Method For Aggregate Stability Research Articles

Cross‐correlating soil aggregate stability methods to facilitate universal interpretation

Cross‐correlating soil aggregate stability methods to facilitate universal interpretation

SHAPEv1.0 Scoring curves and peer group benchmarks for dynamic soil health indicators

AbstractThe soil health concept has evolved over the past several decades, recognizing that the response of dynamic soil properties to management is dependent on site‐specific factors. The Soil Health Assessment Protocol and Evaluation (SHAPE) tool provides scores and benchmark values by forming soil peer groups based on site‐specific, climate‐edaphic characteristics. Data for model development were compiled from the Cornell Soil Health Laboratory and the Kellogg Soil Survey Laboratory databases. The SHAPEv1.0 interpretation curves produce scores between 0% and 100% for measured laboratory values that reflect the quantile within a population conditional cumulative distribution function along with measures of uncertainty. The original SHAPE tool was developed for soil organic carbon and has been expanded to include two wet aggregate stability methods, permanganate oxidizable organic carbon, autoclaved citrate extractable protein, and 4‐day microbial respiration. In addition, SHAPE provides site‐specific benchmark values at user‐defined percentiles within a given soil peer group. The difference between the actual measured value and the selected benchmark value represents the soil health opportunity gap. Case studies in Missouri and Texas show that the SHAPE scoring curves are sensitive to land‐use and management practices across multiple soil types and provide a regionally relevant interpretation of key soil health indicators.

Evaluation of aggregate stability methods for soil health

Aggregate stability is a commonly used indicator of soil health because improvements in aggregate stability are related to reduced erodibility and improved soil–water dynamics. During the past 80 to 90 years, numerous methods have been developed to assess aggregate stability. Limited comparisons among the methods have resulted in varied magnitudes of response to soil health management practices and varied influences of inherent soil properties and climate. It is not clear whether selection of a specific method creates any advantage to the investigator. This study assessed four commonly used methods of measuring aggregate stability using data collected as part of the North American Project to Evaluate Soil Health Measurements. The methods included water stable aggregates using the Cornell Rainfall Simulator (WSACASH), wet sieved water stable aggregates (WSAARS), slaking captured and adapted from SLAKES smart-phone image recognition software (STAB10), andthemean weight diameter of water stable aggregates (MWD).Influence of climate and inherent soil properties at the continental scale were analyzed in addition to method responses to rotation diversity, cash crop count, residue management, organic nutrient amendments, cover crops, and tillage. The four methods were moderately correlated with each other. All methods were sensitive to differences in climate and inherent soil properties between sites, although to different degrees. None measured significant effects from rotation diversity or crop count, but all methods detected significant increases in aggregate stability resulting from reduced tillage. Significant increases or positive trends were observed for all methods in relation to cover cropping, increased residue retention, and organic amendments, except for STAB10, which expressed a slightly negative response to organic amendments. Considering these results, no single method was clearly superior and all four are viable options for measuring aggregate stability. Therefore, secondary considerations (e.g., cost, method availability, increased sensitivity to a specific management practice, or minimal within-treatment variability) driven by the needs of the investigator, should determine the most suitable method.

Evaluation of Aggregate Stability Methods for Soil Health

Evaluation of Aggregate Stability Methods for Soil Health

Quantitative and qualitative comparison of three wet aggregate stability methods using a long-term tillage system and crop rotation experiment

Automated wet-sieving is preferred for this clay loam soil due to better sensitivity and savings (time and disposables) despite a larger capital investment. Rotations with greater frequency of winter wheat and no-till compared with conventional plow system had greater wet aggregate stability values, indicating better surface soil quality.

