Search

Soil aggregate stability is a crucial property regarding soil erodibility. However, results from different stability-assessment methods differ. The objective of this study was to compare two such m...

Aggregate stability, one of the main factors controlling soil erodibility, varies over time. Knowledge of its variation would help to identify better soil management practices. In 10 soils from central Greece devoted to cereal cropping, seasonal wet aggregate stability (WAS) fluctuations were investigated over a period of two successive years. The wet-sieving technique of air-dried aggregates was used for WAS determinations, according to a test resulting in an instability index calculation. Over the first year, when typical Mediterranean climatic conditions dominated, WAS varied according to a nearly cyclic pattern, from a low in winter or early-spring months to a high in summer months. The instability index varied from a high between 123–152% of annual average to a low between 58–83% of annual average. Total monthly rainfall (TR) and mean monthly air temperature (MAT) strongly correlated with seasonal WAS. Their ratio (TR/MAT, ombrothermic ratio) has been proved to be a good predictor of structural stability throughout the year, for most of the soils studied. Possible mechanisms deteriorating aggregation seemed to be raindrop impact, repeated soil drying and wetting and repeated soil freezing and thawing, while possible mechanisms promoting aggregation seemed to be soil drying and warming and biological activity. Over the second year, severe climatic inconsistencies complicated the seasonal pattern of WAS response. From January to March, WAS unexpectedly increased, obtaining its maximum value for most of the soils in March, then it varied inconsistently until October and thereafter decreased, obtaining its minimum value in December for all soils. The instability index varied from a high between 130–196% of annual average to a low between 61–83% of annual average. Uneven seasonal distribution of climatic characteristics and extreme events decisively modified the typical for Mediterranean conditions seasonal WAS variation pattern. Copyright © 2009 John Wiley & Sons, Ltd.

Soil structure may be improved by adding readily decomposable organic matter. The extent of amelioration depends on the chemical build-up and decomposability of the crop residues. Three different kinds of organic matters were investigated: (1) maize stem, (2) wheat straw, and (3) maize stem& wheat straw. Comparing the aggregate stabilizing effects of the differently decomposable organic matters to each other, the expected maize stem & wheat straw (mw) > maize stem (m) > wheat straw (w) order was proved.

During raindrop impact soil, aggregates breakdown and produce finer, more transportable particles and micro-aggregates. These particles and micro-aggregates appreciably affect the processes of infiltration, seal and crust development, runoff, and soil erosion. Aggregate stability is, therefore, an important property that may explain, quantify, and predict these processes. This study was designed to develop improved formulae for assessing interrill erosion rate by incorporating the aggregate stability index ( A s ) in the prediction evaluations for soil erodibilites of Ultisols in subtropical China. Field experiments of simulated rainfall involving rainstorm simulations with medium and high rainfall intensity were conducted on six cultivated soils for which the soil aggregate stability was determined by the LB-method. This study yielded two prediction equations D i = 0.23 A s I 2 (1.05 − 0.85 exp −4sin θ ) and D i = 0.34 A s qI (1.05 − 0.85 exp −4sin θ ) that allowed a comparison of their efficiency in assessing the interrill erosion rate. A s is an aggregate stability index, which reflected the main mechanisms of aggregate breakdown in interrill erosion process, θ is the slope angle, I is the rainfall intensity, and q is the runoff rate. Relatively good agreement was obtained between predicted and measured values of erosion rates for each of the prediction models ( R 2 = 0.86 ** , and R 2 = 0.90 ** ). It was concluded that these formulae based on the stability index, A s , have the potential to improve methodology for assessing interrill erosion rates for the subtropical Chinese Ultisols. Considering the time-consuming and costly experimentation of runoff rate measurements, the equation without runoff rate ( q ) was the more convenient and effective one to predict interrill erosion rates on Ultisols of subtropical China.

Avaliaram-se, neste trabalho, em experimento de campo, os efeitos da aplicação, durante dois anos consecutivos, de doses crescentes de um biossólido industrial (0, 6, 12, 18 e 24 Mg ha-1 base seca) e da adubação mineral no cultivo de milho sobre atributos químicos e físicos de um Cambissolo distrófico sob Brachiaria sp. A análise química mostrou que a aplicação do biossólido melhorou a fertilidade do solo, especialmente em doses superiores a 12 Mg ha-1, apresentando maiores teores de C orgânico, nutrientes, Na, CTC, soma de bases, porcentagem de saturação por bases e menor pH que o solo sem adubação, com adubação mineral e de área adjacente, até a profundidade de 0,6 m. Os teores de Cd e Pb não alteraram significativamente enquanto os de N-NO3- e Na aumentaram com as doses e em profundidade atingindo, respectivamente, 53 e 47 mg dm-3, na camada de 0,4-0,6 m com 24 Mg ha-1 de biossólido. A aplicação do biossólido aumentou a estabilidade de agregados, a porosidade total e a microporosidade e reduziu a densidade do solo. O biossólido melhorou a fertilidade e a estrutura do solo, porém sua utilização como insumo agrícola deve ser controlada, respeitando critérios e normas vigentes para que seus benefícios superem os riscos de poluição ambiental.The effects of applying increasing doses of an industrial biosolid (0, 6, 12, 18 and 24 Mg ha-1 dry matter) and mineral fertilizer for two consecutive years in corn cultivation on the chemical and physical attributes of a distrophic Inceptisol under Brachiaria sp. have been evaluated in a field experiment. The chemical analysis showed that the biosolid application improved the soil fertility, especially in doses higher than 12 Mg ha-1, presenting higher organic carbon, nutrients and sodium contents, CEC, sum of bases and saturation percentage for bases and smaller pH than the control soil, with mineral fertilizer and of adjacent area, up to a depth of 0.6 m. The Cd and Pb contents were not altered significantly, while the nitrate and sodium contents increased with doses and depth, reaching 53 and 47 mg dm-3, respectively, in the 0.4-0.6 m depth layer with 24 Mg ha-1 of biosolid. The biosolid application enhanced soil aggregate stability, total porosity and microporosity and reduced soil density. The biosolid improved the fertility and the structure of soil, but its use as an agricultural input must be controlled, respecting criteria and standards so that the benefits of agricultural application overcome the risks of environmental pollution.

