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BACKGROUND The effect of high-pressure homogenization (HPH) on the rheological and thermal properties, water retention capacity (WRC), morphology and in vitro digestion of wheat starch was evaluated. Starch suspensions (50 g kg-1 , w/w) were treated at increasing pressures (up to 100 MPa) and numbers of cycles (up to 5) to generate a wide range of energy densities (70-500 MJ m-3 ) delivered to the sample during processing. RESULTS High-pressure homogenization induced a partial starch gelatinization confirmed by higher digestibility. Gelatinization degree (GD) was between 13% and 83%, causing a wide range of functional properties. High-pressure homogenization-treated starch samples showed WRC values of 810-1910 g kg-1 . Storage modulus (G') and complex viscosity (η* ) of starch dispersions were almost two and three times higher than the control at 13% and 83% GD, respectively. Positive linear relationships between GD (R = 0.98, P

Plant roots release various organic materials that may modify soil structure and affect heat and mass transfer processes. The objective of this study was to determine the effects of a synthetic root exudate (SRE) on penetrometer resistance (PR), thermal conductivity (λ), hydraulic conductivity (k) and evaporation of water in a sandy soil. Soil samples, mixed with either distilled water or the SRE, were packed into columns at a designated bulk density and water content, and incubated for 7 days at 18°C. Soil PR, λ, k and evaporation rate were monitored during drying processes. Compared with those incubated with water, samples incubated with SRE had visible hyphae, greater PR (0.7–5.5 MPa in the water content range of 0.11 to 0.22 m3 m−3) and λ (0.2–0.7 W m−1 K−1 from 0.05 to 0.22 m3 m−3), and increased k in the wet region but decreased k in the dry region. SRE treatment also reduced the overall soil water evaporation rate and cumulative water loss. Analysis of X‐ray computed tomography (CT) scanning showed that the SRE‐treated samples had a greater proportion of small pores (

Polymer hydrogels, cross-linked polyacrylamide co-polymer (XPAM) and K-polyacrylate (XPAA), increase soil water availability under drought, but their long-term effects are unknown even though such knowledge is important for assessing economic feasibility at the farm-scale. This 9-yr, outdoor study amended an irrigated, calcareous silt loam with a one-time, 0.25% or 0.5% dry wt. (5.6 or 11.2 Mg/ha) application of either XPAM or XPAA; and included an untreated control and untreated, uneroded topsoil. Soil water retention and plant available water (PAW, g H2O per g dry soil) were measured in soil samples collected in spring for 7 of the 9 years. Across all years, the 2% XPAM produced the greatest PAW (0.318) and the PAW of other treatments followed in the order: 0.5% XPAM > 0.25% XPAM > Topsoil > 0.25% XPAA = 0.5% XPAA = control (0.224). In all years, the 0.25% XPAM and 0.5% XPAM treatments increased soil PAW relative to the control, i.e. their PAW ratios exceeded unity. Topsoil PAW exceeded that of the control in 6 of the 7 years measured. The PAW of 0.25% XPAM and 0.5% XPAM peaked in year one after application and declined linearly with time (P

Soil hydraulic properties control the provision of hydrological services. Vegetation and topography influence these properties by altering soil structure and porosity. The underlying mechanisms are not yet fully understood for the high Andean region. In this study, we examined how vegetation and topographic attributes are related to soil hydraulic properties and soil pore structure in young volcanic ash soils, and further correlated them to soil texture, organic carbon, and root characteristics to explain these relationships. In a 0.7 km2 study site located in the Andean páramo of northern Ecuador, we measured soil water retention, saturated hydraulic conductivity, bulk density (BD), and pore size distribution parameters on eight soil profiles with contrasting vegetation types (cushion-forming plants vs. tussock grasses) and topographic positions (summit vs. hillslope). We observed significant differences in soil hydraulic properties and soil pore structure in the uppermost horizons by vegetation type, whereas topography had a minor effect. In the A horizons, we found higher water retention at saturation and field capacity (10%–14%), higher total available water (8%–15%), and higher saturated hydraulic conductivity (4–12 times) under cushion-forming plants compared to tussock grasses. The elevated values under cushion plants were attributed to the presence of larger pores, lower soil BD, and higher soil organic carbon content as a result of coarser root systems. Total available water was generally high (0.34–0.40 cm3 cm−3), and locally not associated with any soil property. The higher water retention in soils under cushion vegetation can enhance soil water storage for plants and the regulation of water flows during prolonged rainfall events. The saturated hydraulic conductivity of the surface horizons is high compared to rainfall intensities resulting in high infiltration capacity; whilst its decline with depth reveals the potential for generation of subsurface stormflow, especially below cushion-forming plants. Our findings highlight that soil hydraulic properties differ among vegetation types, and show the significance of vegetation types for soil hydrology.

