Soil Aggregation Research Papers - Academia.edu (original) (raw)

2025, AIMS environmental science

Soil organic C (SOC) storage results when organic matter inputs to soil exceed losses through decomposition, and is strongly influenced by organic matter effects on soil aggregation. We evaluated the initial effects of lipid-extracted algae (LEA), a byproduct of biofuel production, on soil aggregate formation and SOC storage. In situ field incubations were conducted by amending soil with (1) 1.5% LEA, (2) 3.0% LEA, (3) 1.5% LEA + 1.5% wheat straw (WS) and (4) soil plus inorganic N (140 kg ha -1 NH 4 NO 3 ) and P [112 kg ha -1 Ca(H 2 PO 4 ) 2 •H 2 O] as the control. Soil samples were collected 0, 3, 6, 9, and 12 months after treatment application at 0-5, 5-15, and 15-30 cm. Soil was separated into macroaggregate (>250 µm), microaggregate (250-53 µm), and silt and clay (<53 µm) fractions by dry-sieving, and mean weight diameter was calculated. Soils and soil fractions were analyzed to determine C concentrations and associated δ 13 C values. Mean weight diameter 12 months after 3.0% LEA application was greater than the 1.5% LEA + 1.5% WS addition at the 5-15 cm depth. Soil amended with 1.5% LEA, 3.0% LEA or 1.5% LEA + 1.5% WS resulted in greater SOC after 12 months for all soil size fractions and depths. δ 13 C indicated that most LEA-C was initially associated with the silt and clay fraction, but later became more strongly associated with the macro-and microaggregate fractions after 12 months. Soil application of LEA enhanced initial aggregate formation and SOC storage by increasing aggregate MWD and macro-and microaggregate associated SOC over time. As the world population grows and resources become more limited, use of alternative energy sources, soil conservation, and environmental protection must be top research priorities. Our research emphasized all three and demonstrated that LEA can enhance soil structure and C storage.

2025, Frontiers in plant science

Root exudation contributes to soil carbon allocation and also to microbial C and energy supply, which subsequently impacts soil aggregation around roots. Biologically-driven soil structural formation is an important driver of soil fertility. Plant genetic determinants of exudation and more generally of factors promoting rhizosphere soil aggregation are largely unknown. Here, we characterized rhizosphere aggregation in a panel of 86 pearl millet inbred lines using a ratio of root-adhering soil dry mass per root tissue dry mass (RAS/RT). This ratio showed significant variations between lines, with a roughly 2-fold amplitude between lowest and highest average values. For 9 lines with contrasting aggregation properties, we then compared the bacterial diversity and composition in root-adhering soil. Bacterial α-diversity metrics increased with the "RAS/RT ratio." Regarding taxonomic composition, the Rhizobiales were stimulated in lines showing high aggregation level whereas Bac...

2025, Frontiers in Earth Science

Tropical ecosystems have an important role in global change scenarios, in part because they serve as a large terrestrial carbon pool. Carbon protection is mediated by soil aggregation processes, whereby biotic and abiotic factors influence the formation and stability of aggregates. Nutrient additions may affect soil structure indirectly by simultaneous shifts in biotic factors, mainly roots, and fungal hyphae, but also via impacts on abiotic soil properties. Here, we tested the hypothesis that soil aggregation will be affected by nutrient additions primarily via changes in arbuscular mycorrhizal fungal (AMF) hyphae and root length in a pristine tropical forest system. Therefore, the percentage of water-stable macroaggregates (> 250 µm) (WSA) and the soil mean weight diameter (MWD) was analyzed, as well as nutrient contents, pH, root length, and AMF abundance. Phosphorus additions significantly increased the amount of WSA, which was consistent across two different sampling times. Despite a positive effect of phosphorus additions on extra-radical AMF biomass, no relationship between WSA and extra-radical AMF nor roots was revealed by regression analyses, contrary to the proposed hypothesis. These findings emphasize the importance of analyzing soil structure in understudied tropical systems, since it might be affected by increasing nutrient deposition expected in the future.

2025, International Journal of Agricultural and Biosystems Engineering

A Field experiment was carried out to evaluate the effects of some bacterial fertilizers on some parameters growth and yield of two cultivars of watermelon during the season 2018-2019. The study included two factors the first factor was two cultivars of watermelon (Top yield and Charleston Gray) the second factor was bacterial fertilizer {control, Azospirillium barsilense (B1), Azotobacter chrococum (B2), Azospirillium barsilens+fluorescens Pseudomona (B3), Azotobacter chrococum+fluorescens Pseudomona (B4) and B1+B2+Pseudomona fluorescens (B5)}. Minimum days for germination were obtained from B4 (Azotobacter chrococum+fluorescens Pseudomona)+genotype Top yield (4.83 days). The highest percentage of phosphorus, potassium and iron was obtained in B5 treatment with combination bacterial fertilizer with cultivar of Top Yield (0.394%, 3.443% and 377.1mg matter dry-1 respectively). The maximum percentage TSS was observed in B5 treatment with Top Yield (10%). The best significant effect on yield production was obtained in B5 treatment with cultivar of Top Yield (134.93 ton per hector) compared to control treatment with cultivar of Charleston Gray (66.67 ton per hector).

2025, Agriculture, Ecosystems & Environment

It is widely believed that tropical soils (mainly Oxisols) have excellent physical characteristics such as high infiltration rates, high permeability of water, good and stable soil structure and that consequently, they can support mechanized agriculture. However in the Eastern Plains (Llanos Orientales) of Colombia, when Oxisols are subjected to tillage using disc harrow, soil physical conditions deteriorate rapidly. We report here that change in land use with deep-rooted tropical pastures can enhance soil quality by improving the size and stability of soil aggregates when compared with soils under monocropping. In addition, rates of water infiltration improved by 5 to 10-fold while rainfall acceptance capacity improved by 3 to 5-fold. We suggest that intensive and sustainable use of these Oxisols, could only be possible if an "arable" or "productive layer" (i.e. a layer with improved soil physical, chemical and biological properties) is constructed and maintained. One option to achieve this arable layer is through the use of introduced tropical pastures with deep rooting abilities that can result in increased soil organic matter and associated improvements in soil physical, chemical and biological properties. One land use option that can achieve these soil improvements is agropastoralism whereby pastures and crops are grown in short-term rotations.

