共查询到20条相似文献，搜索用时 15 毫秒
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A. Castrignan G. Buttafuoco A. Canu C. Zucca S. Madrau 《Land Degradation \u0026amp; Development》2008,19(2):198-213
Soil erosion varies greatly over space and is commonly estimated using the revised universal soil loss equation (RUSLE). Neglecting information about estimation uncertainty, however, may lead to improper decision‐making. One geostatistical approach to spatial analysis is joint stochastic simulation, which draws alternative, equally probable, joint realizations of a regionalized variable. Differences between the realizations provide a measure of spatial uncertainty and allow us to carry out an error propagation analysis. The objective of this paper was to assess spatial uncertainty of a soil erodibility factor (K) model resulting from the uncertainties in the input parameters (texture and organic matter). The 500 km2 study area was located in central‐eastern Sardinia (Italy) and 152 samples were collected. A Monte Carlo analysis was performed where spatial cross‐correlation information through joint turning bands simulation was incorporated. A linear coregionalization model was fitted to all direct and cross‐variograms of the input variables, which included three different structures: a nugget effect, a spherical structure with a shorter range (3500 m) and a spherical structure with a longer range (10 000 m). The K factor was then estimated for each set of the 500 joint realizations of the input variables, and the ensemble of the model outputs was used to infer the soil erodibility probability distribution function. This approach permitted delineation of the areas characterized by greater uncertainty, to improve supplementary sampling strategies and K value predictions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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The hardsetting surface of many Alfisols in Australia is a limiting factor in crop production. Better soil management systems are required to improve productivity. This study reports the effects of several untested management systems, involving the combined effects of tillage (deep ripping, deep mouldboard ploughing and disc ploughing), irrigation layout (permanent beds, border ditch) and crop rotation treatments (single cropping, double cropping and pasture), on soil structure and the production of irrigated soybeans [Glycine max (L) Merr.] on a hardsetting Alfisol. It was conducted under a system of controlled traffic near Trangie, NSW, Australia. The double cropping and pasture treatments increased total water entry, soil organic carbon and soybean leaf water potential. Consequently, soybean yield was increased by as much as 58%. The retention of cereal and pasture stubble increased total water entry by slowing the rate of irrigation water advance, reducing the potential for slaking and increasing the number of continuous vertical macropores. The increases in soil water were associated with a reduction in soil strength; a key limiting factor in crop growth on hardsetting Alfisols. Deep tillage or the use of permanent beds did not affect soybean yields under the conditions reported in this paper, although the combination of disc ploughing and furrow irrigation was successful. 相似文献
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Flemming Ekelund Stephane Saj Mette Vestergrd Joanne Bertaux Juha Mikola 《Soil biology & biochemistry》2009,41(11):2336-2342
Protozoa stimulate plant growth, but we do not completely understand the underlying mechanisms, and different hypotheses seek to explain this phenomenon. To test these hypotheses, we grew the grass Yorkshire fog (Holcus lanatus) in pots with soil, which contained either (1) no organisms but bacteria – or (2) bacteria and protozoa. Half of the pots received a glucose treatment so as to mimic an additional root exudation. We measured plant growth and plant nitrogen uptake, along with various microbial pools and processes that support plant growth. Protozoan presence significantly enhanced soil nitrogen mineralization, plant nitrogen uptake from organic nitrogen sources, plant nitrogen content, and plant growth. By contrast, we found no evidence that glucose addition, mimicking root exudation, increased soil nitrogen availability and plant nitrogen uptake. Moreover, although protozoan presence affected bacterial community structure, it did not affect the proportion of IAA-producing bacteria in the community or plant root morphology. These results refute the “soil microbial loop” hypotheses, which suggest that protozoan stimulation of plant growth results from complex interactions between plant roots, bacteria and protozoa. Our experiment thus favours the simple explanation that increased nitrogen availability is the key factor behind the positive protozoan effect on plant growth. To exploit natural resources in an efficient and environmentally friendly way, we need to understand in detail the functioning of ecosystems. This study stresses that to achieve this, it is still urgent, besides investigating intricate food-web and signal compound interactions, also to focus on the basic stoichiometric and energetic aspects of organisms. 相似文献
