Résumé : Earthworms are known to significantly influence soil aggregate stability and hence to regulate underlying ecosystem functions such as soil organic matter (SOM) decomposition and soil erosion. However the, available research information on this aspect in the tropics, and especially in Asia, is...Earthworms are known to significantly influence soil aggregate stability and hence to regulate underlying ecosystem functions such as soil organic matter (SOM) decomposition and soil erosion. However the, available research information on this aspect in the tropics, and especially in Asia, is rather scanty. The aims of this paper are therefore to study the influence of Amynthas khami, an anecic earthworm species, on soil structural properties on one hand, and to determine the factors involved and the consequences for the soil matrix properties on the other hands. Investigations were carried out in different management systems ranging from low to high above-ground casts density. We measured the physical and chemical properties and water behavior (mean weight diameter: MWD, and water drop penetration time: WDPT) of casts and those of the surrounding soil aggregates (control). Pore space was quantified using a morphological approach and 2D image analysis. Soil aggregate stability was primarily specific for each-land use type and afterwards affected by earthworm activity within each ecosystem. Earthworm casts were always more stable than control surrounding soil aggregates. Casts were characterized by higher pH. C, polysaccharides, Ca2+, Mg2+ and K+ contents. Conversely, the particle size fraction and the content of oxides (Al-cbd and Fe-cbd) were not significantly affected by earthworm activity. Soil porosity was sharply decreased in casts as compared to the surrounding soil aggregates and casts were characterized by the absence of packing void poroids and large pores > 50,000 mu m(2). Regressions between soil physico-chemical properties and MWD underlined the relationships between SOM (C and polysaccharide content), pH, Ca2+ content, soil porosity, and the structural stability of cast aggregates. Surprisingly, the abundance of casts on the soil surface was not related to the bulk density of the soil matrix, suggesting that cast aggregates are not integrated into it or that they are integrated with different soil structural characteristics. (c) 2008 Elsevier B.V. All rights reserved.
Résumé : N2O is a potent greenhouse gas and solutions have to be sought to reduce its emission from agriculture. This work evaluates N2O emission from maize-crop (Zea mays) fields submitted to different organic or mineral fertilizers (pig slurry, matured pig manure or ammonium nitrate) in Brittany...N2O is a potent greenhouse gas and solutions have to be sought to reduce its emission from agriculture. This work evaluates N2O emission from maize-crop (Zea mays) fields submitted to different organic or mineral fertilizers (pig slurry, matured pig manure or ammonium nitrate) in Brittany (France). N2O emission was evaluated along a year in two experimental sites receiving 110 or 180 kg N ha(-1) as ammonium nitrate or pig slurry and 180 or 132 kg N ha(-1) as ammonium nitrate or matured pig manure at Champ Noel and Le Rheu experimental plots, respectively. N2O emission was evaluated by interpolation method of periodic fluxes on the field scale and by simulation with NOE algorithm using measured soil characteristics such as N content and gravimetric moisture and other soil biological properties determined in a previous study (potential denitrifying activity, N2O/[N2O + N-2] ratio during denitrification) or drawn from literature. On the whole N2O emissions vary between 0.3 kg N ha(-1) year(-1) in an unfertilized plot and 2-4 kg N ha(-1) year(-1) under ammonium nitrate fertilization. They were higher under N fertilizer application than without N fertilizer but no significant effect of type of N fertilizer was observed on either site. However, N2O losses immediately after fertilizer application were higher under pig slurry and matured pig manure, while measured and predicted fluxes showed that greater N2O losses occurred from summer to winter under ammonium nitrate application. This could be mainly explained by higher mineral N contents at Le Rheu and higher N2O/(N2O + N-2) ratio at both sites. The NOE model predicted higher annual N2O emission and emission factor with ammonium nitrate at Champ Noel only and similar emissions for both treatments at Le Rheu. These results suggest that in this climate and soil context the use of pig slurry or matured pig manure did not have a stimulating impact on N2O emissions in comparison with a plot receiving a mineral fertilization. (c) 2007 Elsevier B.V. All rights reserved.
Résumé : Composting is a widely used biological process for the management of some wastes produced in communities and agricultural activities, which have experienced substantial growth during the last few years. Because this and the knowledge of composting has increased, the number of composting...Composting is a widely used biological process for the management of some wastes produced in communities and agricultural activities, which have experienced substantial growth during the last few years. Because this and the knowledge of composting has increased, the number of composting facilities has increased tremendously, especially in some European countries. Interest has also increased in several countries in other regions of the world.This book attempts to summarize some of the most important work conducted during the last few years under one cover. The contributions to the publication are made by some of the most qualified professionals in the world and present the information in a clear and objective manner. The readers will find the information very useful and will be helpful in the design of new facilities and organic recycling programs. It features up-to-date contributions by some of the most knowledgeable and respected leaders in the field. It presents clear and objective presentations, which are arranged in such a way that it is not necessary to read the entire book. It provides information that is supported by data, tables and references. It covers most the important aspects of the process including a brief historical review. It may be used by teachers as well as practicioners in the field.