This study had the objective of characterizing the main soil types cultivated with melon, based on physical features, in the Apodi Tableland, state of Rio Grande do Norte, to provide basic information for an adequate soil and crop management. Three soil types were studied, in September 2003: Cambissolo Haplico Ta eutrofico tipico - CXve (Typic Haplocambids), Latossolo Vermelho-Amarelo eutrofico tipico - LVAe (Typic Eutrotorrox) e Argissolo Vermelho distrofico arenico - PVd (Arenic Kandiustults). A general analysis of the soil physical attributes in the profiles revealed bulk density values above the normal values for such soils, while higher values were found for the profiles 2 (LVAe) and 3 (PVd), expressed in the total porosity and the imbalance of the ratio of macro:microporosity. The irrigation management of the three soils must be differentiated, according to the ratio of macro: microporosity. The soil aggregate stability in water was satisfactory in all profiles studied; the capacity of available water at a depth of 30 cm (real depth for musk melon roots) decreased from profile 1 (CXve) to profile 3 (PVd). The soil use and management decreased the flocculation degree of the surface horizons of the profiles 1 (CXve) and 2 (LVAe) and, considering the plasticity index, the degradation risk for the use of machines and implements is accentuated in profile 1 (CXve) and low in the profiles 2 (LVAe) and 3 (PVd).

Organic waste amendments have the potential to influence the amount and chemical composition of surface aggregates within a soil. Organic waste amendment-induced changes in soil aggregate stability and chemical concentrations have potential to not only directly affect localized flora and fauna, but can also indirectly affect human health by impacting the transport of nutrients to surface and groundwater. Soil samples were collected from long-term research experiments located at the Oklahoma Panhandle Research and Extension Center receiving annual, spring applications of 0, 168 and 504 kg N ha−1 of beef manure, swine effluent, or anhydrous ammonia applications under conventionally-tilled, continuous corn (Zea mays L.). Aggregates one to two mm in diameter were collected and separated into stable and non-stable fractions and both fractions were analyzed for total phosphorus, potassium, copper, zinc and boron concentrations using ICAP-AES. Results showed swine effluent and anhydrous ammonia applications significantly decreased aggregate stability as compared to the control. In addition, potassium and boron were found in higher concentrations in the non-stable aggregates verses stable aggregates within the control and plots receiving 168 kg N ha−1 beef manure and 168 kg N ha−1 anhydrous ammonia.

Summary Most research on glomalin-related soil proteins (GRSP) has focused on the role of arbuscular mycorrhizal fungi in soil aggregation and environmental engineering. Recently, with the description of the glomalin gene sequence and other results, work on this protein has shifted to include fungal physiology. Based on recent findings, we develop a new model for the role of glomalin; we postulate a primary role in fungal physiology and secondarily arising effects in the soil environment that lead to observed correlations of GRSP with soil aggregate stability. Concurrent with advances in molecular biology, several recent studies have highlighted problems with quantifying GRSP from soil. We summarize and discuss limitations of the methods currently used for GRSP extraction and quantification in soils. We finish with a set of recommendations for research directions that involve testing the model proposed here.

Andisol soil has very good soil physical characteristic, however it has problem with the P retention. Giving ameliorant to reduce the P retention is expected to maintain, moreover to improve some soil physical characteristics. The objective of this research was to find out the interaction between steel slag and bokashi of husk to bulk density, aggregate stability, soil porosity and biomass of broccoli on Andisol Lembang. This study used a randomized block design factorial with two factors. The first factor was steel slag and the second factor was bokashi of husk. Each of them consisted of 4 levels: 0%, 2.5%, 5.0% and 7.5% with two replications. The result of this research showed there was not interaction between steel slag and bokashi of husk to soil bulk density, soil aggregate stability, soil porosity and biomass of broccoli. The statistical results showed that bokashi of husk influence independently to decreasing soil bulk density until 0.53 g cm-3, decreasing soil aggregate stability until 3.25 and increasing soil porosity until 80.22%, but the provision of steel slag and bokashi of husk didn‟t influence to biomass of broccoli. Keywords : organik matter, silicate, bulk density, agreggate stability, broccoli ABSTRAK Andisol mempunyai sifat fisika tanah yang baik, namun bermasalah dengan retensi P. Pemberian amelioran untuk mengurangi retensi P, diharapkan dapat mempertahankan, bahkan meningkatkan beberapa parameter fisika tanah tersebut. Penelitian bertujuan untuk mengetahui interaksi terak baja dengan bokashi sekam padi terhadap bobot isi, kemantapan agregat, porositas tanah dan biomassa tanaman brokoli pada Andisol Lembang. Penelitian menggunakan Rancangan Acak Kelompok Pola Faktorial dengan dua faktor. Faktor pertama terak baja dan faktor kedua bokashi sekam padi masing-masing 4 taraf: 0%, 2,5%, 5,0% dan 7,5%, diulang dua kali. Hasil penelitian menunjukkan bahwa tidak terjadi interaksi antara terak baja dengan bokashi sekam padi terhadap bobot isi, kemantapan agregat, porositas tanah dan biomassa tanaman brokoli. Hasil statistik menunjukkan bahwa bokashi sekam padi berpengaruh mandiri untuk menurunkan bobot isi tanah sampai 0.53 g cm-3, menurunkan kemantapan agregat tanah sampai 3,25 dan meningkatkan porositas tanah sampai 80,22%, namun pemberian terak baja dan bokashi sekam padi tidak berpengaruh terhadap biomassa tanaman brokoli. Kata kunci : bahan organik, silikat, bobot isi, kemantapan agregat, brokoli