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The main conclusions of the Malian-Dutch “Primary Production in the Sahel (PPS)” research project, which was carried out during 1976–1981 (Penning de Vries and Djitèye, 1982), may be summarized as follows: (1) poor soil quality is just as great a barrier to rural development as water shortage; (2) animal production is high per unit area, compared with similar ecological zones in the U.S.A. and Australia; (3) attempts to increase production without due attention to the shortage of soil nutrients are bound to fail; (4) socio-economic conditions determine the feasibility of productive investments in agriculture in the Sahel. This article presents the PPS approach to publicizing these results and promoting a badly needed revision of development policy in the Sahel. 相似文献
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Accumulation soils like those known as “Ockererde” are not yet represented in the German and in international soil‐classification systems, even though they represent important members of catenas found in humid low‐mountain areas influenced by the translocation of interpedon matter. Currently, this soil is referred to as “(Hang‐)Oxigley”, though this does not take into account its water and matter dynamics. Six representative catenas in the Black Forest (SW Germany) will be used to describe the occurrence, extent, and properties of the accumulation‐affected “Ockererde” derived from a variety of parent materials at specific altitudes. On the basis of their morphological, chemical, and physical properties as well as matter dynamics, it is possible to distinguish “Ockererde” clearly from soil units with similar characteristics (“Lockerbraunerde”, Andosols). Finally, suggestions will be given for the classification of “Ockererde”. 相似文献
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Micromorphological characteristics indicate that in southwestern Wisconsin pedogenesis transgressed the Sangamonian-Wisconsinan chronostratigraphic boundary in conjunction with colluvial and eolian sedimentation. The use of micromorphology helps to distinguish between pedological, colluvial, and eolian components in the paleosol horizon sequence, which can be difficult to resolve and interpret solely from field investigations and from other laboratory analyses. Results show that a basal loess “mixed zone” within the welded paleosol profile contains features that are the products of colluvial reworking processes. We present micromorphology data which support stratigraphic relationships suggesting that colluvial processes were important in the formation of basal loess “mixed zones” in addition to other possible mixing processes such as pedoturbation and bioturbation. 相似文献
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Craig F. Morris James A. Anderson G. E. King Arthur D. Bettge Kimberly Garland‐Campbell R. E. Allan E. Patrick Fuerst Brian S. Beecher 《Cereal Chemistry》2011,88(6):576-583
Kernel texture in wheat (Triticum sp.) is central to end‐use quality and utilization. Here we report the discovery of a novel soft kernel trait in soft white winter wheat (T. aestivum L.). Two heritable kernel phenotypes were selected among F3‐derived sibs, hereafter designated “normal soft” (wild‐type) and “super soft.” Normal soft lines exhibited single kernel characterization system (SKCS) hardness index (HI) values typical of soft wheat (HI ≈ 20), whereas the super soft lines were unusually soft (HI ≈ 5). Under some environments, individual super soft lines exhibited HI values as low as HI = –4. The super soft trait was manifested in reduced SKCS kernel texture and higher break flour yields, with some increase in sodium carbonate SRC (solvent retention capacity) values and sponge cake volumes. Straight‐grade flour yield, flour ash, milling score, and cookie diameter were largely unaffected. With the possible exception of the sodium carbonate SRC values, we observed no indication that the super soft trait conferred any negative aspects to commercial soft wheat quality. As such, the super soft trait may provide wheat breeders with new opportunities to modify the end‐use quality of wheat. 相似文献
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《植物养料与土壤学杂志》2017,180(2):165-168
Glucose is widely used to study the dynamics of easily available organics in soil. Pure culture studies have revealed that many microorganisms can sense and respond to glucose through chemosensory mechanisms that are not directly reliant on energy catabolism. However, the rapid mineralization of glucose by microorganisms makes it difficult to disentangle its energy effects from such non‐catabolic interactions. “Non‐metabolizable” glucose analogues have proven useful in mechanistic studies of glucose in pure culture, but have never been applied to complex microbial communities in soil. We sought to determine how their mineralization in soil differs from that of glucose, and whether they have potential as a new approach for investigating chemosensory mechanisms in soil microbiology. We incubated soil from an agricultural Haplic Luvisol under controlled conditions for 24 d and monitored CO2 efflux after addition of (1) glucose, and three “non‐metabolizable” glucose analogues: (2) 2‐deoxyglucose (DG), (3) α‐methylglucoside (αMG), and (4) 3‐O‐methyl‐glucose (OMG), at three concentration levels, along with a control. All three analogues did in fact produce a large increase in soil CO2 efflux, but the dynamics of their mineralization differed from the rapid degradation seen for glucose. At medium and high concentrations, CO2 efflux peaked between 2.5 and 4 d after amendment with DG and αMG, and was delayed by about one week for OMG. The markedly different patterns of mineralization between glucose and OMG offer a new tool for investigating the behavior of glucose in soil. By using OMG as a glucose model, chemosensory mechanisms could be studied with limited interference from energy catabolism. 相似文献
