Decrease In Aggregate Stability Research Articles

Impact of freeze–thaw cycling on the stability and turnover of black soil aggregates

During freeze–thaw cycling, aggregates undergo a dynamic change in breakdown–formation (turnover), however, how the turnover occurs between aggregates of various particle sizes is not clear. To clarify the influence of freeze–thaw cycling on the dynamic changes in the particle size of soil aggregates, soil aggregates from the Black Soil Region of Northeast China were selected as the research objects. The study conducted in situ dynamic monitoring experiments, innovatively applying the rare earth oxide (REO) tracer method to natural conditions of freeze–thaw cycles (autumn freeze–thaw period, freezing period, and spring freeze–thaw period), accurately tracking the turnover paths and quantifying the turnover rates between aggregates of various particle sizes. The results revealed that the total value of the formation paths of the 2–5 mm aggregates and 0.25–2 mm aggregates increased during the autumn freeze–thaw period. The number of freeze–thaw cycles and accumulated snowfall were significantly positively correlated with aggregate stability, with an increase in the number of freeze–thaw cycles and accumulated snowfall resulting in an increase in the proportion of aggregates > 0.25 mm, which improved aggregate stability. In addition, the total value of the breakdown path of macro-aggregates increased during the spring freeze–thaw cycling period. Soil moisture was significantly negatively correlated with aggregate stability, with increased soil moisture resulting in a decrease in the percentage of aggregates > 0.25 mm, which resulted in a decrease in aggregate stability. The study can provide a reference understanding for the effects of freeze–thaw cycles on the structure of black soil and provide a theoretical basis for improving the quality of arable land.

Impact of polyamide microplastics on riparian sediment structures and Cd(II) adsorption: A comparison of natural exposure, dry-wet cycles, and freeze-thaw cycles

Microplastics (MPs) accumulation in sediments has posed a huge threat to freshwater ecosystems. However, it is still unclear the effect of MPs on riparian sediment structures and contaminant adsorption under different hydrological processes. In this study, three concentrations of polyamide (PA) MPs-treated sediments (0.1%, 1%, and 10%, w/w) were subjected to natural (NA) exposure, dry-wet (DW) cycles, and freeze-thaw (FT) cycles. The results indicated that PA MPs-added sediment increased the micro-aggregates by 10.1%−18.6% after FT cycles, leading to a decrease in aggregate stability. The pH, OM, and DOC of sediments were significantly increased in DW and FT treatments. In addition, the increasing concentration of PA MPs showed an obvious decrease in aromaticity, humification, and molecular weight of sediment DOM in FT treatments. Also, high level of MPs was more likely to inhibit the formation of humic-like substances and tryptophan-like proteins. For DW and FT cycles, 0.1% and 1% PA MPs-treated sediments slightly increased the adsorption capacity of Cd(II), which may be ascribed to the aging of MPs. Further correlation analysis found that DW and FT altered the link between DOM indicators, and aggregate stability was directly related to the changes in sediment organic carbon. Our findings revealed the ecological risk of MPs accumulating in riparian sediments under typical hydrological processes.

Time of aggregate destruction as a parameter of soil water stability within an agricultural hummocky moraine landscape in northern Poland

Slaking is a rapid wetting of soil aggregates that affects their stability in the face of the effects of water. The aggregate’s stability has an indirect influence on soil functioning through its minimising of soil erosion. Testing slaking is very simple, does not need additional complicated equipment and could be done for any point. Testing was performed for natural air-dry aggregates (7–10 mm) sampled from the arable layers of four different types of soils within a young hummocky moraine landscape: Eutric Regosol (Protocalcic), Haplic Luvisol (Protocalcic), Albic Luvisol, Mollic Gleysol. The soil tests were performed on a soil-erosive catena located in Chełmno Lake District (Northern Poland) from the tops of hummocks and from the shoulder to bottom part of depressions. The test results demonstrated a significant decrease in aggregate stability from Mollic Gleysol to Eutric Regosols (Protocalcic) – that is, from colluvial soils at depressions to completely eroded hummock-top soils. However, 75% of all aggregates in Eutric Regosols were unstable when time of aggregate destruction was less than 300 sec. Oppositely to Eutric Regosols laying on hummock tops, 70% of aggregates of Mollic Gleysols in depressions were water stable. The mean time for aggregate destruction for each soil from hummock-top to depression was 209 sec. for Eutric Regosol, 375 sec. for Haplic Luvisol, 616 sec. for Albic Luvisol and 772 sec. for Mollic Gleysol. The main soil properties that affected the time of aggregate destruction are clay content (very strong negative correlation; r=–0.72); soil organic carbon content (strong positive correlation; r=0.69), and content of secondary carbonates (strong negative correlation; r=–0.69).

