Silt Loam Soil Research Articles

Soil health, microbial communities, and annual ryegrass yield under contrasting management practices

AbstractBiological indicators are often used to evaluate the effect of management practices on soil health. However, determining which indicators can detect changes in soil health after implementation of conservation practices and how these indicators relate to plant growth in grass seed production systems remains unclear. The goal of this study was to explore the relationships between management practice history, soil health metrics, plant growth, and soil microbial communities in annual ryegrass grown under greenhouse conditions. Soils were collected from 12 annual ryegrass [Lolium multiflorum (L.) Husnot] fields managed under conventional (till/bale) or conservation (no‐till/full straw) management practices, with three silt loams and three silty clay loams collected for each practice. Annual ryegrass was grown for 5 months on each of the 12 soils in a greenhouse. Soils with a history of conservation management improved the majority of the carbon cycling‐related metrics for the silt loam soils. Management practices had no effect on seed yield, however, conservation management significantly improved aboveground biomass in silty clay loam soils. Contrasting management practices resulted in distinct microbial communities, making them sensitive indicators of changes in soil conditions. Soil health and plant metrics were positively associated with the microbial communities in soils under conservation management. Total C and organic matter were positively correlated to plant parameters in silt loams, while few indicators were correlated to plant metrics in silty clay loams. These results highlight the complex interplay between microbial communities, soil health, and plant growth and the importance of considering inherent soil properties like texture.

Model of Soil Particles to Investigate Shear Stress and Deformation in Silt Loam and Silt Clay Soil Using Finite Element Method

Model of Soil Particles to Investigate Shear Stress and Deformation in Silt Loam and Silt Clay Soil Using Finite Element Method

Did cover crop or animal manure ameliorate corn residue removal effects on soil mechanical properties after 10 years?

Crop residue removal may negatively affect soil mechanical properties, which are key components of soil quality. To evaluate potential long-term effects, we assessed the 10-yr impact of corn (Zea mays L.) residue removal (59 % of non-grain biomass annually) on surface soil mechanical properties (0–20 cm). We also evaluated whether adding carbon (C) amendments, such as using a winter rye (Secale cereale L.) cover crop or surface-applying cattle manure (24 Mg ha−1 biannually) can ameliorate the effects of crop residue removal. This long-term study was under irrigated no-till continuous corn on a silt loam soil in south-central Nebraska, USA. Measurements included soil penetration resistance, field bulk density, aggregate strength, Atterberg limits (liquid limit, plastic limit, and plasticity index), Proctor maximum bulk density, and the water content at which the Proctor maximum bulk density (critical water content) occurs. Reduction in soil organic carbon (SOC) concentration explained most of the changes in soil mechanical properties. Long-term corn residue removal increased penetration resistance (+40 %) for the 0–20 cm depth, and reduced aggregate strength (−44 %), plasticity index (−22 %), and critical water content (−13 %) in the 0–5 cm depth. Residue removal also reduced field bulk density (−5%), liquid limit (−12 %), and plastic limit (−10 %) in the 0–10 cm depth, but increased Proctor maximum bulk density (+8 %) in the 0–5 cm depth. Winter rye cover crop reduced field bulk density (−5%, 0–15 cm depth) and increased penetration resistance (+52 %, 0–20 cm depth). Surface-applied manure amendments increased the near-surface soil liquid limit (+8 %) and plastic limit (+8 %) in the 0–5 cm depth. Given the high rate of residue removal used in this experiment, our findings support that excessive corn residue removal over the long-term (∼10 years) negatively affects near-surface soil mechanical properties, but that use of winter rye cover crop or surface-applied manure can minimally to partially ameliorate these effects.

Biobased residues sustain crop productivity and soil health in a maize–soybean rotation