Organic matter supplement is well-known to influence soil aggregate stability (AS), but the corresponding change in recently deposited fine sediment is not documented well. In this study, improvements in aggregate stability of recently deposited sediment supplemented with the farmyard manure (FYM) and tea waste (TW) during 18-week incubation under controlled conditions. The FYM and TW were applied to recently deposited sediment at different doses (0, 2.5, 5, 7.5, 10, 12.5, and 15 % on weight base). The AS was determined at different times after adding organic matter (2nd, 4th, 6th, 8th, 10th, 14th, and 18th weeks) using wet sieving methods. The results showed that aggregate stability of deposited sediment treated with TW was statistically significantly higher than these of samples treated with FYM. Aggregate stability increased with increasing doses of both FYM and TW. In the FYM applied samples, AS reached the highest value at the end of second week, and declined within the following incubation period. However, in the samples treated with TW, AS reached the highest value at the end of eighth week. The results of this study were clearly indicated that tea waste and farmyard manure applications noticeably increased aggregate stability of recently deposited sediment, therefore it is suggested that TW and FYM could be used for structural stabilization of sediments.

National audience; Soil erosion in farmlands is a major cause of water quality degradation and reduced crops production potential throughout the European countries. In agroforests, if the role of tree lines as physical barriers to runoffs is easily understanding, processes involving rooting systems and soil erodilbility are still unknown. Objectives-Do the presence of a tree line improve soil aggregate stability ?

Stabilisation effects of plants are developing as a function of time. Within this scope soil aggregation processes play a decisive role in re establishing a protective vegetation cover. From this perspective we compared bare and vegetated soil on the one hand artificially prepared and on the other hand derived from a recently landslide affected slope and an adjacent gully with 25 year old eco engineering measures respectively. In both cases the planted specimens had a significantly higher soil aggregate stability compared to their respective control samples with the relative increase from control to planted equal for both the natural and artificial samples. Aspects of the development and succession processes of plants are compared as well as rooting and the degree of mycorrhization. Additionally soil development and the methodical approach are discussed as well as a new approach to modelling soil aggregate stability in respect of eco engineering measures for slope stabilisation presented.

The use of treated wastewater (TWW) for agricultural irrigation becomes increasingly important in water stressed regions like the Middle East for substituting fresh water (FW) resources. Due to elevated salt concentrations and organic compounds in TWW this practice has potential adverse effects on soil quality, such as the reduction of hydraulic conductivity (HC) and soil aggregate stability (SAS). To assess the impact of TWW irrigation in comparison to FW irrigation on HC, in-situ infiltration measurements using mini disk infiltrometer were deployed in four different long-term experimental orchard test sites in Israel. Topsoil samples (0-10 cm) were collected for analyzing SAS and determination of selected soil chemical and physical characteristics. The mean HC values decreased at all TWW sites by 42.9% up to 50.8% compared to FW sites. The SAS was 11.3% to 32.4% lower at all TWW sites. Soil electrical conductivity (EC) and exchangeable sodium percentage (ESP) were generally higher at TWW sites. These results indicate the use of TWW for irrigation is a viable, but potentially deleterious option, as it influences soil physical and chemical properties.

Soil erosion in farmlands is a major cause of water quality degradation and reduced crops production potential throughout the European countries. In agroforests, if the role of tree lines as physical barriers to runoffs is easily understanding, processes involving rooting systems and soil erodilbility are still unknown. Objectives-Do the presence of a tree line improve soil aggregate stability ?

Soil aggregate stability (AS) has been promoted as a primary indicator of soil-surface function and a key metric in state-and-transition models. There are few studies, however, that relate indices of AS to the process of grassland degradation. In a Chihuahuan Desert rangeland, we measured variation in AS across vegetated-bare patch boundaries within six plot types reflecting a hypothesized fragmentation/transition sequence. We also examined wetting front depth and pH along this sequence. We found that AS exhibited consistent and interpretable variation across the patch boundaries of the different plot types. Average AS was highest in grass patches adjacent to small to medium-sized (0.5-1.5 m) bare patches and was low in grass patches adjacent to large (> 3 m) bare patches. AS of bare ground was also lowest when bare patches in continuous grassland were large and when bare ground formed an interconnected matrix. Wetting depth after a large storm decreased and pH increased along the fragmentation sequence. The results suggest that AS has interpretable relationships with grassland fragmentation and transitions among states. Careful attention to patchiness within states and stratification, however, is important and simple classifications of strata, such as ‘‘bare interspace’’ and ‘‘plant,’’ may not be sufficient to document variation in soil function.