2025

Land use change in moist tropical regions can significantly affect soil stability and carbon stocks, particularly with the conversion from primary forests. This study investigated the effects of land-use on soil aggregation and associated carbon stocks. A total of 200 soil samples were collected across five land-use, comprising rubber (RP) and oil palm plantations (OPP), bamboo forests (BF), fallow land (FL), and natural forest (NF). A comprehensive land-use intensity index, encompassing six key dimensions of land-use change, was integrated into robust regression models. The soil analyses revealed that macroaggregates dominated the top 15 cm (51-64 %), followed by meso-(30-39 %) and microaggregates (6-12 %). At deeper depths (15-30 cm), mesoaggregates prevailed (45.3-52.1 %). NF and BF exhibited the highest microaggregate fractions, resulting in lower mean weight diameter (MWD) and potentially lower aggregate stability. In contrast, RP and OPP displayed the highest macroaggregate distribution and MWD. Soil organic carbon generally decreased with land-use change from NF to FL and plantations, except for RP. MWD significantly correlated with silt and clay content, while meso-and micro-aggregates correlated with silt/clay content, MWD, and nitrogen (N). Models revealed that land-use intensity, bulk density, porosity, and N significantly influenced soil aggregate size. Notably, land-use intensity was lower in NF, BF, and FL compared to plantations (RP and OPP). The findings highlight the critical impact of landuse change in moist tropical regions on soil aggregation and carbon stocks, crucial for assessing the environmental consequences of converting natural forests to agricultural plantations. The study advances knowledge by introducing a comprehensive land-use intensity index, providing insights for sustainable land management and climate action. However, the findings are region-specific, and long-term experimentation and monitoring are needed to fully understand the effects of land use change on soil.

2025, Hydrological Processes

Soil surface crusting, a common phenomenon on cultivated soils, has major implications for agriculture and the environment because of its eects on soil hydrological properties, erosion and crop establishment. The objectives of this study were to evaluate land use controls on crust formation and the hydraulic response of soils to crust development for a Patancheru series soil (clayey skeletal, mixed, isohyperthermic Udic Rhodustalf) in south-central India. Soil aggregates, obtained from cultivated (PL) and naturally vegetated fallow (NV) land, were packed into sample trays and subjected to laboratory rain simulation to form crusts. Thin sections and visual observation indicated that crust development reached a more advanced stage in the PL case compared with NV following 90 min of rain at 40±80 mm h 71 intensity. This was re¯ected in a thicker crust layer with fewer voids in the former and a less smooth surface with partially disintegrated aggregates in the latter. The hydraulic response of the soil surface with the progression of crust development indicated a more permeable and less dense crust formed on NV than on PL soil. The results suggested that NV soil aggregates were more stable and that crust formation is more gradual for stable aggregates compared with the less stable PL aggregates. A structural crust-type formed on the Patancheru soil by means of parallel subprocesses involving translocation and illuviation of aggregate disruption by products, and raindrop compaction and particle rearrangement.

2025, Mitigation and Adaptation Strategies for Global Change

Drylands are very susceptible to the effects of climate change due to water stress. One possible climate change adaptation measure is the construction of lakes to increase water availability for drinking and irrigation (food production) and decrease fire risk. These lakes can also increase local biodiversity and human well-being. However, other non-target services such as carbon (C) storage, water purification, and sediment retention might also change. Our main aim was to evaluate the trade-offs on non-targeted ecosystem services due to lakes construction in drylands. This was done using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) modeling tools, comparing a Mediterranean area located in southwest (SW) Europe, with and without artificial lakes. Results showed that the construction of artificial lakes caused an increase of 9.4% in C storage. However, the consequent increase in agricultural area decreased water purification and sediment retention services. This could diminish the life span of the lakes changing the initial beneficial cost-benefit analysis on lakes as adaptation measures to climate change. As a global measure for mitigation and adaptation to climate change strategy, we consider lake construction in drylands to be positive since it can store C in sediments and reduces the vulnerability to water scarcity. However, as a general recommendation and when built to support or increase agriculture in semi-arid landscapes, we consider that lakes should be complemented with additional measures to reduce soil erosion and nutrient leaching such as (i) locate agricultural areas outside the lakes water basin, (ii) afforestation surrounding the lakes, and (iii) adopt the best local agriculture practices to prevent and control soil erosion and nutrient leaching.

2025, Geoderma

No-tillage (NT) and legume cover crops generally improve the quality of tropical and subtropical soils, but the mechanisms underlying these effects are not well known. We performed a study to investigate the influence of NT and legume cover cropping on microbial cell-wall constituents [glucosamine (GlcN), taken as indicator of fungal cell-wall; muramic acid (MurN), taken as indicator of bacterial cell-wall], and on their relationships with soil aggregation and soil organic carbon (SOC) accumulation in different fractions (light fraction, and sand-, siltand clay-sized fractions) of a subtropical Acrisol in Southern Brazil. The GlcN concentration ranged from 450.5 mg kg -1 in the 0-5 cm soil layer to 20.5 in the 75-100 cm soil layer, approximately 10 times greater than MurN concentrations (53.1-2.7 mg kg -1 for the same soil layers). No-tillage and legume cover crops favoured the accumulation of fungal and bacterial cell-wall constituents in whole soil, especially in the top 5 cm, with a preferential enrichment in GlcN. Legume cover cropping and NT resulted in greater accumulation of C in the light fraction in surface soil, which favoured the fungal community that, in turn, mediated an improvement in soil aggregation. Fungal-derived glucosamine also preferentially accumulated down to 100 cm depth, and more specifically in the clay-sized fraction of soil, suggesting a specific role of fungi in SOC accumulation at depth. Overall, our study provides field-based evidence that the accrual of fungal cell-wall constituents under NT and legume cover cropping is a key process leading to aggregation and SOC accumulation in subtropical soil profiles. Recent models of SOC formation now consider microbial residues as a main source for stable soil organic matter . Moreover, SOC stabilization by mineral-organic association and soil aggregation would be favoured by labile C inputs . More field-based observations are needed to support these concepts. Cell-wall constituents of fungi and bacteria in soil can provide a "fingerprint" for SOC formation . Contents of muramic acid (MurN) and glucosamine (GlcN) have been used to distinguish bacterial and fungal cell wall residues, respectively, mainly in temperate environments (e.g. . Few studies have been performed in subtropical or tropical soils. In these studies, greater amounts of total amino-sugars,