AbstractBiobased residues are local and cost‐effective sources of soil amendments that can efficiently provide nutrients to crops, enhance soil health and serve as alternatives to mineral fertilizers. The objective of our study was to comprehensively evaluate the soil health and crop productivity of temperate agroecosystems amended with different types of organic residues (biobased residues), including composted food waste (compost), biosolid slurry (biosolids) and liquid anaerobic digestate (digestate), compared with nitrogen fertilizer. The experiment was conducted on a silt loam soil under maize–soybean rotation in Canada, where a wide range of physical, chemical and biological indicators were measured and integrated into a soil health score. Biobased residues resulted in about 50%–60% increase in soil‐exchangeable potassium and 10% soil‐exchangeable sodium over levels found in nitrogen fertilizer. Soil microbial biomass and the capacity of soil microbes to utilize carbon substrates differed among growing seasons but not among amendment types (p > .05). Crop productivity was similar among amendment types (p > .05). We found that the soil health score of biosolids was positively correlated with shoot and root biomass and negatively correlated with shoot nitrogen (p < .05), while that of nitrogen fertilizer was positively correlated with shoot carbon (p < .05). This was likely because of a variation in the availability of labile carbon and nitrogen among amendment types. Our research also suggests that temperate silt loam soil amended with biobased residues, especially biosolids, supplied sufficient nitrogen without the need for additional nitrogen fertilizer.

An Approach for Easy Detection of Buried FRP Composite/Non-Metallic Pipes Using Ground-Penetrating Radar.

Pipelines remain the safest means of transporting natural gas and petroleum products. Nonetheless, the pipeline infrastructure in the US is facing major challenges, especially in terms of corrosion of steel/metallic pipes and excavation damage of onshore pipelines (leading to oil spills, explosions, and deaths). Corrosion of metallic pipelines can be avoided by using non-corrosive materials such as plastic pipes for low-pressure applications and glass-fiber-reinforced polymer (GFRP) composite pipes for transporting high-pressure oil and natural gas. However, buried non-metallic pipelines are not easily detectable, which can lead to increased excavation damage during construction and rehabilitation work. Alternative strategies for making buried non-metallic pipes easily locatable using ground-penetrating radar (GPR) were investigated in this study. Results from this study have shown that using carbon fabric or an aluminum foil overlay on non-metallic pipes before burying in soil significantly increases the reflected GPR signal amplitude, thereby making it easier to locate such pipelines. The reflected GPR signal amplitude for pipe sections with carbon fabric or aluminum foil overlays was found to have increased by a factor of up to 4.5 over the control samples. The results also highlight the importance of selecting the appropriate antenna frequency for GPR surveys, since wet silt loam soil and clay significantly reduce the penetration depths of the radar signals produced by the GPR antennae.

Validating coupled flow theory for bare‐soil evaporation under different boundary conditions

AbstractEvaporation from bare soil is an important hydrological process and part of the water and energy balance of terrestrial systems. Modeling bare‐soil evaporation is challenging, mainly due to nonlinear couplings among liquid water, water vapor, and heat fluxes. Model concepts of varying complexity have been proposed for predicting evaporative water and energy fluxes. Our aim was to test a standard model of coupled water, vapor, and heat flow in the soil using data from laboratory evaporation experiments under different boundary conditions. We conducted evaporation experiments with a sand and a silt loam soil and with three different atmospheric boundary conditions: (i) wind, (ii) wind and short‐wave radiation, and (iii) wind and intermittent short‐wave radiation. The packed soil columns were closed at the bottom (no water flux) and instrumented with temperature sensors, tensiometers, and relative humidity probes. We simulated the evaporation experiments with a coupled water, vapor, and heat flow model, which solves the surface energy balance and predicts the evaporation rate. The evaporation dynamics were predicted very well, in particular the onset of stage‐two evaporation and the evaporation rates during the stage. A continuous slow decrease of the measured evaporation rate during stage‐one could not be described with a constant aerodynamic resistance. Adding established soil resistance parametrizations to the model significantly degraded model performance. The use of a boundary‐layer resistance, which takes into account the effect of point sources of moisture, improved the prediction of evaporation rates for the sandy soil, but not for the silt loam.

Tillage homogenizes soil bacterial communities in microaggregate fractions by facilitating dispersal

Soil aggregation physically protects soil organic matter and promotes soil carbon persistence through microaggregate formation and organo-mineral associations. Tillage is a ubiquitous disturbance to arable soil that disrupts aggregation, thus affecting microbial resource availability, soil microhabitat conditions, and microbial interactions. We investigated how tillage affects bacterial community composition of soil microaggregate fractions (53–250 μm), specifically the free microaggregate fraction in bulk soil and the occluded microaggregate fraction within macroaggregates, using two long-term tillage vs. no-tillage experiments in southern WI, U.S., that represent two different silt loam soils (Alfisol and Mollisol). We applied 16S rRNA gene amplicon sequencing to characterize the effects of tillage on microaggregate bacterial communities by relating compositional changes and ecological community assembly patterns to various tillage-driven changes in the soil environment, including aggregate size distribution and carbon content. Tillage homogenized soil bacterial communities, as quantified by increased compositional similarity at both within-plot and between-plot scales, and community assembly was increasingly influenced by homogenizing dispersal with tillage. We did not identify major distinctions between bacterial communities of the free and occluded microaggregate fractions, thus highlighting how soil microaggregates readily shift between these operationally defined fractions in temperate annual cropping systems, where the soil environment is subject to drastic seasonal changes that are exacerbated by tillage. By identifying influential community assembly processes and analyzing communities in microaggregate fractions, we improve our understanding of the microbial response to soil disturbance, and thus the potential mechanisms through which disturbances like tillage affect soil carbon persistence.