Arbuscular mycorrhizal (AM) fungi are ubiquitous in agricultural soils. These fungi play important roles in plant nutrition and soil conservation. The persistence of AM fungi in ecosystems depends on the formation and survival of propagules (e.g., spore, hyphae and colonized roots). While spores are considered to be resistant structure that may be view as “long-term” propagules when viable host plants are not present, hyphae are considered to be the main source of inocula when host plants are present and the soil is not disturbed. Tillage is an integral part of modern agriculture that can modify the physical, chemical and biological properties of a soil. Consequently, tillage practices may also affect AM fungi. The various tillage practices used in the management of soil for maximum crop production may negatively impact the survival of AM fungal propagules. In tilled soil, certain AM species may survive while others may disappear. Because AM fungi are more abundant in the topsoil, deep plowing may dilute their propagules in a greater volume of soil, thereby reducing the level of infection of a plant root. Tillage is particularly detrimental to AM hyphae if the soil is tilled in the fall and the hyphae are detached from the host plant. Under no-till (NT), AM fungi survive better, particularly when they are close to the host crop on which they developed. There is speculation that in NT systems, plants may follow old root channels and potentially encounter more AM fungal propagules than plants growing in soil that has been tilled. Management of AM fungi in NT soil is essential to maximizing benefits to crops. This review reports how tillage practices affect AM fungi species richness, survivability and infectivity, and how conservation tillage can increase AM fungi survival, consequently improving plant phosphorus uptake and soil aggregate stability. Key words: Arbuscular mycorrhizal fungi, conservation tillage, conventional tillage, P uptake, soil aggregate stability, cover crops, crop yield

Soil crusting decreases infiltration, increases erosion, and impedes vegetation establishment, so reducing the impact of crusting is of major importance in combating desertification. Although surface crusting has been the subject of considerable research over the past 50 years or more, the practical management of soil crusts remains a challenge for many dryland communities. Crusting occurs in two steps, an initial aggregate breakdown period that occurs under rainfall and a subsequent hardening phase during drying. Several factors influence crust development, but the single most important one is soil aggregate stability. Strategies to reduce crusting can be based either on protecting the surface from raindrop impact or improving aggregate stability, or a combination of both. However, crust control is labor and/or capital intensive and must be thought out clearly in terms of the benefits to be achieved.

The effect of freezing and thawing on wet aggregate stability of soils formed on different parent materials was determined for different aggregate size groups (0.0–1.0; 1.0–2.0; and 2.0–4.0 mm), different water contents and for various freezing and thawing cycles (three, six and nine times) and freezing temperatures (−4 and −18 °C). The initial wet aggregate stability decreased with freeze–thaw treatments by 28.6–51.7% depending on soil type, and was more pronounced with increased moisture contents at freezing. The percent decrease in wet aggregate stability for different aggregate size groups ranged from 13.8% to 57.7%. Wet aggregate stability generally increased when the number of freezing and thawing cycles increased from 3 to 6, but decreased after that point. The percentage of water-stable aggregates in all soils at −18 °C was less than that at −4 °C.

10 páginas, 3 figuras, 4 tablas, 71 referencias.-- Special Issue: Advances Towards an Integrated Assessment of Fire Effects on Soils, Vegetation and Geomorphological Processes, Wildfires represent one of the main factors of land degradation in Mediterranean environments having negative effects to several ecosystem services. In this work, the fire-induced changes associated with depth (O horizon and Ah at 0–1, 1–2 and 2–3 cm depths) were studied in a gypseous soil under Aleppo pine forest. Topsoil monoliths were burned in an outdoor combustion tunnel simulating a fire of moderate intensity. In the O horizon, burning caused an immediate and significant decrease in water repellency (WR), total organic carbon (TOC) and pyrolyzed carbon (PyC) and an increase in total inorganic carbon. The Ah horizon was also significantly affected by fire, but mainly in its first shallower centimetre and with a different direction according to soil properties: TOC, gypsum, WR and PyC decreased, whereas soil aggregate stability and pH increased. Soil burning not only involved the loss of the pre-fire organic matter content of the O horizon and the upper centimetre of the Ah horizon but also decreased their relative abundance of markers of resins, lignin and polysaccharides. Moreover, the soil burning exerted the cracking of alkylic long-chain molecular series, some of them until the 2 cm Ah depth. The reduction of organic lipophilic molecules in the upper soil centimetre may be related to the fire-induced decreases in WR. Moderate burning of the studied gypseous ochric horizon does not modify any of the properties studied at depths greater than 2 cm., This study was supported by the Government of Aragón (Spain) and ‘La Caixa’ (GA-LC-055/2011) and the Spanish "Ministerio de Economía y Competitividad" through project GEOFIRE (ref. CGL2012-38655-C04-01).

Seven case studies are presented, demonstrating the successful use of a laboratory-based drip-screen rainfall simulator at Coventry University to investigate several hydrological, pedological and geomorphological problems. The results of previously unpublished studies are presented in full, while the salient points of published studies are discussed. Synthesis of the experimental results led to the recognition of various philosophical and practical problems associated with the realistic simulation of rain, which need to be addressed in future research. Particular problems are posed by the variety of analytical approaches and simulator designs, as they impede meaningful inter-laboratory comparisons. It is argued that future improvements require optimization, harmonization and standardization of analytical procedures and rainfall simulators. An ideal approach would be the development of a European key laboratory to offer realistic and standardized simulation conditions. Copyright © 2000 John Wiley & Sons, Ltd.

Soil aggregate stability is a crucial soil property affecting soil sustainability and crop production. A broad outline of the processes and agents of aggregate formation and aggregate stabilization are presented and discussed in this review. Aggregate stability is difficult to quantify and interpret. The aim of aggregate stability tests is to give a reliable description and ranking of the behavior of soils under the effect of water, wind and management. Numerous methods have been used to determine aggregate stability with varying success. The different methodologies complicate the comparison among aggregate stability data. It is also difficult to obtain a consistent correlation between aggregate stability and other important soil properties such as soil erodibility or crusting potential. This paper reviews the different methods of measurement of soil aggregate stability used in the literature, paying attention to the conditions of sample collection in the field and sample preparation and treatmen...