Wheat is a common crop, and its residues, such as wheat straw (WS) and wheat husk (WH), are typically recycled into farmland to improve water retention capacity. Water availability (in an unsaturated range) and soil water characteristic curves (SWCCs) require evaluations, but research has revealed little regarding the crack potential of dehydrated soil with added WS or WH composites. The current study investigated variations in crack intensity factor (CIF) caused by 1, 1.5, and 2% (w/w) WS and WH addition and modified the traditional SWCC model for applicability to soil mixed with WS or WH. The results revealed that the inclusion of WS and WH inhibits surface cracking, with maximum CIF reductions from 11.22 to 3.80%. Meanwhile, saturated moisture is improved by adding either WS or WH, and supplemented soil retains more water on average than pure soil under drought conditions. Moreover, a modified physical-based SWCC model applicable to determining SWCC for soil mixed with WS or WH composites is established by combining the traditional model with the soil capillary theory. The fitted results showed this modified SWCC model led to a better agreement than the traditional SWCC model between measurement and simulation. The hydraulic parameters in this modified model can be used as inputs in the soil-water movement simulation for soil–wheat residue composites.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]RIVAGE [ADD1_IRSTEA]Hydrosystèmes et risques naturels; International audience; The paper offers an analytical determination of the hydraulic properties of an unsaturated soil with reference to its retention curve, which describes the relationship between the volumetric water content and capillarity through matric suction. The analysis combines a particulate approach focused on the physics at the pore scale, including microstructural aspects, with a probabilistic approach where the void space and grain size are considered as random variables. In the end, the soil water characteristic curve of an unsaturated granular medium along a drying path can be derived analytically based on the sole information of particle size distribution. The analysis hinges on the tessellation of a wet granular system into an assemblage of tetrahedral unit cells revealing a pore network upon which capillary physics are computed with respect to pore throat invasion by a non-wetting fluid with evolving pendular capillary bridges. The crux of the paper is to pass from particle size probability distribution to a matching void space distribution to eventually reveal key information such as void cell and solid volume statistics. Making reasonable statistically based assumptions to render calculations tractable, the water retention curve can be readily constructed. Model predictions compare quite favourably with experimental data available for actual soils, especially in the high saturation range. Having a sound scientific basis, the model can be made amenable to address a variety of soils with a wider range of particle sizes.

Water plays a vital role in sustaining the natural functioning of the entire ecosystem that supports life on Earth. It plays key roles in the well‐being of society in numerous ways. However, climate variability and land use land cover (LULC) change have caused spatiotemporal water supply variation. Disentangling the effects of climate variability from LULC change on water supply is crucial for sustainable water resource management. The main purpose of this study is, therefore, to disentangle the relative contribution of LULC change and climate variability to the overall average annual water supply variation. Residual trends analysis combined with Integrated Valuation of Environmental Services and Tradeoffs (InVEST) annual water yield model was adopted to perform simulations and disentangle the relative impacts of climate variability and LULC change. Ground and satellite data were used in this study. The study area has experienced a significant increasing wetness trend and significant LULC dynamics between 2003 and 2017. As a result, an increasing water supply was observed due to the joint effects of climate variability and LULC change in the watershed (203 mm). The contribution of climate variability was 94%, whereas LULC contributes only 6% from 2003 to 2017. Climate variability negatively led to water supply variation while LULC change contributed positively from 2010 to 2017. Although the ongoing soil and water conservation (SWC) practices improved vegetation cover and water retention of the watershed, climate variability is the main driver of water supply variation. Therefore, SWC practices should incorporate ecosystem‐based climate change adaptation strategies and scale up to community‐based integrated watershed management to sustain water supply.

The effect of adding barley (Hordeum vulgare L.) β‐glucan (BBG) to dough on the water redistribution and the thermal properties of dough was studied by TGA and DSC. Combined with LF‐NMR to analyse the competition and redistribution mechanism of water at the ¹H level. The mass loss of the dough measured by TGA was reduced by an average of 2.11% with BBG added. BBG increased the water retention of the dough, delayed the water loss process. The LF‐NMR results showed that at the same water absorption the T21 of the 3% BBG dough was longer while its T22 was shorter than those of the control. BBG has different effects on the different states of water in the dough. BBG increased the free sulfhydryl content in dough during heating, while the adverse effects of BBG on the biopolymer reactions, such as disulfide bond, could be partially relieved by regulating water content.