Soil Microclimate and Persistence of Foodborne Pathogens Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica Newport in Soil Affected by Mulch Type

Mulching is a common agricultural practice that benefits crop production through soil moisture retention, weed suppression, and soil temperature regulation. However, little is known about the effect of mulch on foodborne pathogens present in soil. In this study, the influence of polyethylene plastic, biodegradable corn-based plastic, paper, and straw mulches on Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica Newport populations in soil was investigated. Silt loam soil in troughs was inoculated with a cocktail of the pathogens and covered with mulch or left bare, then incubated for 21 days, during which bacteria were enumerated and environmental parameters monitored. Bacterial counts declined in all treatments over time (p < 0.001) but persisted at 21 days at 0.8–0.95 log CFU/g. Pathogens also declined as a factor of mulch cover (p < 0.01). An exponential decay with asymptote model fit to the data revealed slower rates of decline in soil under mulches for all pathogens (p < 0.05) relative to bare soil. Compared to the average for all treatments, rates of decay in bare soil were 0.60 (p < 0.001), 0.45 (p < 0.05), and 0.63 (p < 0.001) log CFU/g/d for E. coli O157:H7, L. monocytogenes, and Salmonella, respectively. Linear multiple regression revealed that soil hydrological parameters were positively correlated (p < 0.05) with bacterial counts, while day soil temperatures were negatively correlated (p < 0.001), suggesting that higher day temperatures and lower moisture content of bare soil contributed to the faster decline of pathogens compared to mulched soil. A microcosm experiment using field soil from lettuce cultivation suggested no influence of prior mulch treatment on pathogens. In summary, pathogen decline in soil was modified by the soil microclimate created under mulch covers, but the effect appeared was restricted to the time of soil cover. Slower decline rates of pathogens in mulched soil may pose a risk for contamination of fresh market produce crops.

Physiological responses of coffee (Coffea arabica L.) plants to biochar application under water deficit conditions

Water deficit is one of the main abiotic stressors in crop production. The development of strategies to improve plant tolerance to water deficits has gained importance. Biochar application can be considered an alternative to mitigate abiotic stress. The use of coffee pulp to produce biochar could be a novel strategy for improving drought tolerance in coffee crops. Coffer plants cv. ‘Castillo’ were grown in pots or PVC pipes filled with silt loam soil in two separate experiments to evaluate the effect of coffee pulp biochar application on physiological responses under water deficit conditions. Four different biochar doses (0, 4, 8, and 16 t · ha-1) were used. A water deficit was imposed through progressive reduction irrigation (25%, 50%, 75%, and 90% of water lost via evapotranspiration). The leaf gas exchange, maximum quantum yield of PSII (Fv/Fm), biomass, and water status were measured. Reduced irrigation negatively affected the Fv/Fm, leaf gas exchange, biomass, and water status. Biochar (8 t ha-1) increased photosynthesis in both well-irrigated plants (6 µmol m-2 s-1) and with reduced irrigation (3.5 µmol m-2 s-1) compared to 0 t ha-1 biochar (reduced irrigation: 1.8 µmol m-2 s-1 and well irrigated: 3.9 µmol m-2 s-1). In conclusion, 8 t ha-1 biochar can be a recommended practice for coffee production, not only to capture carbon and reintroduce it to the soil, but also to alleviate the effects of moderate water deficit. In future investigations, biochar application can be evaluated as an alternative to soil management or coffee plant nutrition, and its interaction with drought stress scenarios.