Alum was applied at rates of 0.01, 0.02, 0.05, 0.1 and 0.2% by weight to a calcareous silty clay soil in an attempt to reduce soil crusting and improve soil aggregation. Results indicated that the modulus of rupture (MR) was reduced from 176 to 60 kPa with the addition of 0.2% alum. The mean weight diameter (MWD) was doubled when the application rate of alum increased from 0 to 0.2%. Alum apparently modified the soil physical environment by making the soil fluffy which in turn reduces its MR. Gypsum was formed by the reaction of alum with calcium carbonate in proportion to the amount of alum applied, increasing from 0.2% in the control soil to 1.1% with the highest rate of alum applied. This increase may have lead to the reduction in the MR and an increase in the MWD. This research showed that alum was effective in improving soil aggregate stability and decreasing aggregate rupture stress.

Since traditional methods of disposing of oily food wastes have recently lost favor, there is a current search for alternatives. Field-and laboratory-scale experiments examined the decomposition of oily food wastes applied to agricultural lands to examine this disposal option and potential agronomic henefits. Treatment rates of oily food waste equivalent to 3 to 11.3 g of C kg -1 increased soil microbial biomass C in the field hy up to five times control levels. Wet aggregate stability also increased with waste addition and was maintained over the course of the growing season. Laboratory incuhation studies examining the hiodegradation of canola oil and oily food waste showed that the oily fraction of the waste was not rate limiting, and that both suhstrates degraded rapidly with initial decomposition half-lives of 40 to 45 h and 70 to 94 h for canola oil and waste treatments, respectively. The extents of mineralization over 4 wk were up to 84 and 40% for canola oil and oily food waste, respectively. Similar to the field, increases in aggregate stability were measured in the canola oil incubation. Examination of the hiodegradation data indicates two substrate pools are being sequentially decomposed, and that the added substrate is not directly responsible for improved structural properties. The longer lasting binding abilities of microbial products and bodies are the major contributing factors for the increased soil aggregation. It is concluded that the land application of oily food waste is agronomically beneficial by increasing soil microbial activity, and in turn improving soil structure through increased aggregate stability.

The aim of this study was to investigate the effects of biochar amendment on soil aggregate formation and stability, and soil hydraulic properties. Biochar produced from dairy manure was added to two different soils (a silty clay and a sandy loam soil) at a ratio of 2% (w/w in dry weight basis). Incubation experiments were conducted within a 90-d period with the soils (the controls) and the soil/biochar mixtures. Compared with the controls, biochar addition significantly enhanced the formation of macroaggregates and slightly increased saturated hydraulic conductivities of the soils. Attributable to the soil structure change, saturated water contents increased and residual water contents decreased with the biochar amendment. These changes with biochar addition greatly affected the shape of soil water retention functions. For both the soil aggregate formation and the change of soil water retention curves, the sandy loam soil was more sensitive than the silty clay soil to the biochar application on all sampling days. The information from this study should be useful to better understand water processes in the soil with biochar application.

Soil aggregate stability influences a wide range of physical and biogeochemical processes in the agricultural and natural environments, including soil erosion [3]. The relative prepon‐ derance of aggregates of various sizes in the soil and their stability to external forces are, therefore, an issue of major concern to soil scientists. By definition, an aggregate is a compo‐ site body or granule of loosely bound mineral particles within a soil, the binding of which is characteristically mediated by a relatively minor amount of organic matter [Encyclopedia of Soil Science, ESS 2008]. The mineral and organic particles involved in such a natural con‐ glomeration, otherwise known as aggregation, cohere to each other more than to the neigh‐ bouring particles and/or aggregates [ESS 2008]. Soil aggregates are therefore soil structural units of which classical soil research recognizes two major size-based categories, macroag‐ gregates and microaggregates. Collapse of macroaggregates yields microaggregates. Thus, macroaggregates may be viewed as having microaggregates as their building blocks. Some‐ times, external forces acting on a soil can also foster formation of aggregates from dispersed materials. It is the interplay of aggregate formation and breakdown that results in soil struc‐ ture [54]. Although extremities in either of these structure-promoting processes are undesir‐ able, they are considered an agronomic and environmental problem only in the case of breakdown. This is because it is much easier to break down over-sized aggregates into fa‐ vourably sized ones than to achieve aggregation in structurally dilapidated soils. Conse‐ quently, studies on the responses of soil aggregates to natural and anthropogenic forces appear to tilt more towards stability or otherwise of soil aggregates than to their coalescence by these forces. Soil aggregation includes the processes of formation and stabilization, both of which occur continuously and concurrently [3]. Soil aggregate/structural stability may be defined as a measure of the ability of the soil structural units to resist change or the extent to