2025, Legume Research, Volume 48 Issue 4 (April 2025)

Background: In the century we live in, due to the environmental problems caused by the use of synthetic fertilizers, sustainable solutions are being sought. The use of beneficial microorganisms as biological fertilizers, which are directed in line with these searches, is remarkable. has become a phenomenon. This study aimed to investigate the effect of microbial fertilizer comparing them with synthetic fertilizer in Van ecological conditions. Methods: This research was conducted in summer seasons of 2020 and 2022 to investigate the effects of microbial (Bacillus atrophaeus, Bacillus-GC group and Rhizobium gallicum) and chemical (Control: No fertilizer, NP100: 40 kg N/ha-1 , 60 kg/ha-1 P 2 O 5 and NP50: 20 kg N/ha-1 , 30 kg/ ha-1 P 2 O 5) fertilizer applications on the yield and nutrient content of beans. The experiment was conducted in split plot design and replicated thrice. Result: Experimental results revealed that the use of microbial fertilizers led to a significant improvement in the morphological characteristics of bean plants in comparison to those treated with inorganic fertilizers. Besides, the utilization of microbial fertilizers, particularly when arranged in a consortium, exhibited performance that was nearly indistinguishable from that of synthetic fertilization. The highest grain yield was obtained with NP100 (40 kg N/ha-1 , 60 kg/ ha-1 P 2 O 5) + NR (Bacillus atrophaeus + Rhizobium gallicum) application. Apart from this effect, other microbial applications also played a positive role in plant growth and production. It was therefore concluded that microbial fertilizers can be employed as a suitable alternative to chemical fertilizers in order to establish a sustainable agricultural system in bean cultivation, to enhance productivity, to safeguard and to improve soil properties.

2025, European Journal of Soil Biology

This study examines the role of abiotic (texture, calcium carbonates or iron) and biotic parameters (earthworm and enchytraeid activities) on the initial phases of soil aggregation. Our research focused on humus forms in alluvial soils, which are considered as young and heterogeneous environments. We hypothesized that the soil structure formation is determined by both the nature of the recent alluvial deposits and the soil fauna. For this purpose, six sites were chosen throughout two types of softwood forests (willow and alder forest) representing two stages of vegetation succession. Evidence of soil texture influence on aggregate stability was observed. A dominance of a coarse sand fraction caused a quick colonization of enchytraeids and epigeic earthworms while a silty texture favoured the presence of anecic earthworms, thus increasing the aggregate stabilisation. Iron forms, acting as cementing agents, were observed in the coarse silt, while calcium carbonates were equally distributed among the textural fractions. Active calcium carbonate fraction, binding organic matter with mineral components, was not found in the coarse sand fraction. In conclusion, the tree age cannot alone be used as an indicator of the humus form evolution but biological and physicochemical parameters also influence the initial steps of soil structuration.

2025, Agricultural Engineering International: The CIGR Journal

The knowledge of soil hydraulic properties and processes leads to better predictions of both agricultural and environment impact. The objectives of this research are to determine, predict and compare the relationship between measured and estimated soil hydraulic properties and also spatially characterize these properties using geostatistics. Mini disc infiltrometer at a suction rate of 2 cm per second was used for the determination of soil hydraulic properties at different points of an alfisol in Nigeria. Soil samples (100, 200 and 300 mm depths) were also analyzed to determine soil bulk density (BD), total porosity (PT) and water holding capacity (WHC). The coefficients of variation (CV) of the textural classes indicate a non-considerable variability of the sand (CV=6%), silt (CV=20%) and clay (CV=3%) contents. From the statistical and spatial analysis for the different parameters, the variability of hydraulic conductivity (48%>33%>31%), cumulative infiltration (40%>26%&gt...

2025

An evaluation of geometrical pore parameters as influenced by rock weathering is helpful in understanding the development of soil. The objective of this study was to investigate three-dimensional (3-D) geometrical pore characteristics in rocks as affected by the degree of weathering. Rock fragments (clasts) from several moraines, ranging in age from 15-ky to 160-ky, were scanned using high-resolution X-ray computed tomography (CT) at 39-42 µm resolution. From each sample a 480×480×580 data block were extracted for analysis with 3-Dimensional Medial Axis Rock (3DMA-Rock) computer software. As weathering increased, samples developed more pores, and these pores were more extensively connected to other pores. Highly weathered samples had pores with the highest coordination numbers and characteristic coordination number constants. These parameters were significantly different from the un-weathered or partially weathered samples. More weathering also resulted in longer path lengths (PLs) and larger path length constants. PLs were < 2 mm for the un-weathered samples while partial and more fully weathered samples had values ranging up to 6 mm. The average tortuosity values decreased from 2.34 to 1.30 with weathering. Results indicated that 3-dimensional analysis of pore geometry can be used to discriminate rock weathering as well as to better understand the spatial variations in pore parameters.

2025

A field experiment was carried out on sugarcane plant-ratoon system to develop nutrient management strategies for sustaining soil health, quality and sugarcane production at Research Farm, Dr. Rajendra Prasad Central Agricultural University, Pusa, Bihar. Trials were conducted to test the efficiency of various fertilizers in sugarcane on solubility of applied inorganic fertilizer during spring season in calcareous soil. The pooled data revealed that number of millable cane (NMC), cane and sugar yield varied significantly due to integrated use of organic and inorganic fertilizer with bio-fertilizer in combination both in plant and ratoon crops. The significant increase in NMC, cane and sugar yield was recorded in the treatments receiving organic and inorganic fertilizer in combination with bio-fertilizer over control. The highest number of NMC (103.0 × 10 3 ha-1), cane yield (85.8 t ha-1) and sugar yield (11.21 t ha-1) was recorded in treatment T9 i.e 75% NPK of RDF + Acetobacter

2025

Soil health refers to the ecological equilibrium and the functionality of a soil and its capacity to maintain a well balanced ecosystem with high biodiversity above and below surface, and productivity. However, feeding seven billion people with environmental sustainability is a challenge for the next generations. Good soil physical health is essential for optimum sustained crop production. Soil tillage has a direct influence on the soil physical health. Tillage exerts impact on the soil purposely to produce crop and consequently affects the environment. An appropriate tillage system needs to be practiced so as to take care of the soil health, plant growth and the environment simultaneously. Therefore, to achieve sustainable food production with minimal impact on the soil and the atmosphere, conservation tillage practices become more important now than ever ensuring sustainable food production and maintaining environmental integrity. This paper aims to review the work done on maintai...