ANALISIS STABILITAS AGREGAT DAN SIFAT FISIK TANAH DENGAN PENAUNG BERBEDA PADA SISTEM AGROFORESTRI DI LAHAN KOPI SUMBERMANJING WETAN, KABUPATEN MALANG

One of the damages that can occur in the soil structure is a decrease in aggregate stability. This study aimed to analyze the relationship between the stability of soil aggregates on a land by considering the level or type of land cover and the influence of several physical properties of the soil on coffee grounds. In this study there were four treatments with five replicates using a randomized block design at 2 depths, namely 0-20 cm deep and 20-40 cm deep. The treatments were based on different types of shade plants, namely P1 (cocoa shade), P2 (sengon shade), P3 (lantoro shade), and P4 (gamal shade). The results showed that lowest and highest soil aggregate stability values at the top depth (0-20 cm) were found in treatment P1 (cocoa shade) of 1.76 mm and P4 (gamal shade) of 3.33 mm. While at the depth of 20-40 cm, the highest and lowest values were found in the treatment P3 (lamtoro shade) of 1.92 mm and P1 (cocoa shade) of 2.37 mm. The stability of soil aggregates significantly affected soil bulk density, specific gravity, porosity, and organic matter. All treatments gave a significant effect on the thickness of the litter. The highest and lowest values were found in the treatment P4 (shade gamal) and P2 (shade sengon) of 3.4 cm and 1.7 cm, respectively.

How relationships between soil organic matter parameters and soil structure characteristics are affected by the long-term fertilization of a sandy soil

Refining our understanding of how soil structure develops is important because soil structure has a major influence on plant growth. Recent studies show positive correlations between soil organic matter and soil structure. However, the question remains: how are the relationships between soil organic matter (SOM) parameters and soil structure characteristics affected by the long-term fertilization of a sandy soil? In contrast to most other studies on SOM vs. soil structure, the present study is composed of long-term field experiments (a total of 3 experiments) with durations of 25, 41 and 94 years. In this paper, the impact of the long-term application of mineral fertilizers and manure on the SOM and soil structure of a sandy soil is quantified, and the relationships between the SOM and soil structure of a sandy soil with a dependence on the length of fertilizer application are determined. Soil samples were collected from all three long-term field experiments in central Poland, which were located at Skierniewice experimental station including a 94-year-old experiment with mineral fertilization, a 41-year-old experiment with mineral fertilization and a 25-year-old experiment with mineral fertilization + farmyard manure (FYM) in a 4-year cycle. In the spring of 2017, soil samples were collected (Co – no fertilizers, NPK – NPK fertilizers, CaNPK – CaNPK fertilizers). In the 94-year-old experiment, the content of soil organic carbon (SOC) in Co, NPK and CaNPK was 4.07, 5.89 and 5.99 g kg−1, respectively. An increase in the SOC content under fertilization was also found in the other two experiments. In the 25-year-old experiment, the SOC contents in FYM, FYM + NPK and FYM + CaNPK were 6.07, 8.36 and 7.63 g kg−1, respectively, and in the 41-year-old experiment, the SOC contents in Co, NPK and CaNPK were 6.38, 10.1 and 7.80 g kg−1, respectively. The content of labile carbon (CL) increased significantly in the fertilized treatments only in the 94-year-old experiment. The contents of humic substances significantly increased in the soil of fertilized treatments in the 25- and 41-year-old experiments. In all fertilized treatments, the humus quality significantly decreased. After 94 years of mineral fertilization, the content of water-stable macroaggregates (WSAma) in size fractions > 5 and 5–2 mm was significantly higher in the NPK than in the Co and CaNPK treatments. After 94 years of mineral fertilization, the mean weight diameter of aggregates for dry sieving (MWDd) differed between Co (0.41) and both treatments of mineral fertilization (NPK: 0.88; CaNPK: 1.70). The application of FYM with CaNPK resulted in a statistically significant decrease in aggregate stability (Sw) in the 25-year-old experiment. For Co and NPK treatments in the 41-year-old experiment, the contents of WSAma > 5 mm were 41% and 51% lower, respectively, whereas the content of WSAma 5–3 mm was lower by 40% and 50%, respectively, which was higher than that for the CaNPK treatment. The aggregate stability significantly decreased due to NPK application in the soil of the 41-year-old experiment. The number of correlations between SOM parameters and the soil structure decreased in the following order: 94-year-old experiment with mineral fertilization > 41-year-old experiment with mineral fertilization > 25-year-old experiment with mineral fertilization + FYM.

