Pile-Soil Interaction in Unsaturated Soil Conditions

The degree of saturation has been proven to significantly affect geotechnical engineering designs for foundations. The changes in water content will influence the way the soil behaves, including its strength and stiffness parameters. These characteristics were analyzed for a uniform silty sand by developing P-Y curves, which relate lateral loading to lateral deformations. These P-Y curves were input into FB-Multipier, a software developed by the Bridge Software Institute. The software is capable of generating deformations as a result of user-defined loading cases. The results indicated that the middle range of degrees of saturation produced the least amount of deformation. This is in accordance with stiffer response in partially saturated soils due to the presence of inter-particle suction stresses

The mineralization of commercial organic fertilizers at 8°C temperature

In organic production only organic fertilizers and soil conditioners can be used to supply the soil with nitrogen. The mineralization of these products is slow and so there can be problems with the supply of nitrogen, when the demand of the plants is high. The supply of nitrogen from organic products depends on the speed of their mineralization which is primarily influenced by the composition and formulation of their raw material. In apple production in the Alps-region especially during spring problems with nitrogen supply are common. In that period, the weather conditions are sometimes bad, the temperature in the soil is low and mineralization starts slowly - apple trees demand more nitrogen than the soil can deliver. To compensate the demand of the apple tree organic growers can not use mineral fertilizers but only organic fertilizers and soil conditioners whose mineralization rate is often unknown. There is a strong need in organic fruit production to receive more information about the behaviour of fertilizers in the soil especially concerning their N-release under different conditions. To acquire that information, incubation experiments under controlled conditions (temperature, type of soil, humidity of the soil) were carried out in the laboratory to determine the mineralization-rate of different organic fertilizers and soil conditioners which are available in our region

Role of crop residue mulches and their decomposition on soil functions in conservation agriculture : S11.03a -6

Core principle of Conservation Agriculture is to maintain soil cover by crop residue mulching or cover crops. Mulching practice affects many agroecosystem services, through water dynamics and C and N transformations (Coppens et al., 2007) and their impact on climate change, water and nutrient cycling and soil biological activity. The objectives of this work were (i) to quantify the effects of biotic (diversity of mulches and soil types) and abiotic (climatic conditions) factors on soil functions such as C stabilization, C and N mineralization and transport, GHG emission, microbial dynamics and diversity; (ii) to assess by modeling how these factors affect agroecosystem services in a range of agricultural conditions met in conservation agriculture of France, Brazil and Madagascar. An experiment was performed in controlled conditions with soil columns. The treatments varied either by the type of residue mulch (Zea mais + Doliquos lablab or Triticum aestivum + Medicago sativa), or by the type of soil (sandy or loamy soil ) and by the water regime (manipulated through the intensity and frequency of rain applied to the soil columns). The Pastis_Mulch model (Findeling et al., 2007) tested on the measured data, was then used to simulate different scenarii, particularly different crop rotations and associations representative of the CA agrosystems (amount and quality of crop mulches), amount and distribution of rainfall (dry and wet years) and types of soil. The results allowed to rank the factors according to their positive and negative effects on the different ecosystem services involved. (Texte intégral

Genotype and environment interaction on yield and quality parameters of organically grown winter wheat – Triticum aestivum L. genotypes

The interaction of genotype and environment upon yield and quality parameters of eight winter wheat (Triticum aestivum L.) genotypes was studied under organic conditions in Austria over two growing periods, 2001/2002 and 2002/2003, respectively. Two sites that have significantly different climatic conditions, Innviertel and Marchfeld, were chosen for the field experiment. Study site weather and soil conditions are important yield-affecting factors. Although the yield of Marchfeld-grown genotypes were lower, they had shown higher quality parameter values. Soil moisture conditions increase the grain yield but decrease its quality. To obtain seed with higher quality, a production site with favourable climate conditions should be chosen

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

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

Importance of Soil Quality in Environment Protection

Soil quality can be characterised by the harmony between it’s physical and biological state and the fertility. From the practical crop production viewpoint, some important contrasting factors of soil quality are: (1) soil looseness – compaction; (2) aggregation – clod and dust formation; friable structure – smeared or cracked structure; (3) organic material: conservation – decrease; (4) soil moisture: conservation – loss; water transmission – water-logging; (5) at least soil condition as a result of the long term ef ect of land use moderates or strengthens climatic harm. In our long-term research project practical soil quality factors were examined in arable i eld and experimental conditions. We state that prevention of the soil quality deterioration can be done by the developing and maintaining harmony between land use and environment. Elements of the soil quality conditions such as looseness, aggregation, workability, organic matter, water transport are examined and the improving methods are suggested. Tillage and production factors which can be adopted to alleviate the harmful climatic impacts are also summarised

A biomarker based on gene expression indicates plant water status in controlled and natural environments

Plant or soil water status are required in many scientific fields to understand plant responses to drought. Because the transcriptomic response to abiotic conditions, such as water deficit, reflects plant water status, genomic tools could be used to develop a new type of molecular biomarker. Using the sunflower (Helianthus annuus L.) as a model species to study the transcriptomic response to water deficit both in greenhouse and field conditions, we specifically identified three genes that showed an expression pattern highly correlated to plant water status as estimated by the pre-dawn leaf water potential, fraction of transpirable soil water, soil water content or fraction of total soil water in controlled conditions. We developed a generalized linear model to estimate these classical water status indicators from the expression levels of the three selected genes under controlled conditions. This estimation was independent of the four tested genotypes and the stage (pre- or post-flowering) of the plant. We further validated this gene expression biomarker under field conditions for four genotypes in three different trials, over a large range of water status, and we were able to correct their expression values for a large diurnal sampling period.Comment: Plant, Cell & Environment, 201

Impact of soil tillage and land use on soil organic carbon decline under Mediterranean conditions

Soils under Mediterranean climate conditions frequently have low to very low levels of soil organic matter (SOM), as a result of low biomass production under the predominantly rainfed conditions and the intensive tillage operations commonly practiced. In order to assess both short and long-term impacts of soil tillage and land use on soil organic carbon, two sets of experiments were performed. One consisted in the identification and soil analysis of 3 pairs of sites under different soil types and land use over 5 to 30 years; in the second experiment a long-term fallow area was repeatedly submitted to different types of soil tillage management (mouldboard plough + disc harrow; non-inversion tine cultivation; no-till) over 3 years. Soil texture, bulk density and SOM were analysed along the whole soil profile in the first experiment, whereas bulk density and SOM to a depth of 30 cm was measured before the first tillage operations and at the end of the observation period in the second experiment. The results clearly indicate that tillage based land use, irrespective of the type of land use, caused a considerable decline in SOM content in the tilled soil layer. Very small and inconsistent differences in SOM between paired soil profiles were observed in the lower part of the profiles. In the second experiment with three types of tillage systems, SOM content decreased with tillage intensity. Avoidance of soil disturbance is an important step towards halting SOM decline under Mediterranean climate conditions