Soil structure breakdown following land use change from forest to maize in Northwest Vietnam

Conversion of forest to agricultural land for maize cultivation is known to negatively affect soil fertility. However, limited knowledge is available of the impact on aggregate stability and interconnected soil properties. The aims of the present study were to (1) quantify soil aggregate stability, (2) assess aggregate stability changes after land use change, and (3) determine the interactions of aggregate stability with clay, soil organic carbon (SOC), exchangeable Ca2+ and Mg2+, and soil erosion rates. The topsoils of three soil types in Northwest Vietnam were analyzed in chronosequences (0–18 y after land use change from forest to continuous maize) by two methods: Wet sieving and sonication. By differentiation of these aggregate stability measurements, the impact of both methods on aggregate size distribution could be quantified separately and compared. The sonication method indicated a more homogeneous disaggregation whereas the wet sieving method was more suitable to detect low aggregate stabilities. Soil aggregate stability declined simultaneous with a decrease of SOC and exchangeable Ca2+ and Mg2+, which both declined with increasing time since land use change. The Alisol and Luvisol chronosequences were 1.9 times more stable under primary forest than under maize (shown by sonication) whereas the Vertisol chronosequence was 2.5 times more stable under primary forest (shown by wet sieving). Over the 18 y chronosequence the topsoils had 1.6kgm−2 lower SOC and 3.2gkg−1 lower Ca2+ contents. This study highlights the destabilization of soil in interaction with a degradation of relevant chemical soil properties with differentiated aggregate stability methods.

Fire changes the larger aggregate size classes in slash-and-burn agricultural systems

The slash-and-burn agricultural system is one of the oldest types of no-tillage soil management. However, farmers using fire may cause unintentional damage to soil structure in the slash-and-burn system. Herein, it is assumed that larger soil aggregates (≥2.0mm to<8.0mm) are the most affected by fire, with direct impacts to their structural stability. An experimental fire was carried out, and the rainfall simulation approach for a period of 30min with a rainfall intensity of 58mmh−1 was used to assess the effects of fire on soil aggregate stability. The macro-aggregate stability was evaluated for the test plot as well as an undisturbed soil sample using two aggregate sizes: 2–4mm and 4–8mm. The fire temperature measured at the soil surface was very high (673±93°C). Consequently, the soil structural stability under the slash-and-burn agricultural system rose significantly. Larger aggregates of ≥2.0mm or ≥4.0mm size indicated a clear influence of fire on soil physical properties. The fire temperature dramatically changed the distribution of the aggregates of ≥4mm, since aggregates of this size were more frequent (51%) and stronger compared to unburned soil. The methodology is critical to detect the changes in the physical properties of aggregates affected by fire. Aggregate stability methods using a single sieve of ≥0.25mm over rainfall simulation, but without consideration of the completely fragmented particles remaining in the sieve, were not able to detect the aggregation changes.

Comparison of Aggregate Stability Measurement Methods for Clay‐rich Soils in Asartepe Catchment of Turkey

AbstractThere are many methods and approaches of determining the structural status of soils as a quality indicator. But there is no common method for aggregate stability measurement that can be used for all soil types and circumstances affecting aggregate disruption. This study aimed to compare different aggregate stability methods for clay‐rich soil systems of semi‐arid lands, where desertification is a significant threat to land resources. The study area is located in the Asartepe catchment of Ankara, Turkey, mainly including land use types of secondary forest, grassland and rainfed arable land. Four research methods were tested: (1) fast wetting (FW); (2) slow wetting (SW); (3) mechanical breakdown (MB) and (4) multiple sieve separation process (MSSP). For clay rich soils (C% ≥ 38) with different land use types in the semiarid region, it was found that MSSP has a greater potential for soil aggregate stability differences to statistically reflect slight variations in SOC than FW, SW and MB. Although the research specifically includes the results from certain land uses and soil types, it is not limited to those but should provide useful findings to help interpret the impairment of soil structural stability differences under various management systems and the processes that each methodology tries to reproduce in a close linkage to given soil properties. Copyright © 2015 John Wiley &amp; Sons, Ltd.