2025

The dynamics of soil structure is driven by hydraulic and mechanical stresses. Hydraulic stress causes soil swelling and shrinkage during natural wetting and drying. Mechanical load results in soil compaction. In this paper we combined the hydraulic and mechanical stresses by considering shrinkage, moisture release and compaction concurrently. The volume of rigid pores compacted by mechanical stress do not alter soil pore shrinkage capacity. Their shrinkage curves are parallel to each other with an identical coefficient of linear extensibility (COLE) and shrinkage slope, although their structural shrinkage phases narrow with an increase in compaction stress. With different shrinkage properties of rigid and non-rigid pores, we proposed numerical methods to illustrate the bundle of the e-ϑ-σ relationship as affected by mechanical stress stemming from tillage management, and to model the loaded soil shrinkage behavior. The similarity of soil shrinkage behavior before and after tillage management can be easily assessed regarding the dynamics of soil structure during natural wetting and drying cycles.

2025

Abstract: There are two types of mycorrhizae: ectomycorrhizae and endomycorrhizae. Ectomycorrhizae form an extensive dense sheath around the roots, called a mantle. Hyphae from the fungi extend from the mantle into the soil, which increases the surface area for water and mineral absorption. This type of mycorrhizae is found in forest trees, especially conifers, birches, and oaks. Endomycorrhizae, also called arbuscular mycorrhizae, do not form a dense sheath over the root. Instead, the fungal mycelium is embedded within the root tissue. Endomycorrhizae are found in the roots of more than 80 percent of terrestrial plants We concluded that The relationship between plants and fungi is symbiotic because the plant obtains phosphate and other minerals through the fungus, while the fungus obtains sugars from the plant root. The long extensions of the fungus, called hyphae, help increase the surface area of the plant root system so that it can extend beyond the area of nutrient depletion. E...

2025

Grassland grazing, driven human activities, represents a prevalent form of land use conversion. While numerous studies have examined the impact of such conversions on soil carbon cycling, they primarily focus on the content and storage of soil organic carbon (SOC). However, research on the turnover dynamics of SOC and the underlying mechanisms triggered by land use conversions remains relatively scarce. In this study, radiocarbon ( 14 C) tracing technology was applied to investigate the effects of grassland grazing on SOC turnover in the Saihanba area of Hebei province, China. The results revealed that the turnover time of SOC in pasture grassland was shortened by approximately 250 years compared to meadow grassland, suggesting that grazing diminishes the ability of topsoil to stabilize SOC. Furthermore, our findings indicate that grazing leads to a decrease in soil CO 2 flux by 0.50 g C m -2 y -1 under aggregates larger than 250 μm and those between 63 and 250 μm. Conversely, the CO 2 flux under aggregates, specifically those between 2 and 63 μm and less than 2 μm, increased by 0.96 g C m -2 y -1 . This shift suggests a significant increase in the contribution of older SOC pools to the overall soil CO 2 flux. Our study provides novel insights into SOC cycling in the context of grassland grazing, highlighting the importance of understanding SOC turnover dynamics for effective land management.

2025, Frontiers in plant science

2025

Abstract. The Georgia P Index was developed as a tool to evaluate the risk of bioavailable P loss in fields under various management practices. We compared the results of the P Index with four years of data from 1.5 m by 4.6 m... more

2025, Soil and Tillage Research

In the Fraser River Delta of British Columbia, Canada, one in three farms faces soil problems associated with poor structure and low organic matter content. Surface soil structure usually degrades in early spring due to prolong wet conditions and a lack of surface cover during winter. Rates of change of surface soil aggregation under different overwinter cover crops followed by spring tillage operations were studied on a lowland soil in the Fraser River. Cover cropping treatments were bare control, winter-killed spring barley (Hordeurn vulgare L.) (cv. Virden), fall rye (Secale cereale L.) (cv. Danko) and annual ryegrass (Lo&m multiflorurn Lam.) (cv. Westerwolds). Aggregate stability, expressed as mean weight diameter (MWD) and the 2-6 mm aggregate-size fraction, decreased from fall to spring, then increased again over summer months. This seasonal variation in MWD was much more pronounced in the least stable bare soil than in the more stable cover cropped soils. In spring, overwinter cover crops had significantly higher MWD and the proportion of 2-6 mm water-stable aggregates up to 0.75 mm and 0.27 kg kg-i, respectively, when compared to bare control soil. Improved aggregate stability with cover crops was related to increasing organic carbon in the soil. After the plots were cultivated in spring, winter cropped soils had lower proportion of > 6 mm clods up to 0.28 kg kg-' than did soils left bare over winter. On the other hand, tilled plots had higher MWD and 2-6 mm aggregates for all cover cropping treatments due to lower aggregate water content at sampling, when compared to no-tilled plots. Overall, the greatest improvement in aggregate stability was observed under annual ryegrass, followed by fall rye and winter-killed spring barley. The results suggest that winter cover crops, such as annual ryegrass, may protect aggregate breakdown during winter and result in better structure after spring tillage operations when compared to the bare soil. 0 1997 Elsevier Science B.V.