Characterization of soil hydrodynamic properties is important for assessing the soil water regime. Ex situ measurements are costly and time consuming. Reflectance spectroscopy can rapidly estimate several soil properties, including soil water content (SWC). Here, we evaluated the ability of visible (vis) and near‐infrared (NIR) spectroscopy to assess the effects of soil texture and soil organic carbon (SOC) content on SWC. Thirteen undisturbed soil surface blocks were sampled in 2014 across the Brittany region, western France. Textural classes ranged from sandy loam to sandy clay loam texture, and SOC content ranged from 8.12 g kg−1 to 62.3 g kg−1. Aggregates of 3–4‐cm width and 5–6‐cm height were extracted and set at 10 matric potentials from saturation to permanent wilting point (1585 kPa). At given pressure heads, soil samples were scanned in triplicate to acquire reflectance spectra between 350 and 2500 nm. Spectra were converted into continuum removal and we focused on the absorption band near 1920 nm, which is linked to combination vibrations of water. We defined a new index based on the full width at half maximum (FWHM) of the absorption feature near 1920 nm. Results showed a linear relation between this NIR index and the volumetric SWC (R2 > 0.9) for every soil aggregate. The slope and the intercept of the line were correlated well with soil texture and SOC content. Results indicated that the parameters of this linear relation offer a new way to study SWC and water retention properties of soils in relation to their physical properties.

International audience; Hydraulic properties of soils, particularly water retention, are key for appropriate management of semiarid soils. Very few pedotransfer functions (PTFs) have been developed to predict these properties for soils of Mediterranean regions, where data are particularly scarce. We investigated the transferability of PTFs to semiarid soils. The quality of the prediction was compared to that for soils originating from temperate regions for which most PTFs were developed. We used two soil data sets: one from the Paris basin (French data set, n = 30) and a Syrian data set (n = 30). Soil samples were collected in winter when the water content was near field capacity. Composition and water content of the samples were determined at seven water potentials. Continuous- and class-PTFs developed using different predictors were tested using the two data sets and their performance compared to those developed using artificial neural networks (ANN). The best performance and transferability of thePTFs for both data sets used soil water content at field capacity as predictor after stratification by texture. The quality of prediction was similar to that for ANN-PTFs. Continuous- and class-PTFs may be transferable to other countries with performances that vary according to their ability toaccount for variation in soil composition and structure. Taking into account predictors of composition (particle size distribution, texture, organic carbon content) and structure (bulk density, porosity, field capacity) did not lead to a better performance or the best transferability potential.

The unsaturated soil hydraulic conductivity accounting for film flow is important for understanding soil hydrological and biological processes, especially in arid and semi‐arid regions. Recently, a theoretically based hydraulic conductivity model was developed to describe the hydraulic conductivity as a function of water content. We have used this model to compare seven soil water retention functions commonly used for predicting soil hydraulic conductivity due to film flow. A total of 30 soils, varying in basic properties, were selected from the Unsaturated Soil Hydraulic Database to evaluate the seven functions. The Webb method was applied to identify the critical soil matric potential (hc) below which thin film flow controls water movement. Soil hydraulic conductivity measurements at matric potential below hc were then used for curve fitting according to the seven functions. Slight differences were observed among the functions in predicting soil hydraulic conductivity due to film flow. Six of the seven functions in combination with the hydraulic conductivity model described the hydraulic conductivity due to film flow well, according to the terms of the coefficient of efficiency. The relatively poor performance of the one exception was due to the fact that the linear shape of the function made it less flexible at low matric potentials. In addition, the effect of textural class on its performance was substantial, showing a poorer fit for the sand soil compared with the loam and clay soils. These findings have important applications related to soil and water resources conservation especially in arid and semi‐arid regions.