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This assessment examines the extent to which advisory services are able to address current and emerging knowledge needs of practitioners (primarily farmers) about sustainable soil management (SSM) in Europe. The assessment is structured around the following components: the context of advice (policy, market, socio‐economic conditions, privatization of advisory systems); the challenges that SSM presents for advice; the current and emerging practitioner knowledge needs; and the existing structure and function of advisory services for SSM. The analysis reveals fragmented policy and advisory services, paralleled by the multi‐scale character of SSM and a diverse audience for advice. The challenges and opportunities this complex arena presents are analysed, and suggestions made for achieving more effective advisory services for SSM, together with examples of existing approaches. 相似文献
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A. E. Nychas 《植物养料与土壤学杂志》1984,147(5):584-591
The constant parameters k1, k2 (in ml/μg P) and b1, b2 (in μg P/g soil) of the two-surface Langmuir Equation for phosphate adsorption were determined by three methods for ten high pH montmorillonitic soils. The techniques included a graphical approach in which a curve is resolved into two straight line components (“Hofstee” method) and two methods utilizing the regression characteristics of the experimental adsorption data. The first regression method obtains estimates of k1, k2, b1 and b2 indirectly through various relationships resulting from the mathematical representation of the sorption isotherm as a “Stieltjes” transform (“Sposito” method). The second regression method obtains the parameters directly, assuming that k1 ? k2 and b1 ? b2 (“Approximation” method). Statistical analyses showed that each method yielded significantly different k1 and k2 constants compared to the other two. With regard to b1 and b2, the “Approximation” method produced significantly higher b1 and lower b2 values in all samples, though no difference was found among the three methods for the theoretical adsorption maximum (bT=b1+b2). The relationship between k1 and k2 as well as b1 and b2, as expressed by their ratios, changed significantly from one method to another. This indicates the need for a more precise arithmetic definition of the condition k1 ? k2 and b1 ? b2 which is necessary for the “Approximation” method, accepted so far to be valid for k1 ～ 100 k2 and b1 ～ 0,3 b2 respectively. 相似文献
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《Cereal Chemistry》2017,94(3):377-379
Several oat processors in the United States and Canada operate under what is referred to as a Purity Protocol for the provision of gluten‐free oats. This term is derived from a Health Canada position statement that indicated that pure oats, which they defined as oats that are harvested, transported, stored, processed, and manufactured under good manufacturing practices (GMPs) to minimize the presence of gluten, can safely be consumed by some persons with celiac disease. While proprietary definitions of the appropriate GMPs have been used in industry for many years, no independent definition of the requirements to make a Purity Protocol claim has been published. This paper provides a consensus definition of the Purity Protocol requirements based on input from the four largest Purity Protocol oat processors in North America. This definition provides transparency to gluten‐free consumers and allows for auditing of a Purity Protocol claim. 相似文献
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Relationships between “available” soil phosphorus and foliar phosphorus content of Tectona grandis (teak) in West-Africa Significant relationships were analysed between the foliar phosphorus content of Tectona grandis L. and the topsoil phosphorus contents on a broad range of soils in West African plantations of Tectona grandis L. (teak), except for soils very poor in clay or organic matter (< 15% T or < 1% C). Of all methods used (P-H2O, P-Mehlich, P-CAL, P-Bray-1, P-Soltanpour, P-Dabin, P-Resin, P-H2SO4, P-550, P-org) the fraction of soil P (P-550) dissolved in 1 n H2SO4 after dry ashing at 550 °C (r = 0.548***, n = 63) and the method of Bray-1 (r = 0.505***, n = 63) show the best results. The first reflects 80-90% of the organic P content and is recommended for the evaluation of the phosphorus supply. Using multiple correlation analysis we found a highly significant relationship (R = 0.794***, R2 = 0.63, n = 58) between foliar P as depending variable and P-Bray (positive), the soil sand content (negative) as well as soil pH (positive). A sufficient phosphorus supply of teak foliage (0.2% P) occured at soil levels of 300-320 kg P per ha and 15 cm (or more than 150 mg P/kg in topsoils free of stones (P-550)) in the studied area between Benin and Liberia. 相似文献