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"Soil Science"
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How do animals help make soil?
An introduction to the ways in which \"some animals break down dead plants to creat new soil, while others spread nutrients around\"--Page 4 of cover.
Book
Redox potential (Eh) and pH as drivers of soil/plant/microorganism systems: a transdisciplinary overview pointing to integrative opportunities for agronomy
Background Oxidation-reduction and acid-base reactions are essential for the maintenance of all living organisms. However, redox potential (Eh) has received little attention in agronomy, unlike pH, which is regarded as a master variable. Agronomists are probably depriving themselves of a key factor in crop and soil science which could be a useful integrative tool. Scope This paper reviews the existing literature on Eh in various disciplines connected to agronomy, whether associated or not with pH, and then integrates this knowledge within a composite framework. Conclusions This transdisciplinary review offers evidence that Eh and pH are respectively and jointly major drivers of soil/plant/microorganism systems. Information on the roles of Eh and pH in plant and microorganism physiology and in soil genesis converges to form an operational framework for further studies of soil/plant/microorganism functioning. This framework is based on the hypothesis that plants physiologically function within a specific internal Eh-pH range and that, along with microorganisms, they alter Eh and pH in the rhizosphere to ensure homeostasis at the cell level. This new perspective could help in bridging several disciplines related to agronomy, and across micro and macro-scales. It should help to improve cropping systems design and management, in conventional, organic, and conservation agriculture.
Journal Article
Celebrating soil : discovering soils and landscapes
\"This richly illustrated book celebrates the diversity, importance, and intrinsic beauty of soils around the world and helps the reader to understand the ways that soils are related to the landscapes in which they form. The book unravels the complex bond between humans and soils and the importance of soils in our cultures and everyday lives. Soil is critical to terrestrial life on earth. It underpins human food supply and provides materials on which we build our lives. Soil is out of sight and often out of mind, thus easy to overlook. Yet soil has tremendous variety and intrinsic beauty for those who care to look. Soil contains a memory of the events that have shaped the landscape and the environment. With help you can look at a soil and understand the stories that it has to tell. Written in a reader-friendly way, Celebrating Soil is a wonderful resource for farmers, horticulturalists, naturalists, students and others who are concerned about how soils are formed, work and are used.\"--Provided by publisher.
Book
Multiple factors influence the role of arbuscular mycorrhizal fungi in soil aggregation—a meta-analysis
Background and aims Soil aggregation is a crucial aspect of ecosystem functioning in terrestrial ecosystems. Arbuscular mycorrhizal fungi (AMF) play a key role in soil aggregate formation and stabilization. Here we quantitatively analyzed the importance of experimental settings as well as biotic and abiotic factors for the effectiveness of AMF to stabilize soil macroaggregates. Methods We gathered 35 studies on AMF and soil aggregation and tested 13 predictor variables for their relevance with a boosted regression tree analysis and performed a meta-analysis, fitting individual random effects models for each variable. Results and conclusions The overall mean effect of inoculation with AMF on soil aggregation was positive and predictor variable means were all in the range of beneficial effects. Pot studies and studies with sterilized sandy soil, near neutral soil pH, a pot size smaller than 2.5 kg and a duration between 2.2 and 5 months were more likely to result in stronger effects of AMF on soil aggregation than experiments in the field, with non-sterilized or fine textured soil or an acidic pH. This is the first study to quantitatively show that the effect of AMF inoculation on soil aggregation is positive and context dependent. Our findings can help to improve the use of this important ecosystem process, e.g. for inoculum application in restoration sites.
