Soil degradation: a threat to developing-country food security by 2020?

Global population in the year 2020 will be a third higher than in 1995, but demand for food and fiber will rise by an even higher proportion, as incomes grow, diets diversify, and urbanization accelerates. However this demand is met, population and farming pressure on land resources will intensify greatly. There is growing concern in some quarters that a decline in long-term soil productivity is already seriously limiting food production in the developing world, and that the problem is getting worse. Sarah Sherr first focuses on the magnitude and effects of soil degradation. She then addresses soil degradation in the future and ends her brief with policy and research priorities.Soil degradation Developing countries., Food security Developing countries.,

Laboratory test for EPB tunnelling assessment:results of test campaign on two different granular soils

Earth Pressure Balanced shields are currently the most utilized tunnelling machines throughout around the world. The possibility of using conditioning agents that change the mechanical and hydraulic behaviour of a soil, changing it into a plastic paste and thus permitting soil pressure applications at the tunnel face, is the key point to explain the increasing utilization of this technology. Despite its great importance, not much laboratory researches can be registered on soil conditioning, particularly for cohesionless soils. The conditioning criterion is usually defined on the basis of a trial-and-error procedure developed directly at the job sites. A test that is able to simulate the extraction of soil from the bulk chamber with the screw conveyor inclined upwards, as in real machines, can offer a quantitative indication of the conditioned soil behavior for EPB use. The characteristics of the device and the results obtained on many different types of soil are discussed in order to point out the great importance and quality of results that can be achieved using the proposed test devic

Protein import into chloroplasts: new aspects of a well-known topic

Protein import into plant chloroplasts is a fascinating topic that is being investigated by many research groups. Since the majority of chloroplast proteins are synthesised as precursor proteins in the cytosol, they have to be posttranslationally imported into the organelle. For this purpose, most preproteins are synthesised with an N-terminal presequence, which is both necessary and sufficient for organelle recognition and translocation initiation. The import of preproteins is facilitated by two translocation machineries in the outer and inner envelope of chloroplasts, the Toc and Tic complexes, respectively. Translocation of precursor proteins across the envelope membrane has to be highly regulated to react to the metabolic requirements of the organelle. The aim of this review is to summarise the events that take place at the translocation machineries that are known so far. In addition, we focus in particular on alternative import pathways and the aspect of regulation of protein transport at the outer and inner envelope membrane

Chemical enhancement of soil based footwear impressions on fabric

This study investigates the enhancement of footwear impressions prepared with soils from different locations on a variety of fabric surfaces with different morphology. Preliminary experiments using seventeen techniques were carried out and the best responding reagents were evaluated further. Results indicated that the soils investigated (a cross-section of soils from Scotland) are more likely to respond to reagents that target iron ions rather than calcium, aluminium or phosphorus ions. Furthermore, the concentration of iron and soil pH did not appear to have an effect on the performance of the enhancement techniques. For the techniques tested, colour enhancement was observed on all light coloured substrates while enhancement on dark coloured fabrics, denim and leatherette was limited due to poor contrast with the background. Of the chemical enhancement reagents tested, 2,20-dipyridil was a suitable replacement for the more common enhancement technique using potassium thiocyanate. The main advantages are the use of less toxic and flammable solvents and improved clarity and sharpness of the enhanced impression. The surface morphology of the fabrics did not have a significant effect on the enhancement ability of the reagents apart from a slight tendency for diffusion to occur on less porous fabrics such as polyester and nylon/lycra blends

Prediction of soil available phosphorus based on soil organic carbon

There are many cases in which it is desirable to determine relationships among some soil physical and chemical properties. In soil studies, soil available phosphorous (AP) are often determined using laboratory tests, but it may be more suitable and economical to develop a pedotransfer function which uses some easily available soil properties. In this study, a pedotransfer function for predicting soil AP from soil organic carbon(OC) was suggested and soil AP was estimated as a function of soil OC. The soil AP predicted from the soil AP pedotransfer function was compared to the soil AP determined by laboratory test using the paired samples test and the Bland-Altman approach. The soil AP predicted by the soil AP pedotransfer function was not significantly different from the soil AP determined by laboratory test (P>0.05). The mean difference between the soil AP pedotransfer function and laboratory test was 1.57 ppm (95% confidence interval: -2.88 and 6.03 ppm; P = 0.453). The standard deviation of the soil AP differences was 7.01 ppm. The statistical results of the study indicated that the soil AP pedotransfer function provides an easy, economic and brief methodology to estimate soil AP and in order to predict soil AP based on soil OC the pedotransfer function AP = 0.7927 e 4.9922 OC with R2 = 0.92 can be recommended