Short-term effects of treated wastewater irrigation on Mediterranean calcareous soil

Water shortage and soil degradation are the two most important environmental problems in the Mediterranean area. For this reason, strategies for soil and water conservation are necessary. Our objective was to evaluate the use of treated wastewater as an irrigation source to help alleviate these problems. Short-term effects on several soil fertility properties were evaluated in an agricultural area located at Biar (Alicante, SE Spain), where grapes ( Vitis labrusca) are grown. Three treatments: fresh water (control), and treated wastewaters from secondary and tertiary treatment were evaluated for 2 years. We found a slight increase in soil organic carbon content in plots irrigated with the secondary treatment. These plots also had increased electrical conductivity (EC) and increased available Na content due to the high values of EC in wastewater. Laboratory analyses also show a decrease in aggregate stability for all treatments, presumably due to the wetting and drying (WD) cycles associated with each irrigation dose. These WD cycles may also explain changes in microbial biomass carbon and basal soil respiration. We recommend modifying the dose of irrigation in order to reduce the quantity applied and to increase the frequency of application to avoid the loss of aggregation. We also suggest long-term studies to assess the feasibility of wastewater reuse.

Distribuição de agregados e carbono orgânico em um Argissolo Amarelo distrocoeso em diferentes manejos

O objetivo principal deste estudo foi avaliar a estabilidade e a distribuição de agregados em um Argissolo Amarelo distrocoeso comparando-se os valores de uma área de mata nativa (MA), com três áreas cultivadas com cana-de-açúcar sendo uma sem irrigação (MSI), uma com irrigação (MCI) e outra sob fertirrigação com vinhaça (MCV). O solo das três áreas cultivadas foi submetido ao mesmo tipo de preparo: gradagem pesada, gradagem leve e subsolagem. Amostras de solo com estrutura indeformada na área de mata e de cada área cultivada foram coletadas para determinação da estabilidade de agregados, expressa pelo diâmetro médio ponderado (DMP), índice de estabilidade de agregados (IEA), módulo de finura (MF), porcentagem de agregados estáveis em água com diâmetros maiores que 2,0 mm (AGRI) e valores de carbono total. Os distintos tipos de manejo do solo com cana-de-açúcar promoveram perda da estabilidade de agregados com o aumento da profundidade. A estabilidade de agregados foi reduzida em relação à mata nativa na sequência: MA > MCV > MCI > MSI. Registraram-se, na área sem irrigação (MSI) os menores índices de agregação, em que na submetida a fertirrigação com vinhaça (MCV) os valores foram semelhantes aos da área de mata nativa apresentando maior índice de estabilidade de agregados em água. Correlações significativas e positivas foram obtidas entre carbono orgânico total e os índices de agregação do solo (DMP > AGRI > MF > IEA) sob diferentes situações de manejo.

Short‐Term Reducing Conditions Decrease Soil Aggregation

Upland soils in the midwestern United States are often ponded during the spring for days or weeks and may undergo reduction. Short‐term reducing conditions change the chemistry of the soil and that may affect soil aggregation. The objective of this study was to determine how changes in the redox status of the soil under a set of controlled temperature and light conditions can impact soil aggregation during short‐term flooding conditions. A biogeochemical reactor was built to achieve reducing conditions. Six different soils, three cultivated and three uncultivated, with different organic C contents were incubated (1:1.5 soil/water ratio) in the reactor for 1 h and 1, 3, 7, and 14 d. After each treatment, the soil solution was collected and analyzed for metals and dissolved organic C (DOC). A high‐energy moisture characteristic procedure was used to determine the aggregate stability of the incubated soil samples. A strong correlation was found between changes in the redox potential (Eh) and aggregate stability. As Eh decreased, aggregate stability decreased. The changes in redox‐sensitive elements (Mn and Fe), alkaline metals (Ca, Mg, and K), and DOC under reducing conditions were found to also contribute to decreased aggregate stability. The aggregate stabilities of cultivated soils were more sensitive to reducing conditions than those of uncultivated ones. The decrease in aggregate stability reached up to 21% in the cultivated soils and might be irreversible under field conditions. Short‐term reducing conditions may have detrimental effects on soil structure and water quality due to changes in soil aggregation and the chemistry of the soil solution.