2025, Soil Science Society of America Journal

Because plant absorption of P depends on the desorption of P around soil aggregates Linquist et from soil, understanding P desorption from soils may improve the precision of P diagnosis and fertilization recommendations. Many al., 1997), suggesting that larger soil aggregates with soils with high P retention due to high levels of Fe and Al are also relatively less surface area than small aggregates may highly aggregated. Extractable P is sometimes higher on larger size reduce P fixation and result in increased availability of aggregates, which will probably result in increased P release from recently applied P. With equivalent levels of extractable aggregates. The effects of aggregate size on P availability of three P, one might expect that desorption from larger aggrehighly weathered soils were quantified with a column-leaching study gates may be lower if P diffuses deeply into the agand a pot experiment. Phosphorus desorption by leaching from small gregates. aggregates was greater than that from large aggregates when P had Soil P release may affect both P supply to plants and been added to the bulk soil (Kapaa and Leilehua soils) and a mixture P discharge from watersheds. Desorption of P would, of different-sized aggregates (Leilehua soil). When aggregates were therefore, probably be more pertinent than P sorption separated and then P added, however, P desorption was greater from large aggregates (4-6 mm) than from small aggregates (Ͻ0.5 mm). when evaluating plant-available P and P buffering prop- erties of soil, an observation noted many years ago by expanded Elovich equations suggests that P desorption is probably . Several experimental techcontrolled by diffusion processes. A pot experiment showed that total niques have been used to investigate P desorption. These include extraction of soil P with P-free solution shoots, and the root dry weights of plants grown in the large aggregates (Kafkafi et al., 1967;, addition of materi-(2-6 mm) were higher than for plants grown in the small aggregates als with high capacities to bind P in order to deplete P (Ͻ0.5 mm) after equal amounts of P were added to the separated in soils , and aggregate fractions. Increased P uptake with increased aggregate size leaching of soil columns with P-free solutions (Sawhney, was attributed to increased P release from aggregates because of 1977; van der Zee and Gjaltema, 1992). The soil column reduced P fixation. The results suggest that soil management that favors soil aggregation may, in some cases, increase availability of leaching method was used in our experiments because applied P. Perhaps the distribution of soil aggregates should be consid-it prevented the breakup of soil aggregates resulting ered in making P management decisions.

2025

La geometría fractal permite describir teóricamente estructuras de diversa naturaleza. De esta se obtiene, la dimensión fractal de fragmentación (D), la cual, está relacionada con el particionamiento y escalamiento que presentan las mismas, y que ha sido empleada en la caracterización y estudio de distribución de tamaño de partículas del suelo (DTP). Se planteó aplicar el modelo fractal e investigar sobre el proceso de microestructuración en seis suelos agrícolas de la pradera pampeana con DTP contrastantes. Las DTP y las D se obtuvieron bajo dos pretratamientos, uno sin materia orgánica (SMO), máxima dispersión, y otro con materia orgánica (CMO) conservando así la microestructura. El modelo fractal aplicado a la DTP con el pretratamiento SMO, en los suelos franco limosos, alcanzó a describir en promedio el 98% de la masa analizada; en el suelo franco arenoso ajustó hasta los 50 µm, describiendo el 38% de la masa, mientas que el suelo areno franco no ajustó al modelo fractal. Con lo...

2025, Ciencia Del Suelo

Investigador del CONICET.

2025, Soil Science Society of America Journal

size and density are identified as two of the most impor- tant properties of soil aggregates. Aggregate density is DENSITY BY VOLUME DISPLACEMENT used to estimate inter-aggregate porosity, and, together with aggregate size, influence plant growth (De Freitas IN TWO NON-MIXING LIQUIDS et al., 1996). During the last decade, fractal models of soil structure have been developed that use variations in Guillermo O. Sarli, Roberto R. Filgueira, and Daniel Gime ´nez* aggregate density with aggregate size as a fundamental scaling property related to soil water retention and other Abstract soil properties (Rieu and Sposito, 1991). There is an interest in methods to determine density of soil aggre-Soil aggregate density is an important property influencing soil gates, and several methods have been proposed. biological, chemical, and physical processes. Current methods used Some methods use a group of aggregates to determine to estimate soil aggregate density are based on more or less restrictive assumptions or require specialized equipment. This study was con-an average aggregate density. In this group is the method ducted to develop an alternative method for measuring aggregate proposed by Chepil (1950), which was successfully used density of soil and other porous objects that is both simple and theoretto determine the density of aggregate size fractions sepaically sound. The proposed method solves the balance of forces rerated by sieving dry soil (Eghball et al., 1993; Filgueira sulting when a kerosene-saturated aggregate is immersed in a mix of et al., 1999a, 1999b). The method, however, assumes water and glycerin. We tested the accuracy of the method by measuring that aggregates and sand grains of similar size pack in the volume of 40 aggregates with diameters ranging from 4 to 20 mm the same way. This assumption is likely to introduce and with variable densities. Soil aggregates were saturated in kerosene, error in the determination of the density of irregularlydrained at a tension of Ϫ30 mm, and their volume estimated using a shaped aggregates. Voorhees et al. (1966) circumvented pycnometer. Upon resaturation, aggregates were suspended from a this problem by using a mixture of glass beads and thread and successively weighed in air, in kerosene, and in a mix of water and glycerin. Aggregate volumes and densities varied between aggregates packed to a known volume to determine 1.20 ϫ 10 Ϫ7 and 3.85 ϫ 10 Ϫ6 m 3 and between 1.05 to 1.86 Mg m Ϫ3 , reaggregate density. The same principle was applied by spectively. On average, aggregate volumes estimated with the pycno-

2025

Phosphorous is an essential nutrient in plants required for root establishment. In the soil, it is applied as DAP, TSP or phosphate rocks. In acid soils, aluminium and iron are dominant and tend to “fix” phosphorous, making it unavailable for plant uptake. Phosphorous deficiencies are monitored through soil chemical analysis. There are many methods for the extraction of available forms; however the choice is dependent on several factors among them soil pH. Forty soil samples were collected from three different acid soils in Western Kenya. The samples were air dried, sieved under 2.0 mm sieve and stored in sample bags for subsequent analysis. Phosphorous extraction of was carried out using a basic extractant (Olsen bicarbonate method) and acid extractant (double acid method). The extracts were measured colorimetricaly by the ascorbic acid method at 880 nm wavelength. The methods were compared in terms of extracting efficiency, correlations and soil critical levels. The soils had a pH...

2025, Plant and Soil

A five-year monitoring study has been carried out to examine the combined effects of grazing and atmospheric nitrogen deposition on water and solute fluxes in dry coastal dune grasslands. Two vegetation types were studied: (a) a short, species-rich stand on calcareous sand (foredune site) and (b) a short, species-poor stand on partly decalcified soil on calcareous sand (innerdune site). In

2025, European geosciences union general assembly

Microbial soil communities play a fundamental role in soil organic matter mineralization, which is a key process for plant nutrition, growth and production in agro-ecosystems. A number of these microbial processes take place in the rhizosphere: the soil zone influenced by plant roots activity, which is a "hotspot " of biological and physico-chemical activity, transfers and biomass production. The knowledge of rhizosphere processes is however still scanty, especially regarding the interactions between physico-chemical processes occurring there and soil microorganisms. The rhizosphere is a place where soil aggregates are more stable, and where bulk density, porosity, water and nutrients transfer are modified with respect to the bulk soil (e.g. because of production of mucilage, of which exo-polysaccharides (EPS) produced by roots and microorganisms. During a maize field experiment, rhizospheric soil (i.e. soil strongly adhering to maize roots) and bulk soil were sampled twic...