Peat soils shrink and become very hydrophobic when dried. Both properties may cause inaccuracies when applying laboratory methods for soil hydraulic properties that have been developed and tested for mineral soils. This study aimed to compare different methods for the determination of the water retention of peat soils near permanent wilting point (pF 3.5 to 4.2). Three common methods were tested: two pressure apparatus (ceramic plate [Soilmoisture] vs. membrane [eijkelkamp]) and a dew-point potentiameter (WP4C, Decagon Devices, Inc.), which is based on the equilibrium of soil water potential with air humidity. We used both field-moist peat samples and samples that had been rewetted after oven-drying. We found that there was no systematic difference between the two pressure apparatus. Low moisture variability among replicates and dew-point potentiameter measurements that indicated a drainage to pF 4.2 support the use of pressure apparatus for the determination of water retention near permanent wilting point. Despite a rewetting time of 2 wk including periodic mixing, rewetted oven-dried samples showed lower soil moistures at pF 3.5 and 4.2 than field-moist ones. This severe and long-lasting hysteresis effect was strongest for less decomposed peat samples. Thus, field-moist samples should be used. This makes the classical dew-point potentiameter measurement protocol, which is based on defined water additions to oven-dried samples, unsuitable for peat samples.

In this study, we explored four approaches to infer field-saturated hydraulic conductivity (Kfₛ) from both early-time and steady-state infiltration measurements using an explicit expression for three-dimensional flow. All approaches required an estimate of the soil capillary length, λ. Approach 1 estimated Kfₛ via optimization, in which all other infiltration parameters (9 in total) were known. The remaining approaches constrained λ through different interpretations of coefficients generated by linear regression between infiltration and time. Approach 2 utilized these coefficients plus estimated soil water content to simultaneously quantify both λ and Kfₛ. Approach 3 used an analytical expression in which λ was estimated based on water retention/unsaturated hydraulic conductivity parameters, while Approach 4 adopted a universal λ value of 15 cm. The accuracy of these four approaches were tested using numerical and laboratory infiltration data. Approach 1 had the highest accuracy but also required the most auxiliary data, making it most suitable for laboratory and numerical experiments. Approach 2 was the least consistent, providing negative estimates for λ and Kfₛ under certain conditions. Approach 3 also gave accurate predictions of Kfₛ, but may be inaccurate in instances where the water retention model parameters are uncertain or do not describe soil hydraulic behaviors well. Approach 4 provided reasonable estimates of Kfₛ (within a factor of three from the actual value in most cases), while not requiring additional observational data. The optimal approach for interpreting Kfₛ will thus vary depending on the type and quality of available auxiliary data.

Soil water retention data are fundamental in soil modeling studies. Temperate pedotransfer functions (PTFs) have been commonly used to estimate water retention of Brazilian soils, mainly because of the lack of soil data for Brazil. However, these PTFs may not be suitable for tropical or subtropical conditions such as those found in Brazil. The objective of this study was to establish a dedicated Hydrophysical Database for Brazilian Soils (HYBRAS) suitable for PTF development. Data present in HYBRAS comprise 445 soil profiles with 1075 samples and are representative of a wide range of Brazilian soils. The data are organized in a relational structure of tables that cover general site descriptions, land cover, and hydrophysical and chemical measurement methods. Raw data (e.g., water retention points covering the 0–15,000-cm suction range) and derived data are included in the tables. Another objective of this study was to use the database to compare the accuracy of water retention estimates based on PTFs developed for Brazilian and temperate regions. In general, the Brazilian PTFs performed better than the temperate models, especially for weathered (Ferralsols, Acrisols, and Nitisols) fine-textured (clay, sandy clay, clay loam, silty clay loam, and silty clay) soils. Silt content was not a successful criterion for distinguishing performance of Brazilian and temperate PTFs for Brazilian weathered soils. The water retention of weathered soils was shown to differ from that of temperate soils due to differences in pore structure resulting from their clay content and mineralogical nature, thus confirming results reported in the literature.

Soil structure-dependent properties are subject to changes with time and depth under the influences of agronomic practices and environmental factors. Wetting and drying (W/D) cycles following tillage alter the structure and pore-related functions of field soils. This study investigates the effects of W/D cycles on temporal changes of soil porosity and water retention curves (SWRCs) of a tilled layer (0- to 15-cm) during a post-tillage period. Soil volumetric water content (θ) and matric potential (ψₘ) dynamics at three depths were monitored continuously, and the total porosity (Pₜ) was determined gravimetrically. Nine W/D cycles were identified in the experimental period. Soil Pₜ decreased gradually with time and depth and became relatively stable after four W/D cycles, and the SWRCs shifted toward higher θ values at a specific ψₘ. The magnitude of SWRC change was relatively small during the first to third W/D cycles when the degrees of saturation were relatively low, reached the maximum after the fourth W/D cycle during which the soil was nearly saturated, and became less significant thereafter. Soil water holding capacity was improved during the W/D processes mainly due to the reduction of effective porosity and development of residual porosity. During the earlier four W/D cycles, a higher initial θ also contributed to the increase of the residual porosity, and thus enhanced the soil water holding capacity. The difference, however, tended to disappear in later W/D cycles. The data show clearly that the θ–ψₘ relationships following tillage are dynamic.