English

Soils from semi-arid environments have traditionally been considered to have poorly stable aggregates. The use of aggregate stability methods for erosion research seems of particular interest. However, its use to predict crusting and erosion have yielded conflicting results. In this study, we investigate the possible relations between aggregate stability and soil physical properties, and soil water erosion parameters using the mean weight diameter concept, based on dry and wet sieving method. We introduced also a new aggregate stability parameter based on the stability quotient which takes into account the percentage of soil fraction larger than 2 mm. Twenty soil sites were sampled from a Mediterranean semi-arid watershed for aggregate stability test. This study is part of a research work about erosion processes in semi-arid regions of Tunisia conducted during the period 1999 to 2013. Results indicate a correlation between aggregate stability indices and quotients with organic matter content (r = 0.70), a positive correlation with clay content (r = 0.30), but a negative correlation with the amount of soil loss and splash (r = -0.49 and r = -0.40 respectively) as collected in a laboratory rainfall simulation experiment. The stability quotient is the best soil parameter that explains soil erosion. It shows that more than 80% of the soil samples have poor structure stability. The fractal dimension, a characteristic property of the number-size distribution of fragments as a mass of material is broken down, was calculated for all soil samples. After wet sieving all samples follow the law of fractal dimensions. &nbsp; Key words: Aggregate stability, erosion, rainfall simulation, stability quotient, fractal analysis.

Comparing Aggregate Stability Tests for Soil Physical Quality Indicators

AbstractAlthough there is not a sole satisfactory methodology that applies universally up to now, aggregate stability has been proposed as an indicator of soil physical quality (SPQ). Difficulties persist when comparison of aggregate stability from different procedures are performed. The objective of this study is to evaluate appropriate aggregate stability methods that enable to distinguish the SPQ condition of both temperate and tropical medium‐textured soils. Among different methods tested, results show that wet sieving using the well known fast wetting methods of Kemper &amp; Rosenau and of Le Bissonnais rendered similar results in both environments. The mean weight diameter value of both methods for assessing aggregate stability can be considered as a dependable indicator of soil structure status for comparing soils. These aggregate stability methods are in correspondence with only one out of the eight SPQ indicators when entirely soils were used. It was concluded that the aggregate stability should be used judiciously and in concert with other indicators for an overall assessing of the SPQ condition. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Comparison of different aggregate stability approaches for loamy sand soils

The bio-dynamic relations of soil aggregate stability, as a widely accepted soil quality indicator, with the physical, chemical and biological soil properties are very complicated in the soil system, and there exist many methods of measuring the soil aggregate stability to establish these relations. This study aimed to evaluate different aggregate stability methodologies for loamy sand soils. The applied aggregate stability methods of the research chiefly involved sieving soil samples through either multiple sieves or a single sieve using operations of wet sieving, dry sieving, pre-wetting, slow wetting, fast wetting and mechanical breakdown. These were used either alone or in combination, and the methods were compared in terms of a detachability index (DI), which is the ratio of the Mean Weight Diameter after wet sieving (MWDW) to that before wet sieving (MWDD). The statistical analysis showed that the mean values of the DI for wet sieving by multiple sieves, fast wetting and mechanical breakdown varied significantly (*P<0.05) from other methods. Clearly, depending upon the magnitude and extent of aggregate destructive forces, the DI changed significantly, and simulating diverse physical processes which could operate sequentially or simultaneously resulted in different consequences in terms of the aggregate stability.