2025, Biology and Fertility of Soils

Production of exopolysaccharides (EPS) can be used as a criteria for the isolation of stress tolerant microorganisms. In the present study, EPS-producing fluorescent pseudomonads were isolated from alfisols, vertisols, inseptisols, oxisols, and aridisols of different semiarid millet growing regions of India and were screened in vitro for drought tolerance in trypticase soy broth supplemented with different concentrations of polyethylene glycol (PEG6000). Out of the total 81 isolates, 26 could tolerate maximum level of stress (-0.73 MPa) and were monitored for the amount of EPS produced under maximum level of water stress. The strain GAP-P45, isolated from alfisol of sunflower rhizosphere, showed the highest level of EPS production under water stress conditions, was identified as Pseudomonas putida on the basis of 16S rDNA sequence analysis, and was used as seed treatment to study its effect in alleviating drought stress effects in sunflower seedlings. Inoculation of Pseudomonas sp. strain GAP-P45 increased the survival, plant biomass, and root adhering soil/root tissue ratio of sunflower seedlings subjected to drought stress. The inoculated bacteria could efficiently colonize the root adhering soil and rhizoplane and increase the percentage of stable soil aggregates. Scanning electron microscope studies showed the formation of biofilm of inoculated bacteria on the root surface and this, along with a better soil structure, might have protected the plants from the water stress.

2025, Universidade Federal do Rio de Janeiro

Primeiramente agradeço a minha família: meu pai, por ter me mostrado a geologia, ciência à qual eu não conhecia nos idos de 2004, pela paciência e muito mais; minha mãe, pelo carinho, dedicação e por ser minha base e meu irmão, maior companheiro da minha vida. Agradeço especialmente minhas orientadoras, Prof.ª Dr.ª Helena Polivanov e Prof.ª Drª Andrea Borges pelo projeto e pela ajuda na execução do mesmo. A Prof.ª Dr.ª Helena Polivanov agradeço ainda pelos três anos de estágio, por ter tido paciência quando entrei "cru" no laboratório e por ter me dado força nesses anos. Agradeço ao Prof. Dr. Emílio Barroso pelas sugestões e ensinamentos e a Fátima Seabra e Osório Luiz por toda ajuda dada nos ensaios nos laboratórios de Solos e Via Úmida, respectivamente. Agradeço ao meu braço direito nesse projeto, Matheus Amaral, e pela colaboração de Mário e Kadson. Agradeço aos meus amigos, que me aturaram em toda a faculdade. Sem vocês, com certeza, a faculdade não teria graça alguma. Muito obrigado pelas descontrações, estudos e pelas tantas alegrias por qual passamos nesses cinco anos. Agradeço a Prof.ª Dr.ª Laura Maria Goretti da Motta por ter cedido seu laboratório, a Msc. Mariluce Ubaldo por toda atenção e sugestões dadas e todos os técnicos do Setor de Geotecnia da COPPE/UFRJ. Por fim, agradeço a minha amada Anna Claudia, pelo carinho, pela paciência e pela força que me encorajava a continuar.

2025

Soil disturbance from tillage is a major cause of organic matter depletion and reduction in the number and stability of soil aggregates when native ecosystems are converted to agriculture. No-till (NT) cropping systems usually exhibit increased aggregation and soil organic matter relative to conventional tillage (CT). However, the extent of soil organic matter changes in response to NT management varies between soils and the mechanisms of organic matter stabilization in NT systems are unclear. We evaluated a conceptual model which links the turnover of aggregates to soil organic matter dynamics in NT and CT systems; we argue that the rate of macroaggregate formation and degradation (i.e. aggregate turnover) is reduced under NT compared to CT and leads to a formation of stable microaggregates in which carbon is stabilized and sequestered in the long term. Therefore, the link between macroaggregate turnover, microaggregate formation, and C stabilization within microaggregates partly determines the observed soil organic matter increases under NT.

2025, Soil Science Society of America Journal

In semiarid agroecosystems of the Ebro valley (NE Spain) soils are characterized by low soil organic matter (SOM) and a weak structure. In this study we investigated the individual and combined effect of tillage system (no-tillage, NT; reduced tillage, RT; conventional tillage, CT) and cropping system (barley-fallow rotation, PN-BF and continuous barley, PN-BB) on soil organic carbon (SOC) storage as well as the physical protection of SOM fractions by soil aggregates in three long-term experimental sites. In both cropping systems, total SOC content was more than 30% higher in NT compared with CT in the 0-to 5-cm depth. The suppression of fallowing in the PN-BB cropping system led to a greater SOC stabilization only in NT. In all the three sites, greater proportion of water-stable macroaggregates (> 250 µm) was found under NT than under CT in the 0-to 5-cm depth. Macroaggregate organic C concentration (250-2000 µm) was greater in NT compared with CT in the BB cropping system, but did not differ with tillage treatment in the PN-BF rotation. Greater proportion of microaggregates within macroaggregates in NT compared with CT was only found in AG. However, greater C stabilized inside these microaggregates was observed in AG, SV and PN-BB in the 0-5 cm depth. The results of this study demonstrate that in the semiarid Mediterranean agroecosystems of the Ebro valley, the adoption of NT together with the suppression of long-fallowing period can significantly increase the amount of SOC stabilized in the soil surface and improve soil structure and aggregation.

