of the forecast horizon. Using density forecasts from the Survey of Professional Forecasters, we find direct evidence in support of our hypothesis. Our results support the use of GARCH-type models, rather than the ex post squared errors in consensus forecasts, to estimate the ex ante variability of aggregate shocks as a component of aggregate uncertainty.