In this study, a superabsorbent polymer (SAP; Super-AB-A-200) was used for the amendment of the water-holding capacity of soil on a steep surface. Three concentrations of SAP [0.20, 0.40 and 0.60% (w w−1)] and a control (0%) were blended with sandy soil. This study aimed to evaluate the evaporation rate, water retention capacity and saturated water content of polymer-treated soils for determining plant survival and seed germination rate through cylinder and steep surface experiments. The results demonstrated that sandy soil treated with SAP showed significantly enhanced soil water holding compared with the controls. Furthermore, the seed germination rate was significantly higher in polymer-treated soils than in the controls. The survival times of grass and ligneous plants were lengthened under water stress conditions. Finally, treatment with 0.40% SAP was the optimum selection for sandy soil amendment on steep surfaces.

Superabsorbent polymer (SAP) efficiency in water absorption and release depends on soil properties and SAP type and concentration. Our objective was to examine the effects of soil texture, SAP concentration and properties on water absorption and release from soil–SAP mixtures during 10 h of drying. Four SAP types, five SAP concentrations, and five soils were used. Initial water quantity absorbed by SAPs (53–171 g g⁻¹ of SAP) was more than two orders of magnitude greater than that absorbed by soils (0.35–0.53 g g⁻¹ of soil). Water absorption by soil–SAP mixtures (i) significantly improved water holding capacity relative to the soil, and (ii) increased with an increase in SAP concentration and soil clay content. The ability of soil–SAP mixtures to retain water after 5 h of drying relative to the initial water content was greater than that of the soils alone, especially in coarse-textured soils. After 5 h of drying, the specific amount of water retained by a unit weight of SAP in the soil–SAP mixture was higher than that at 0 h. This observation suggests a continued absorption of water by SAPs from soils during the first 5 h of drying. The fraction of water loss from SAP with large-size beads (BJ-2101M) was smallest in all the mixtures among the four SAPs after 10 h drying. Our results showed that addition of SAPs to soils not only decreases water loss to evaporation from soils but also from the SAPs, especially for a SAP with large size beads.

Biohydrogels such as microbial exudates and root-derived mucilage are soil-born cross-linked polymers, able to form porous three-dimensional networks during water uptake. The gel effect is the variation of soil properties, such as soil hydrology and soil structural stability, resulting from biohydrogel swelling in soil. Conventionally, soil–water–hydrogel interactions are investigated by measuring soil bulk properties such as water retention curves and porosity, without further analyzing the effect of biohydrogel phases in soil on a quantitative basis. Therefore, the evaluation of advanced and novel methods for the characterization of biohydrogel phases in soil and soil–water–hydrogel interactions is necessary. This review evaluates currently available methods for their potential to analyze processes associated to the gel effect. A promising approach to investigate the spatio-temporal distribution of biohydrogel phases in porous media is based on Nuclear Magnetic Resonance (NMR) such as 1H-NMR relaxometry, as well as on imaging techniques such as Environmental Scanning Electron Microscopy (ESEM). Especially NMR techniques enable the identification of different water populations based on their differences in the relaxation, and thus the mobility of water molecules in biohydrogels and non-gel water in soil pores. Rheology measures the flow behavior of biohydrogels, providing information on the structural behavior of the hydrogel network and its gelling mechanism. Soil rheology further quantifies the effect of the biohydrogel phases on the interactions between soil particles, and thus the impact on soil microstructural stability. However, rheology does not elucidate the spatio-temporal distribution and structural state of biohydrogel phases in soil. All in all, a systematic combination of rheology, NMR and suitable imaging methods seems promising and necessary in order to elucidate the still widely unknown gel effect in soil.