2025, Soil Biology & Biochemistry

Physical protection of soil organic matter by aggregates is considered to be an important mechanism for soil carbon stabilization. In this study, we evaluated the effect of drying and wetting on the interrelationships between macroaggregate formation and degradation (i.e. macroaggregate turnover), microaggregate formation within macroaggregates, and aggregate-associated carbon dynamics. Dry±wet (DW) cycles were used to simulate one of the soil aggregate disruptive effects induced by tillage. A conceptual model developed from long-term no-till (NT) and conventional tilled (CT) ®eld experiments was then used to interpret our results. Sieved (250 mm) air-dried soil samples were taken from Weld silt loam soil (Aridic Paleustoll) that had been cultivated continuously. The samples were mixed with 13 C-labeled wheat and incubated for 74 days. One set of soil samples was subjected to four DW cycles, while the other set was kept at ®eld capacity (control). At days 14, 44 and 74, water-stable microaggregates (53±250 mm) held within large macroaggregates (.2000 mm) were isolated. Inter-and intra-microaggregate particulate organic matter (POM) fractions were separated and analyzed for total and wheat-derived C. After two DW cycles (day 44), we observed a signi®cantly lower proportion of water-stable microaggregates within DW macroaggregates compared to control macroaggregates (9 versus 13% of the macroaggregate weight). Simultaneously, DW macroaggregates had signi®cantly lower intramicroaggregate POM-C concentrations compared to control macroaggregates. This difference in intra-microaggregate POM-C between DW and control was more signi®cant for native intra-microaggregate POM-C (0.73 versus 1.03 g kg 21 macroaggregates) (P , 0.05) than for wheat-derived intra-microaggregate POM-C (41 versus 49 mg C kg 21 macroaggregates) (P , 0.1). After two DW cycles (day 44), drying and wetting no longer caused macroaggregate disruption. From day 44 to day 74, both the proportion of microaggregates and the concentration of intra-microaggregate POM-C signi®cantly increased in DW macroaggregates. We conclude that POM-C in new microaggregates within macroaggregates is inhibited by an enhanced macroaggregate turnover, which is only in the short term enhanced by drying and wetting. Furthermore, we suggest that besides a release of total (i.e. native and wheat-derived) POM upon macroaggregate breakdown, drying and wetting induced a fast reformation of macroaggregates with preferential incorporation of wheat-derived POM, resulting in a relative decline of native POM-C in DW macroaggregates.

2025, Soil Biology & Biochemistry

2025, Soil Science Society of America Journal

Tillage events have an important infl uence on residue incorporation into soil profi les and soil aggregate disruption, and ultimately infl uence the net C gain or loss in soils. Thus, our objective was to evaluate tillage-induced infl uences on aggregate structure, residue-derived C stabilization, and the subsequent effi ciency of C stabilization in aggregates of no-till (NT) and tillage management (TM) practices at different depth increments of the soil profi le. Uniformly 13 C-labeled wheat residues were added to incubation cores representing soils under NT and TM during a year-long in situ incubation at a dryland agriculture experiment site. Residue was added directly onto the surface of NT cores, while residues were incorporated into the 0-to 5-, 5-to 15-, and 15-to 30-cm depth increments of the TM cores. We found that residue additions did not have a signifi cant effect (P > 0.05) on aggregate dynamics in either NT or TM, but NT management did result in the greatest stabilization of residue-derived C (11.2 ± 2.4 g residue C kg -1 soil kg -1 residue C added, P < 0.05) in the macroaggregate (>250-µm) fraction of the 0-to 15-cm increment. Residue-derived C stabilization was signifi cantly greater (P < 0.05) in the 0-to 30-cm increment than in the 0-to 15-cm increment of the TM management cores. Overall, our results indicate that, within a plow depth of 15 cm, limiting the tillage-induced disruption of aggregates has a stronger infl uence on the effi ciency of C stabilization than residue incorporation into the profi le via tillage. When residues are distributed to a 30-cm depth, however, the negative impact of aggregate disruption through tillage appears counterbalanced, with similar effi ciencies of C stabilization between the NT and TM practices, possibly due to slower decomposition of residues deeper in the profi le.

2025, Agronomy Journal

a function of C inputs and losses (Campbell et al., 2000a(Campbell et al., , 2000b)). Inputs, primarily as photosynthates, are added Summer fallow (fallow) is still widely used on the North American either directly (e.g., crop residue) or indirectly (e.g., Great Plains to replenish soil moisture between crops. Our objective was to examine how fallowing affects soil organic carbon (SOC) in animal manure derived from plant C). Losses occur various agronomic and climate settings by reviewing long-term studies mostly as CO 2 from decomposition. Summer fallow rein the midwestern USA (five sites) and the Canadian prairies (17 duces C storage in several ways . sites). In most soils, SOC increased with cropping frequency though First, frequent summer fallow usually reduces inputs of not usually in a linear fashion. In the Canadian studies, SOC response photosynthetically derived C into soils because there to tillage and cropping frequency varied with climate-in semiarid are no plant C inputs (except via weeds) during the conditions, SOC gains under no-till were about 250 kg ha Ϫ1 yr Ϫ1 fallow phase. Second, it may enhance the rate of minergreater than for tilled systems regardless of cropping frequency; in alization of soil organic matter to CO 2 because it keeps subhumid environments, the advantage was about 50 kg ha Ϫ1 yr Ϫ1 for the soil wetter (and perhaps warmer) for longer periods. rotations with fallow but 250 kg ha Ϫ1 yr Ϫ1 with continuous cropping. Further, if tillage is used to control weeds during sum-Specific crops also influenced SOC: Replacing wheat (Triticum aestivum L.) with lentil (Lens culinaris Medikus) had little effect; replacing mer fallow, decomposition may be accelerated by diswheat with lower-yielding flax (Linum usitatismum L.) reduced SOC ruption of soil aggregates and exposure of organic matgains; and replacing wheat with erosion-preventing fall rye (Secale ter to microbial activity. Summer fallow may also cereale L.) increased SOC gains. In unfertilized systems, cropping accelerate soil C losses by erosion, but these losses are frequency did not affect SOC gains, but in fertilized systems, SOC localized, often resulting in redistribution of C more gains often increased with cropping frequency. In a Colorado study than in its release to the atmosphere (Gregorich et (three sites each with three slope positions), SOC gains increased al., 1998). with cropping frequency, but the response tended to be highest at Our objective was to review data from long-term exthe lowest potential evaporation site (where residue C inputs were periments in the U.S. and Canadian Great Plains to greatest) and least in the toeslope positions (despite their high residue determine the magnitude of the effect of summer fallow C inputs). The Century and the Campbell et al. SOC models satisfactorily simulated the relative responses of SOC although they underesti-on changes in SOC and to assess how these changes are mated gains by about one-third. modified by such factors as tillage, fertility, soil type, topography, and climate. C.A. Campbell and E.G. Gregorich, Agric. and Agri-Food Canada, time (e.g., the shift from wet digestion methods to the Cent. Exp. Farm,