Response of soil quality indicators and their spatial variability to land degradation in central Iran

Studying land degradation through a soil quality approach, which reveals soil functioning within the ecosystem, is necessary for sustainable management of land resources. This investigation was conducted to understand the changes of soil functions, resulting from exploitive management, using some soil quality indicators and their statistical and geostatistical measures. Undisturbed and disturbed sites were identified in each of two study areas, including an oak forest and a semiarid rangeland in central Iran. Soil organic carbon (OC), total nitrogen (TN), microbial respiration (MR), aggregate stability (AS), and hydraulic properties of the sites were determined. Statistical comparisons of frequency distribution functions of OC and MR revealed that these functions are normal in protected forest, while in the disturbed forest distributions deviate from normality. In the rangeland sites, the results were exactly the opposite. Spatial variability of the two variables in forest sites demonstrated pure nugget and spherical pattern in protected and disturbed sites, respectively. As for the rangeland ecosystem, pure nugget pattern was observed for both sites. According to our findings, protection of rangeland has resulted in higher OC and MR with no effect on the amount of TN and infiltration rate. The negative effect of this management system was a decrease in aggregate stability due to the formation of crust as a result of complete grazing exclusion. By contrast, improvement in all soil quality indicators in protected forest indicated the success of conservative management in this region.

Dairy Manure Effects on Soil Quality Properties and Carbon Sequestration in Alfalfa–Orchardgrass Systems

Dairy manure, as a passive by-product of livestock, is an important source of nutrients and organic matter to soils that support forage production. A split-plot experiment was conducted to determine the long-term (1994–1999) effects of dairy manure and chemical fertilizer on soil quality properties and carbon (C) sequestration in an alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.) forage systems. Five years after initiation of the experiment, soil core samples were collected randomly from between the alfalfa–orchardgrass rows under different treatments and analyzed or incubated to determine selected soil biological, chemical and physical properties. Results show that long-term application of dairy manure slurries significantly increased total organic, microbial biomass, potentially mineralizable, extractable and labile C pools, respectively, and improved soil aggregate stability by associated decrease in specific maintenance respiration rates, and subsequently enhanced soil quality. Relatively smaller amounts of total, microbial biomass, extractable and labile C pools with an increase in specific maintenance respiration rates, and increase in soil acidity accompanied by a decrease in aggregate stability suggest that long-term and continuous use of inorganic fertilizers for forage production did not improve soil quality or enhance C sequestration. The continuous cover of forage species, especially alfalfa, significantly improved soil quality over time as compared to orchardgrass species. The beneficial effects of organic amendments are important for proper disposal and utilization of dairy manures in forage production systems with an accompanied improvement in soil quality and C sequestration.

Evaluation of Microbial Activity in Soil Aggregate Stabilization and Degradation by the Use of Artificial Aggregates

AbstractA method for evaluating the mechanisms and factors involved in soil aggregate stabilization by microorganisms is introduced and data are presented to illustrate its use. This method involves the incubation of artificial soil aggregates of uniform and controlled physical and chemical properties, so that the effect of one or more variables of soil composition or environment on aggregate stability can be investigated.The stabilities of differently‐amended artificial aggregates of two diverse soil materials, incubated for up to 20 weeks, were determined by wet‐sieving the dried aggregates. The two soil materials, one obtained from the Ap horizon of a Kewaunee silty clay loam (Gray‐Brown Podzolic) and the other from the Al horizon of a Waupun silt loam (Brunizem), differed markedly in their contents of clay, nitrogen and organic carbon.Microbial gum‐amended Kewaunee aggregates possessed a higher initial stability and were more resistant to degradation with continued incubation than corresponding Waupun aggregates. Added nitrogen was associated with accelerated degradation of Kewaunee but not Waupun gum‐amended aggregates. Incubated sucrose‐amended Kewaunee aggregates showed a slower increase to maximum stability but retained stability longer than sucrose + nitrogen‐amended Kewaunee and sucrose‐ and sucrose + nitrogen‐amended Waupun aggregates. Nonamended and nitrogen‐amended aggregates of both soils were completely unstable throughout the incubation period. The stability of moist aggregates was a function of wetting rate and moisture status prior to sieving; aggregates moistened slowly to saturation were 100% stable to wet‐sieving.Periodate treatment of the aggregates indicated that, with the exception of incubated sucrose‐amended Waupun aggregates, “periodate‐oxidizable” polysaccharides were important in aggregate stabilization.Four days of incubation under highly aerobic or anaerobic conditions caused a rapid increase in the stability of sucrose‐amended Waupun aggregates. Continued aerobic incubation resulted in a rapid decrease in aggregate stability; aerobically incubated aggregates were totally unstable after 12 days. In contrast, continued anaerobic incubation was associated with an increase in stability; 100% aggregate stability was reached after 15 days and was still present after 4 weeks. Anaerobically‐stabilized aggregates lost their stability completely after 9 days of aerobic incubation.