Erodibility of Mediterranean vineyard soils: relevant aggregate stability methods and significant soil variables

SummaryThe extension of viticulture on hill slopes in the Mediterranean basin might be responsible for a loss of organic carbon from the soil, as a result of increasing runoff and erosion. The loss of C makes soil aggregates less stable, which in turn increases erosion risk. We should use indicators of these risks and so be able to identify the most threatened areas. We first tested four widely used methods for determining aggregate stability for their ability to predict runoff and erosion; all include slaking and give indices such as rates of stable (&gt; 200 μm) macro‐aggregates (MA200) or mean weight diameter (MWD). We selected three Mediterranean vineyards characterized by brown calcareous soils and on which we had previously studied the effects of simulated rainfall. The tests were made on the soils from five farming situations, corresponding to 14 simulated rainfalls with an intensity of 60 mm hour−1. The two indices that best predict erosion are those resulting from the method of Le Bissonnais (MWD in its logarithmic form and MA200). Then, we analysed the relations between aggregate stability and soil properties on 68 soil samples from various locations within the three selected sites. A very significant correlation between the two indices of Le Bissonnais’s method and soil organic carbon content was found and we propose a pedotransfer function linking these indices to soil characteristics. The results stress the need for farming practices that preserve the organic C in Mediterranean vineyard soils in order to reduce erosion risks. We believe that our findings might well apply to similar soils elsewhere in the world.Erodibilité des sols de vigre Méditerranéens: Mesure de la stabilité structurale et caractéristiques déterminantes des solsRésuméLe développement de la viticulture sur les sols en pente du bassin Méditerranéen pourrait entraîner une diminution de la teneur en C de ces sols et une aggravation du ruissellement et de l’érosion. La perte de C rend les agrégats moins stables, ce qui augmente le risque d’érosion. Des indicateurs de ces risques sont nécessaires afin d’identifier les surfaces les plus menacées. Nous avons dans un premier temps comparé quatre méthodes différentes, couramment utilisées pour mesurer la stabilité structurale des sols afin d’évaluer leur capacitéà prédire le ruissellement et l’érosion; toutes mettent en jeu de l’éclatement des agrégats et produisent des indices tels que la proportion de macroagrégats stables &gt; 200 μm (MA200) ou le diamètre moyen pondéré des agrégats stables (MWD). Nous avons choisi trois vignobles méditerranéens, caractérisés par des sols bruns calcaires. Les tests de stabilité structurale ont été réalisés sur les sols de cinq sites cultivés, correspondant à 14 simulations de pluie avec une intensité de 60 mm heure−1. Nous avons trouvé des relations significatives entre la stabilité structurale et le comportement lors d’une pluie simulée, les deux meilleurs prédicteurs de l’érosion étant les indices MWD logarithmique et MA200 issus du test de Le Bissonnais. Dans un deuxième temps, nous avons analysé les relations entre ces indices et les caractéristiques de 68 échantillons de sols dans les 3 sites étudiés. Nous avons trouvé une relation hautement significative entre les deux indices et la teneur en C des sols et nous proposons une fonction de pédotransfert reliant ces indices aux caractéristiques des sols. Nos résultats montrent le besoin de pratiques culturales préservant la teneur en C des sols de vignobles Méditerranéens afin de limiter les risques d’érosion.

Aggregate stability kit for soil quality assessments

Aggregate stability affects soil strength and, therefore, the soil's ability to transmit liquids and gases, which are important functions for crop production and ecosystem health. Because aggregate stability is an indicator of vital soil functions, it can be used to assess soil quality. For soil quality assessments, there is a need for a quantitative field method for measuring aggregate stability that is simple to perform, low cost, and available for routine assessments by land managers. A method is presented that follows the commonly used or standard single-sieve wet-sieving method for aggregate stability. A combination of manual sieving and drying apparatus is constructed from a trunk-style tackle box. Sieves are constructed from a 60-mesh screen and PVC reducing adapters. The method requires manual sieving, 30 cycles per minute (0.5 cycles/s) for 3 min. Percent water aggregate stabilities from the proposed manual sieving technique were not significantly different from aggregate stabilities obtained from the mechanical wet sieving technique. The proposed low cost method was able to distinguish differences in aggregate stability caused by differences in soil type and land use. This low cost method provides a tool that can be used in conjunction with other measurements to assess relative differences in soil quality.