Résumé : The relative importance of different binding mechanisms and associated biological binding agents on aggregate stability is still unclear. The aim of this study was to evaluate the role of various aggregate binding agents during the decomposition of cauliflower residues, wheat straw, cattle manure...The relative importance of different binding mechanisms and associated biological binding agents on aggregate stability is still unclear. The aim of this study was to evaluate the role of various aggregate binding agents during the decomposition of cauliflower residues, wheat straw, cattle manure and poultry woody compost. We measured aggregate stability, hot-water extractable polysaccharide, C mineralization, fungal and microbial biomass dynamics in an amended silt loam soil, under controlled conditions. Soil aggregate stability was measured using three methods involving fast wetting, slow wetting and mechanical breakdown. Aggregate stability to slow wetting followed the same dynamics as C mineralization and was well correlated with polysaccharide content for cauliflower residues and wheat straw. This relationship is in agreement with the hypothesis that the rapid microbially induced improvement in aggregate stability that follows fresh organic residue additions at least partly involves labile polysaccharides. The transient increase in the two other types of stability was not directly related to C mineralization dynamics and seemed to be influenced by fungal hyphal length. Fungi would provide resistance to mechanical breakdown and slaking. The dynamic behaviour of biological binding agents was only partly explained by the initial quality of the organic materials, as characterized by Van Soest proximal fractionation.
Résumé : Selenium is an essential nutrient that is potentially toxic: one of its radio-elements is also a component of long-lived radioactive waste for which long-term deep geological storage is envisaged. The chemistry of Se in soils is complex and very sensitive to redox potential and microbial activity...Selenium is an essential nutrient that is potentially toxic: one of its radio-elements is also a component of long-lived radioactive waste for which long-term deep geological storage is envisaged. The chemistry of Se in soils is complex and very sensitive to redox potential and microbial activity which largely determine its oxidation state and chemical form. The dynamics of Se have been extensively studied in soils where it is deficient, and even more so when concentrations are potentially toxic. In contrast, relatively little information is available on the fate of Se in soils at intermediate concentrations (1-5 mg kg(-1)). Some chemical reactions and biological processes that influence Se dynamics may be strongly concentration dependent. We have followed microbial activity by monitoring soil gas composition and Se volatilization and measured changes in Se fractionation using chemical extractions in a column of aggregated soil. A small proportion of soil Se was accumulated in the leaves, stems and fruits of tomato plants. Net Se volatilization losses were small (0.12% in a two-month period). There was a considerable upward movement of freshly added Se, but not of native soil Se. This vertical mobility was greater than that predicted from solute movement driven by evaporation. Selenium was strongly immobilized at the water-saturated, anoxic base of the soil columns. Straw amendment and the growth of a tomato plant did not lead to stronger association with soil organic matter. It was not possible to correlate changes in fractionation of Se between treatments and along a soil profile with the calculated fraction of anoxia, except in the completely anoxic zone. (C) 2007 Elsevier B.V. All rights reserved.
Résumé : One alternative to mineral fertilization is to use organic fertilizers. Our aim was to compare the impacts of 7-year applications of composted pig manure and ammonium nitrate on the structure and activity of the denitrifying community. Mineralization and organization of N, denitrification rates...One alternative to mineral fertilization is to use organic fertilizers. Our aim was to compare the impacts of 7-year applications of composted pig manure and ammonium nitrate on the structure and activity of the denitrifying community. Mineralization and organization of N, denitrification rates and N2O/N-2 ratio were also investigated. Fourteen months after the last application, the potential denitrifying activity (+319%), N mineralization (+110%) and organization (+112%) were higher under pig compost than under ammonium nitrate fertilization. On the other hand, the N2O/(N2O+N-2) ratio was lower (P < 0.05, n=5) under organic fertilization. These effects of organic fertilization were in accordance with its higher total carbon content and microbial biomass. Fingerprints and clone library analyses showed that the structure of the denitrifying community was affected by the fertilization regime. Our results reveal that organic or mineral fertilizer applications could affect both ! structure and activity of the denitrifying community, with a possible influence on in situ N2O fluxes. These effects of the fertilization regime persisted for at least 14 months after the last application.
Localiser cette bibliothèque : - UMR SAS 204584 : UMR Sol Agro et Hydrosystème Spatialisation (UMR SAS) - Cote = PUBL 1258
ColloqueBiochemical composition and kinetics of C and N mineralization of animal wastes : a typological and modelling approach ( 2005 ) Morvan, Thierry ; Nicolardot, Bernard