Agronomijos studijų programos magistro baigiamasis darbas 40 puslapių, 10 paveikslų, 2 lentelės, lietuvių kalba. Tyrimo objektas: paprastojo miežio (Hordeum vulgare L.) vasarinės veislės ,,Simba'' agrocenozė. Tyrimo tikslas: Įvertinti ilgalaikio skirtingo intensyvumo žemės dirbimo poveikį miežių agrocenozei, taikant intensyvias technologijas. Tyrimo uždaviniai: 1. Apžvelgti mokslinę literatūrą ir atlikti sisteminę analizę tiriamuoju klausimu. 2. Aprašyti atlikto eksperimento vykdymo sąlygas ir metodus. 3. Tyrimais nustatyti ir įvertinti ilgalaikio skirtingo intensyvumo žemės dirbimo poveikį struktūros patvarumui, miežių sudygimui, pasėlių piktžolėtumui ir miežių produktyvumui. Tyrimo metodai: mokslinės literatūros apžvalga, loginė analizė ir sintezė, statistinė analizė, palyginamoji analizė, grafinio modeliavimo technikos. Tyrimo rezultatai: • Pirmoji dalis pristato Lietuvos ir užsienio autorių mokslinės literatūros analizę. Mokslinė medžiaga atrinkta, susisteminta ir analizuota. • Antroje dalyje aprašyti koncentruojamasi ties bandymo schema ir parametrais, mokslinio eksperimento variantais ir duomenų analizės stebėjimais ir metodais. • Trečioji dalis identifikuoja dirvožemio struktūros patvarumą, miežių sudygimą ir stiebų produktyvumą, miežių derlių, pasėlių piktžolėtumą bei miežių produktyvumą. Nustatyta, kad ilgalaikis skirtingo intensyvumo žemės dirbimas neturėjo esminės įtakos dirvožemio struktūros patvarumui. Nenustatyta esminės įtakos ir miežių produktyvumui... [toliau žr. visą tekstą] Final work of University Undergraduate/Master Studies 47 pages, 9 figures, 2 tables, the Lithuanian language. Object of the research: barley (Hordeum vulgare L.) spring variety Simba'' agrocenoses. Aim of the research: to evaluate the long-term effect of different soil tillage intensity on barley agrocenosis applying intensive technologies. Objectives of the research: 1. Review of the literature and perform a systematic analysis of the relevant issue. 2. Describe an experiment carried out with the conditions and methods. 3. Studies to identify and evaluate the long-term differences in the intensity of tillage effects on structural stability, barley germination, weed infestation and barley productivity. Research methods: review of scientific literature logical analysis and synthesis, statistical analysis, comparative analysis, graphical modelling techniques. Research results: • Part One presents Lithuanian and foreign scientific literature. Scientific material selected, structured and analysed. • Part Two describe the focus is on testing scheme and the parameters of the scientific variants of the experiment and data analysis methods and observations. • Part Three identifies the soil structure stability, barley germination and stem productivity of barley harvest, weed and barley crop productivity. It was established, that tillage intensity had no significant effect on soil aggregate stability and on barley productivity parameters except the number of germinating barley... [to full text]

9 Pags., 4 Tabls., 3 Figs., Agricultural management practices play an important role in soil organic carbon (SOC) protection within soil aggregates. However, there is a lack of information on the effects of N fertilization on C protection within aggregates under no-tillage (NT) systems. The effects of organic fertilization (with pig [Sus scrofa] slurry and poultry manure) and mineral N fertilization on soil aggregation and physical C protection dynamics under NT soils were investigated. Two experiments were established in a semiarid area of northeastern Spain. In the organic fertilization experiment, treatment with pig slurry at two N rates (100 and 200 kg N ha−1), poultry manure (100 kg N ha−1), and a control (0 kg N ha−1) treatment were compared. In the mineral fertilization experiment, increasing rates of N fertilizer (0, 40, 80, 120, and 160 kg N ha−1) were compared. Water-stable macroaggregates (>0.250 mm) and their C concentration, the distribution of dry-sieved aggregates, total SOC and microbial biomass carbon (MBC) were quantified in the soil surface in two cropping seasons. Organic fertilizers slightly increased the proportion of water-stable macroaggregates but caused no differences in MBC, SOC, or water-stable macroaggregate C concentration. In the mineral N fertilization experiment, similar water-stable macroaggregate, water-stable macroaggregate C and SOC concentrations were observed among N fertilizer doses. Overall differences in water-stable macroaggregates between sampling dates were greater than differences between fertilization treatments. Our study demonstrates that, in the short-term, the use of organic or mineral N fertilizers hardly improves the stability of the macroaggregates and their C protective capacity when NT is performed. This finding could be related to the limitations imposed by water in the Mediterranean areas and the buffering effect of long-term NT adoption on soil aggregate stability and C protection., D. Plaza-Bonilla was awarded an FPU fellowship by the Spanish Ministry of Education. This research was supported by the Comision Interministerial de Ciencia y Tecnología of Spain (AGL 2007-66320-C02-01 and AGL 2010-22050-C03-01).

The work deals with the qualitative modifications of a Calcaric fluvisol after irrigation with fresh water and depurated pig-slurry effluents (aerobic and anaerobic treatment, and phytodepuration with a reed bed system). The accumulation of nutrients (nitrogen and phosphorus) and heavy metals (Cd, Co, Cr, Cu, Ni, Pb, Zn) as total and as bio-available forms in the soil was evaluated, together with soil aggregate stability index, hydraulic conductivity of the saturated soil and the in situ infiltration rate. The experimental field was divided into three plots, and cultivated with silage maize for three years (2003-2005). Results showed that the irrigation with depurated and phytodepurated effluents produced significant changes in the soil chemical properties controlling soil permeability, and influenced the bio-available fraction of heavy metals., L’étude s’intéresse aux transformations qualitatives d’un Calcaric Fluvisol après irrigation avec de l’eau douce et des effluents de porcherie purifiés (traitements aérobie et anaérobie, phyto-épuration avec un système de roselière). On a évalué l’accumulation d’éléments (azote et phosphore) et de métaux lourds (Cd, Co, Cr, Cu, Ni, Pb, Zn) sous formes totale et biodisponible dans le sol, aussi bien que l’index de stabilité de structure des agrégats, la conductivité hydraulique du sol saturé et le taux d’infiltration in situ. Le champ expérimental a été partagé en trois parcelles et cultivé avec du maïs pendant trois ans (2003-2005). Les résultats montrent que l’irrigation avec les effluents purifiés et phyto-epurés a induit des changements significatifs dans les propriétés chimiques du sol qui en régulent la perméabilité et y a modifié la fraction des métaux lourds bio-disponibles., Il lavoro descrive le modifiche qualitative di un Calcaric fluvisol a seguito dell’irrigazione con acqua dolce ed effluenti suinicoli depurati (trattamento aerobico ed anaerobico, e fitodepurazione a flusso verticale). É stato valutato l’accumulo nel suolo di elementi nutritivi (azoto e fosforo) e di metalli pesanti (Cd, Co, Cr, Cu, Ni, Pb, Zn) in forma totale e biodisponibile, l’indice di stabilità di struttura degli aggregati, la conducibilità idraulica del suolo saturo e la velocità di infiltrazione in situ. Il campo sperimentale è stato diviso in tre parcelle e coltivato a mais per tre anni (2003-2005). I risultati mostrano che l’irrigazione con effluenti depurati e fitodepurati ha indotto variazioni significative nelle proprietà chimiche del suolo che ne regolano la permeabilità ed ha modificato la frazione bio-disponibile dei metalli pesanti., EQA - International Journal of Environmental Quality; Vol 5 (2010); 33-42