Journal Article
Deep soil organic matter—a key but poorly understood component of terrestrial C cycle
Despite their low carbon (C) content, most subsoil horizons contribute to more than half of the total soil C stocks, and therefore need to be considered in the global C cycle. Until recently, the properties and dynamics of C in deep soils was largely ignored. The aim of this review is to synthesize literature concerning the sources, composition, mechanisms of stabilisation and destabilization of soil organic matter (SOM) stored in subsoil horizons. Organic C input into subsoils occurs in dissolved form (DOC) following preferential flow pathways, as aboveground or root litter and exudates along root channels and/or through bioturbation. The relative importance of these inputs for subsoil C distribution and dynamics still needs to be evaluated. Generally, C in deep soil horizons is characterized by high mean residence times of up to several thousand years. With few exceptions, the carbon-to-nitrogen (C/N) ratio is decreasing with soil depth, while the stable C and N isotope ratios of SOM are increasing, indicating that organic matter (OM) in deep soil horizons is highly processed. Several studies suggest that SOM in subsoils is enriched in microbial-derived C compounds and depleted in energy-rich plant material compared to topsoil SOM. However, the chemical composition of SOM in subsoils is soil-type specific and greatly influenced by pedological processes. Interaction with the mineral phase, in particular amorphous iron (Fe) and aluminum (Al) oxides was reported to be the main stabilization mechanism in acid and near neutral soils. In addition, occlusion within soil aggregates has been identified to account for a great proportion of SOM preserved in subsoils. Laboratory studies have shown that the decomposition of subsoil C with high residence times could be stimulated by addition of labile C. Other mechanisms leading to destabilisation of SOM in subsoils include disruption of the physical structure and nutrient supply to soil microorganisms. One of the most important factors leading to protection of SOM in subsoils may be the spatial separation of SOM, microorganisms and extracellular enzyme activity possibly related to the heterogeneity of C input. As a result of the different processes, stabilized SOM in subsoils is horizontally stratified. In order to better understand deep SOM dynamics and to include them into soil C models, quantitative information about C fluxes resulting from C input, stabilization and destabilization processes at the field scale are necessary.
Journal Article
Dirt : the erosion of civilizations
An engaging natural and cultural history of soil that sweeps from ancient civilisations to modern times, 'Dirt' explores the compelling idea that we are - and have long been - using up Earth's soil.
Book
Does biochar influence soil physical properties and soil water availability?
AIMS: This study aims to (i) determine the effects of incorporating 47 Mg ha⁻¹ acacia green waste biochar on soil physical properties and water relations, and (ii) to explore the different mechanisms by which biochar influences soil porosity. METHODS: The pore size distribution of the biochar was determined by scanning electron microscope and mercury porosimetry. Soil physical properties and water relations were determined by in situ tension infiltrometers, desorption and evaporative flux on intact cores, pressure chamber analysis at −1,500 kPa, and wet aggregate sieving. RESULTS: Thirty months after incorporation, biochar application had no significant effect on soil moisture content, drainable porosity between –1.0 and −10 kPa, field capacity, plant available water capacity, the van Genuchten soil water retention parameters, aggregate stability, nor the permanent wilting point. However, the biochar-amended soil had significantly higher near-saturated hydraulic conductivity, soil water content at −0.1 kPa, and significantly lower bulk density than the unamended control. Differences were attributed to the formation of large macropores (>1,200 μm) resulting from greater earthworm burrowing in the biochar-amended soil. CONCLUSION: We found no evidence to suggest application of biochar influenced soil porosity by either direct pore contribution, creation of accommodation pores, or improved aggregate stability.
Journal Article
Decreased soil microbial biomass and nitrogen mineralisation with Eucalyptus biochar addition to a coarse textured soil
Background and Aims Biochar has been shown to aid soil fertility and crop production in some circumstances. We investigated effects of the addition of Jarrah (Eucalyptus marginata) biochar to a coarse textured soil on soil carbon and nitrogen dynamics. Methods Wheat was grown for 10 weeks, in soil treated with biochar (0, 5, or 25 t ha−1) in full factorial combination with nitrogen (N) treatments (organic N, inorganic N, or control). Samples were analysed for plant biomass, soil microbial biomass carbon (MBC) and nitrogen (MBN), N mineralisation, CO2 evolution, community level physiological profiles (CLPP) and ammonia oxidising bacterial community structure. Results MBC significantly decreased with biochar addition while MBN was unaltered. Net N mineralisation was highest in control soil and significantly decreased with increasing addition of biochar. These findings could not be attributed to sorption of inorganic N to biochar. CO2 evolution decreased with 5 t ha−1 biochar but not 25 t ha−1. Biochar addition at 25 t ha−1 changed the CLPP, while the ammonia oxidising bacterial community structure changed only when biochar was added with a N source. Conclusion We conclude that the activity of the microbial community decreased in the presence of biochar, through decreased soil organic matter decomposition and N mineralisation which may have been caused by the decreased MBC.
Journal Article