2025, Biogeochemistry

Crop-based agriculture occupies 1.7 billion hectares, globally, with a soil C stock of about 170 Pg. Of the past anthropogenic CO2 additions to the atmosphere, about 50 Pg C came from the loss of soil organic matter (SOM) in cultivated soils. Improved management practices, however, can rebuild C stocks in agricultural soils and help mitigate CO2 emissions.Increasing soil C stocks requires increasing C inputs and/or reducing soil heterotrophic respiration. Management options that contribute to reduced soil respiration include reduced tillage practices (especially no-till) and increased cropping intensity. Physical disturbance associated with intensive soil tillage increases the turnover of soil aggregates and accelerates the decomposition of aggregate-associated SOM. No-till increases aggregate stability and promotes the formation of recalcitrant SOM fractions within stabilized micro- and macroaggregate structures. Experiments using13 C natural abundance show up to a two-fold increas...

2025, Soil Science Society of America Journal

2025, Soil Biology and Biochemistry

2025, Applied and Environmental Microbiology

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was applied to soils in microcosms, and degradation was monitored after each of five repeated additions. Total DNAs were isolated from soil bacterial communities after each 2,4-D treatment. The DNA samples were analyzed on slot blots and Southern blots by using a tfdA gene probe subcloned from plasmid pJP4 and a Spa probe derived from a different 2,4-D-degrading isolate, a Sphingomonas paucimobilis strain. 2,4-D applied to soil was quickly degraded by indigenous microbial populations. As determined by slot blot analyses of DNA from a Michigan soil, the increase in hybridization signal in response to 2,4-D treatments was greater with the Spa probe than with the tfdA probe. In contrast, the DNA from a Saskatchewan soil exhibited an increase in hybridization signal with the tfdA probe. This indicated that a population with 2,4-D-degradative gene sequences different from the tfdA gene sequence was dominant in the Michigan site, but no...

2025, Annals of Biological Research

The present study aims to analyze the interaction of prevailing biotic pressure on soil environment with emphasis on its physicochemical and microbiological characteristics determining fertility status of biogenic structures in comparison to soil. The experimental results revealed that the physico-chemical characteristics (viz., pH, C, N, P, K) of midden were higher in comparison to soil. Middens with high N mineralization potential tend to be inherently fertile. Bacterial population increased up to 21st day and there after declined sharply in both midden and soil samples with higher population in the former. Highest microbial count showed a positively significant correlation with enzyme activitiy in earthworm midden. The biogenic structure showed to be beneficial for soil.

2025, Biology and Fertility of Soils

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2025, Bioscience Journal

The current study aimed to evaluate the effects of different tillage systems on soil organic matter (SOM) contents and green corn yield (total ear weight) of an Argissolo Vermelho-Amarelo (Ultissol) in Coastal tablelands of northeast Brazil. The experiment was arranged as a strip plot design with three replications. Three tillage practices [conventional tillage (CT), minimum tillage (MT) and no-tillage (NT)] were laid out as a whole plot each (830 m²). Then, each plot was equally split into 12 experimental units (60 m²), distant 1 x 10 m from each other, where in four cover crops [pigeon pea (Cajanus cajan (L.) Millsp.), sunn hemp (Crotalaria juncea L.), beans (Phaseolus vulgaris) and peanut (Arachis hypogeae) were seedling previous to corn cultivation. Neither cover crops, nor tillage practices affected SOM contents at 0.20 m depth. An exception was observed on beans plots in which CT resulted on the lowest SOM content (8.5 dag kg -1 ) at 0-10 cm soil layer. Regarding green corn ears yield, CT adoption also resulted in lower weight (4.11 t ha -1 ) than those on NT (7.65 t ha -1 ), regardless of cover crop. On the other hand, the influence of cover crops on green corn yield relied upon tillage practices. Peanuts and sunn hemp performed best to improve corn yield in CT; peanuts and beans increased by 14 % the green corn ears yield in MT, while sunn hemp resulted in the highest total ear weight (9.42 t ha -1 ). Linear correlation of Pearson was significant for SOM and productivity green maize ears in minimum tillage beans (p <0.001; r = 0.996). After four years of absence or reduced soil disturbance, there was no increase in SOM levels. The plowing appears to be important for increasing the entry of C soil and chemical protection SOM of Argissols mainly in the surface layer of Coastal tablelands in brazilian northeast. Although the NT did not provide higher levels of SOM, the yield of green maize in commercial was significantly higher when adopting conservation systems.

2025, Forest Ecology and Management

The influence of soil aggregation as a means to protect soil organic carbon (SOC) from mineralization is unclear in very sandy soils. The dominant forest cover types in the Lower Coastal Plain of the US where sandy surface soils prevail are loblolly pine (Pinus taeda) and slash pine (Pinus elliottii var elliottii). The purpose of this study was to investigate the role that aggregation plays in C incorporation and sequestration in very sandy soils of the Lower Coastal Plain found under loblolly and slash pine ecosystems. Thirteen forest stands (seven loblolly pine; six slash pine) were used for this investigation. A sonic dismembrator was used to apply dispersive energy in order to destroy aggregates. The use of sonic energy was shown to be a valid tool for studying aggregates in sandy soils. The data showed that aggregates do not protect ASOC from mineralization in these very sandy soils. Loblolly pine surface mineral horizons accumulated 131% more TSOC than slash pine soil horizons. Slash pine soils had a 27% higher specific mineralization rate than loblolly pine soils; and Diffuse Reflectance Fourier Transform spectra (DRIFTS) showed that soils under loblolly pine were more aromatic than those under slash pine -and became more aromatic as mineralization proceeded. Due to their dominance in the Lower Coastal Plain of the US, pine ecosystems play an important role in the conversion of atmospheric CO 2 into the TSOC pool. However, soil aggregation should not be considered a mechanism to protect SOC in these very sandy soils when modeling soil carbon dynamics, even though slash pine systems show a slightly greater capacity to develop aggregates.