This article investigates the impact of ultrasound as pretreatment for enzymatic hydrolysis of cellulose from sugar beet shreds and uses modeling of the experimental results. Ultrasound pretreatment with different power input, duration, duty cycle, and solids load was applied to sugar beet shreds. Ultrasound under investigated conditions provided substrates with different characteristics. At applied conditions, ultrasound caused up to 28% material solubilization while cellulose recovery was approximately 90%. Pretreated substrates had multiple times higher values of water retention (WRV) than untreated one. Ultrasound pretreated sugar beet shreds were more susceptible to cellulases adsorption than the untreated ones having 1.4 to 15 times higher maximum adsorption capacity (σ). Statistical modeling of the results of enzymatic hydrolysis revealed that parameters with significant influence on the reducing sugars yield were interaction between σ and cellulose recovery, then σ and WRV as mutually independent parameters, as well as interaction between WRV and σ. The highest achieved yield of cellulose hydrolysis was 3.7 times higher than that obtained with untreated sugar beet shreds and it amounted approximately 780 mg/g cellulose. © 2017 American Institute of Chemical Engineers Environ Prog, 2017

Controlled drainage can reduce nitrate export from tile drainage flow, but its impact on phosphorus (P) loss is largely unknown. We compared P leaching from soil cores treated as free drainage (FD) or controlled drainage (CD) before and after manure application. In August 2012, 16 intact cores (45 cm long, 15 cm diameter) were collected from a grass forage field () located in Chazy, NY, and modified for drainage control and sampling. In Experiment 1 (no manure), initial leachate was defined as FD, and leachate collected 21 d later (valves closed) was considered CD. In Experiment 2, seven cores were randomly assigned to CD or FD. Liquid dairy manure was applied at 1.2 × 10 L ha, followed by simulated rainfall 2 h later. Leachate was sampled on Day 7, 14, and 21. Deionized water was applied at 3.4 cm h over 1 h to mimic a 10-yr rainfall event. Total P (TP), soluble reactive P (SRP), dissolved oxygen, iron (Fe), and pH were measured. Results showed that TP ( = 0.03) and SRP ( = 0.35) were lower for CD prior to manure application. Manure application caused 36- and 42-fold increases in TP and SRP; however, TP was lower for CD at 7 ( = 0.06), 14 ( = 0.003), and 21 d ( = 0.002) of water retention. Mean SRP for CD was nearly 40-fold lower than FD by Day 7 ( = 0.02) and remained low, suggesting CD in the field may reduce P export risk to tile drain flow after manure applications.

The soil freezing characteristic curve (SFCC) defines the relationship between soil temperature and unfrozen water content. This curve is important for predicting water flow and heat conduction in frozen soils, as well as freezing heave and thawing settlement. So far, SFCCs reported in the literature were usually determined at zero stress. To investigate stress effects on SFCC, a stress- and temperature-controlled triaxial apparatus was developed in this study. The unfrozen volumetric water content was measured using a newly developed noninvasive time domain reflectometry (TDR) probe. The new apparatus was used to measure SFCCs of two typical soils (i.e., clay and sand) at different stress conditions (i.e., 30, 100, and 200 kPa). Each specimen was subjected to compression, and then a cycle of freezing and thawing. As expected, for both soils, the saturated water content prior to freezing was smaller at higher stresses because of compression. During the subsequent freezing and thawing, the soil specimen at a higher stress was able to retain more liquid water than that at a lower stress. The higher unfrozen water retention capacity at higher stresses is mainly because the pore size of a soil specimen becomes smaller during compression. Hence, more water can retain a liquid state due to the enhanced capillarity. On the other hand, stress effects on the SFCC were found to be more significant for clay than for sand. This is likely because the stress-induced change in pore size distribution is larger in clay due to its higher compressibility.

The pore size distribution (PSD) of biopolymeric-amended soils is rarely investigated due to difficulties in its quantification using classical methods. In this study, we analyzed the impact of biopolymeric soil amendments on the PSD of a dryland loamy soil based on its physical and biological properties using a completely randomized design with four treatments consisting of two different dosages (10 and 5 g kg−1) of two different biopolymers, (chitosan [CH] and Arabic gum [AG]) plus a reference soil. To determine the effects of CH and AG on the PSD, nuclear magnetic resonance relaxometry (NMRR) measurements were used to determine the longitudinal (T1) and transversal (T2) relaxation times. A set of soil structure–related characteristics was also determined in the laboratory. The results revealed that T2 spectra provided a good proxy to determine the PSD, showing good agreement between the PSD from T2 spectra and that calculated from the water retention curve (WRC) (R2 > 0.78; RMSE