Humic acids extracted from composted vegetable residues (green compost) or mined lignite (leonardite) have been tested for their influence on either soil cracking or microaggregation characteristics. This preliminary study has pointed out that humates from green compost, within the range of 1000 to 8000 mg kg−1 of soil, induce small-size clod formation in a dose-independent manner and preserve stability of microaggregates. On the other hand, humic acids from leonardite did not improve soil shrinkage and water-stable microaggregates, but rather they determined deterioration of such physical characteristics of the soil tested.

The present paper deals with the long-term effects of bare fallow and organic treatments on soil aggregate stability. Soil samples were collected from plots of the long-term soil organic matter experiment in Ultuna/Sweden, which is already running for 38 years. Soil aggregate stability (SAS) showed a clear response to soil management. SAS increased in following order: bare fa llow < no-N < green manure < peat ≤ farmyard manure. Humus contents of the plots had a significant impact on S AS. Increasing Corg− contents generally enhanced aggregation. However, the unfavourably high C/N ratio of peat treatments and the resulting small size of microbial biomass led to a distinctly lower positive influence of accumu lated soil organic matter in case of peat additions. Uber die Wirkung organischer Dunger auf die Aggregatstabilitat im Dauerfeldversuch von Ultuna Die vorliegende Arbeit beschaftigt sich mit den Langzeitwirkungen von Schwarzbrache und verschiedenen organischen Dungern auf die Aggregatstabilitat einer eutrophen Braunerde. Dazu wurden Bodenproben aus dem Langzeitversuch in Ultuna/Schweden entnommen. Dieser Versuch lauft bereits 38 Jahre. Die Aggregatstabilitat zeigte einen signifikanten Einflus der verschiedenen Behandlungen. Sie stieg nach folgender Reihung an: Dauerschwarzbrache < keine Stickstoffdungung < Grundungung < Torf < Stallmist. Die Aggregatstabilitat war gut mit den Humusgehalten der Parzellen korreliert. Steigende Corg− Gehalte fuhrten zu einer hoheren Stabilitat der Aggregate. Allerdings fielen dabei die Torfparzellen aus dem Rahmen. Aufgrund des ungunstig weiten C/N-Verhaltnisses und der damit verbundenen wesentlich geringeren mikrobiellen Biomasse hatte der Humus der Torfparzellen eine deutlich schwachere positive Wirkung auf die Aggregierung.

Soil structure is often severely affected during high intensity burning, while low intensity prescribed burning has often been thought to have a low or neutral effect on soil aggregation. In this issue of Plant and Soil, (Albalasmeh et al. 2012) report a novel mechanism of aggregate disruption during low intensity burning that may explain some contradictory results reported in previous studies. Albalasmeh et al. (2012) suggest that during rapid heating of moist soil aggregates, intra-aggregate water is vaporized and the increased pressure causes rupture of the internal bonds and leads to aggregate breakdown. This mechanism can be compared to the aggregate breakdown due to slaking, when dry aggregates are suddenly wetted or submerged in water. Identification of the reasons for the aggregate disruption at low temperatures is important for choosing optimal soil and weather conditions for prescribed fires.

Soil samples from an experimental field were investigated. The aggregate stability using the wet sieving method and the water drop technique as well as the soil erodibility using a rainfall simulator was calculated. Since it was found that the soil erodibility increases with increasing soil aggregate stability due to the problem of relativity imposed by the aggregate diameter, subsequently, some modifications were introduced to restore the normal trend.

According to the method for estimating soil aggregate stability (SAS) described by Kemper and Koch, a new sieving device has been constructed to improve manipulation and the rapidity of the analysis. The method of determination is described. Multiple replications of several samples that have been carried out by the members of the Austrian Soil Physics Research Group, showed a small standard deviation on the same soil samples. Storage of soil samples before measuring may cause a variation (increase) in SAS. The spatial variability of SAS on three field plots turned out to be relatively low. However, statistically significant differences were obtained, which proofs the high precision of the modified machine. Furthermore a significant influence of cattle slurry treatments on SAS of permanent grassland soil could be detected.