Tolerable versus actual soil erosion rates in Europe

Erosion is a major threat to soil resources in Europe, and may impair their ability to deliver a range of ecosystem goods and services. This is reflected by the European Commission's Thematic Strategy for Soil Protection, which recommends an indicator-based approach for monitoring soil erosion. Defined baseline and threshold values are essential for the evaluation of soil monitoring data. Therefore, accurate spatial data on both soil loss and soil genesis are required, especially in the light of predicted changes in climate patterns, notably frequency, seasonal distribution and intensity of precipitation. Rates of soil loss are reported that have been measured, modelled or inferred for most types of soil erosion in a variety of landscapes, by studies across the spectrum of the Earth sciences. Natural rates of soil formation can be used as a basis for setting tolerable soil erosion rates, with soil formation consisting of mineral weathering as well as dust deposition. This paper reviews the concept of tolerable soil erosion and summarises current knowledge on rates of soil formation, which are then compared to rates of soil erosion by known erosion types, for assessment of soil erosion monitoring at the European scale

Assessment of tillage systems in organic farming: influence of soil structure on microbial biomass. First results

Soil tillage modifies environmental conditions of soil microorganisms and their ability to release nitrogen. We compare the influence of reduced tillage (RT) and mouldboard ploughing (MP) on the soil microbial functioning in organic farming. In order to connect soil structure generated by these tillage systems on the soil microbial biomass we adopt a particular sampling scheme based on the morphological characterisation of the soil structure by the description of the soil profile. This method reveals the influence of soil structure on soil microbial biomass and allows a more precise assessment of the impact of tillage managements on the soil microbial functioning

Multiple environmental controls explain global patterns in soil animal communities

Soil animals play important roles in ecosystem functioning and stability, but the environmental controls on their communities are not fully understood. In this study, we compiled a dataset of soil animal communities for which the abundance and body mass of multiple soil animal groups were recorded. The mass–abundance scaling relationships were then used to investigate multiple environmental controls on soil animal community composition. The data reveal latitudinal shifts from high abundances of small soil animals at high latitudes to greater relative abundances of large soil animals at low latitudes. A hierarchical linear mixed effects model was applied to reveal the environmental variables shaping these latitudinal trends. The final hierarchical model identified mean annual temperature, soil pH and soil organic carbon content as key environmental controls explaining global mass–abundance scaling relationships in soil animal communities (R2c = 0.828, Ngroup = 117). Such relationships between soil biota with climate and edaphic conditions have been previously identified for soil microbial, but not soil animal, communities at a global scale. More comprehensive global soil community datasets are needed to better understand the generality of these relationships over a broader range of global ecosystems and soil animal groups

Searching the critical soil organic carbon threshold for satisfactory tilth conditions – test of the Dexter clay:carbon hypothesis

The concern for deteriorating soil structure at low soil organic matter (SOM) contents calls for better knowledge of SOM interaction with soil minerals as well as guidelines for soil conservation. We measured clay dispersibility in a field with a textural gradient. Our results support the concept of differentiating soil content of clay in a complexed and non-complexed part although our data did not point out an exact clay/OC ratio threshold. Our results also indicated that labile fractions of SOM may play an important role in soil physical behavior. We revisited literature data and found evidence that soil content of fines (<2 or <20 μm) is a major determinant of soil specific surface area (SA). We noted that soil SA coverage with SOM changed dramatically at a specific ratio of either clay (<2 μm) or clay+silt (<20 μm) with soil OC. This is an indirect support of the recently suggested quantification of the soil mineral ‘saturation’ hypothesis. More studies are needed on the causal relationships. We conclude that clay/OC~10 or (clay+silt20μm)/OC~20 are corresponding indices reflecting shift in soil physical behavior

A modification of the mixed form of Richards equation and its application in vertically inhomogeneous soils

Recently, new soil data maps were developed, which include vertical soil properties like soil type. Implementing those into a multilayer Soil-Vegetation-Atmosphere-Transfer (SVAT) scheme, discontinuities in the water content occur at the interface between dissimilar soils. Therefore, care must be taken in solving the Richards equation for calculating vertical soil water fluxes. We solve a modified form of the mixed (soil water and soil matric potential based) Richards equation by subtracting the equilibrium state of soil matrix potential ψE from the hydraulic potential ψh. The sensitivity of the modified equation is tested under idealized conditions. The paper will show that the modified equation can handle with discontinuities in soil water content at the interface of layered soils