This study had the purpose of evaluating the effects of two management types of sugarcane: harvesting of burnt cane (BCH) and mechanized harvesting of unburnt green cane (MCH), on some soil physical properties of a dystrophic Rhodic Haplustox. The data were then compared with results for the same soil type under native forest. A completely randomized design was used, with three treatments and 20 replications. The following characteristics were determined: organic matter, aggregate stability, soil bulk density, and porosity at depths of 0-0.20 m and soil penetration resistance. After 15 years of cultivation, there were some alterations in the soil under cane burnt before harvesting, evidenced by a drop in the weighted average diameter of stable aggregates in water and increased soil bulk density. Significant changes were also detected in total porosity and pore distribution under both harvesting systems. Critical values for penetration resistance were observed in the area under mechanized sugar cane harvesting, with a value of 4.5 MPa in the 40-55 cm layer. This value is considered high and could indicate compaction and restriction of root growth. Soil properties under the green cane (unburned) management system were closest to those of the soil under native forest. Este trabalho foi conduzido em Latossolo-Vermelho distrófico, sob cultivo de cana-de-açúcar, com o objetivo de avaliar o efeito de dois sistemas de manejo, com (CCQ - corte manual de cana queimada com carregamento mecânico) e sem queima (CSQ - colheita mecânica de cana picada, crua), sobre propriedades físicas do solo. Os dados foram comparados com os resultados do mesmo solo sob mata nativa. O delineamento utilizado foi o inteiramente casualizado, com três tratamentos e 20 repetições. Foram determinadas a matéria orgânica, estabilidade de agregados, densidade e porosidade do solo, na profundidade de 0-0,20 m, e a resistência do solo à penetração. Após 15 anos de cultivo, constatou-se alteração do solo no sistema CCQ, evidenciada pela diminuição do diâmetro médio ponderado dos agregados estáveis em água e pelo aumento da densidade do solo. Foram também detectadas alterações significativas na porosidade total e distribuição de poros, devido às práticas de manejo nos dois sistemas de colheita. Valores críticos de resistência à penetração foram observados na área de cana mecanizada (CSQ), a 0,40-0,55 m de profundidade, sendo o valor (4,5 MPa) classificado como alto, podendo indicar compactação e restrição ao crescimento radicular. O manejo mecanizado foi o sistema que apresentou características do solo mais próximas às da área de mata nativa.

4 Pag., 3 Fig., Conservation tillage is particularly important in arid and semi-arid zones, where water is the limiting factor for crop development under rainfed conditions. Conservation tillage improves physical properties and increases organic matter of soils under Mediterranean conditions. This work studies the influence of two tillage systems (traditional tillage, TT, and conservation (reduced) tillage, RT) on soil hydraulic properties and on soil aggregation after 15 years of experimentation. The effect of no-tillage (NT) in a short-term experimentation (4 years) was also considered. In the long-term experiment, the aggregate size distribution (ASD), mean weight diameter (MWD) and aggregation index (AI) values were greater in RT than in TT, although differences were not significant. Water stability (WAS) values for 1-2 mm size aggregates were greater in TT, despite the organic carbon (OC) and CaCO3 contents in these aggregates were greater in RT. However, under our conditions NT seems to have a greater effect on WAS. The increase of this variable in NT respect to TT, was observed after only three years of experimentation. In the long-term experiment, the hydraulic conductivity was higher in TT than in RT for h > -20 mm in agreement with a greater characteristic mean pore radius for h > -20 mm. In the short-term experiment, the lower hydraulic conductivity in NT than in TT suggests a lack of interconnected pores in NT treatment.

International audience; Soil aggregate stability is a key indicator for soil quality evaluation.The transition area from forest to grassland zone of the Hilly-gully region,located in Yangou Catchments in Yan'an City,was taken as a research site.Soil samples from six vegetation types during vegetation natural restoration were used to measure soil water-stable aggregate using Le Bissonnais(LB) method,and compared the results of LB 3-treatments with the Yoder method.The results showed that,in the 3-treatments(fast wetting,slow wetting,and wetting stirring) of LB method,fast wetting(FW) was the most destructive degree to the soil aggregate stability,the distribution of soil water-stable aggregate mainly concentrated in 0.05-0.5 mm;slow wetting(SW) was the least destructive degree to soil aggregate stability,soil water-stable aggregate content was mainly >2 mm;the destructive degree of soil aggregate structure by wetting stirring(WS) was between FW and SW treatments,the soil water-stable aggregates size was well-distributed.It was explained that the primary destructive mechanism of soil aggregate structure was dissipation.During the period of 100a of abandoning cropland,the succession process of vegetation experience is annual herbaceous(4 a)—perennial herbaceous(16 a)—semi shrub(29 a)—shrub(55 a)—arbor(100 a).With the succession process of vegetation,soil water-stability aggregate size shifted from small size to large size,soil structure was improved.The correlation between >0.5 mm soil aggregate content or mean weight diameter(MWD) measured by FW or SW and soil organic carbon or physical clay content was significantly different;but for WS treatment,there was no significant different between soil aggregate content or MWD and soil organic carbon or physical clay content.This result showed that soil organic matter and physical clay content mainly influenced dissipation and disintegration by clay swelling and mechanical stirring had no significant impacts on soil aggregate stability.Comparing with the Yoder method,SW and Yoder method have highly comparability,and SW treatment of LB method was suitable to measure soil water-stable aggregate during vegetation restoration in the Hilly-gully region.

Slow water infiltration in some California soils results in considerable irrigation water loss through increased runofff and evaporation. This 25-mo study was conducted to evaluate the effects of different organic amendments on soil physical parameters and water filtration rates on an irrigated soil. Incorporation of three loadings (25 Mg ha −1 each) of poultry manure, saewage sludge, barley straw (Hordeum vulgare L.), and alfalfa (Medicago sativa L.) to an Arlington soil (coarse-loamy, mixed, thermic Haplic Durixeralf) for 2 yr increased soil respiration rates (139-290%), soil aggregate stability (22-59%), organic C content (13-84%), soil saccharide content (25-41%), soil moisture content (3-25%), and decreased soil bulk density (7-11%) (...)