Contrasted effects of biochar application on interrill erosion depending on age, application rate and soil type

Besides its carbon sequestration potential, biochar can mitigate soil erosion through improved soil structure. However, the short-term erosion mitigation potential of biochar remains debated, while it is unknown in the long-term. The aim of this study was therefore to determine the impact of biochar application on soil interrill erosion parameters, and to assess whether this impact depends on biochar age and application rate for two different soils. To assess the short-term impact, experiments were performed with topsoil from cultivated silt loam and sandy loam soils enriched with fresh biochar at rates of 1% w/w (13.5 T ha−1) and 2% w/w (27 T ha−1). In the same fields, soil from former kiln sites containing 19th century-old biochar was used to assess the long-term impact. Aggregate stability was measured according to Le Bissonnais (1996). Runoff and soil loss were measured in a flume under simulated rainfall. On the sandy loam soil, old biochar and 2% fresh biochar improved aggregate resistance to slaking. For the same soil, old biochar increased the time to runoff by 55%. For both study sites together, old biochar reduced the final runoff rate by 48%, whereas 2% fresh biochar reduced the final soil loss rate by 39%. Overall, the positive impact of biochar on interrill erosion was clearly more pronounced for the sandy loam soil compared to the silt loam soil. These contrasted results call for further studies across a wider variety of soil types.

Effects of pelleted sugarcane biochar applications on growth, yield and economics of rainfed corn (Zea mays L.) in the Mississippi Delta

Applying biochar as a soil remediation source can improve soil fertility and physico-chemical properties, there by impacting crop yields. Therefore, the objective of this field study was to assess rainfed corn (Zea mays L.) production benefits of sugarcane bagasse biochar at five application rates (0, 5, 10, 15, and 25 t ha−1) in a Dundee silt loam soil in 2019-2021. The effects of biochar on rainfed corn growth, grain yield, and grain quality were examined. Biochar significantly improved grain yields in the second and third years of application. Grain yield increases varied between 5.4 % and 12.6 %, and 8 % and 16.0 % in 2020 and 2021, respectively. In the third year, grain yields were 10.64, 11.50, 11.97, 12.14, and 12.35 t ha−1 at 0, 5, 10, 15, and 25 t ha−1 biochar levels, respectively. Grain quality was impacted by biochar application for protein and oil content. This study demonstrated that successive biochar applications at 5 t ha−1 and higher rates can enhance corn grain yield under rainfed conditions by improving the plant available water in the root zone, benefiting corn growers. These improved grain yields with biochar did not translate to increased net returns due to the disproportionate increase in production costs, mainly due to the costs associated with large quantities of biochar application. However, the potential benefits of longer-term continuous use of biochar in corn production merit further investigation as producers are concerned about the availability, distance between the field of application and source, and quantity required for a significant impact on farm returns.

Effect of soil hydrophobicity on soil-water retention curve of a silt loam soil

Soil wettability is an important property that affects the behaviour of fine-grained soils. Previous studies have shown that hydrophobicity induced by organic or silane additives may affect the soil-water retention curve (SWRC). However, current findings regarding the effect of hydrophobicity on the SWRC are controversial. Previously, organic or silane additives were assumed to change only the soil wettability. Nevertheless, this study shows that polyvinyl alcohol (PVA) can change the hydrophobicity, pore size distribution (PSD), and specific surface area (SSA) of soil, thus affecting the SWRC. PVA-treated soil is hydrophobic when cured at 20 ℃, but hydrophilic when cured at 100 ℃. No thermal degradation is indicated in the PVA at 100 ℃ based on thermogravimetric analysis and a comparison of mass loss, and the sole difference between the PVA-treated soils cured at 20 and 100 ℃ is their wettability. This study managed to make the hydrophobicity caused by PVA to become an independent variable separated from the PSD and SSA by controlling the ambient temperature. The wetting and drying curves are measured under isopiestic humidity control in the high-suction domain (2.7–298.7 MPa), whereas pressure plates are used for the drying curves in the low-suction domain (0–800 kPa). The results obtained indicate that soil hydrophobicity significantly accelerates drainage when the matric suction is between 100 and 400 kPa, and an increase in PVA content increases the water retention capacity of soil. When the matric suction exceeds 2.7 MPa, the effect of soil hydrophobicity on the SWRC of the soil weakens. At this time, the SWRC is dominated by the van der Waals force, and the SSA contributes significantly to the process. Additionally, this study enables some controversial findings from previous studies to be explained, which is of great significance in soil and agriculture sciences.

Response of biochar derives from farm waste on phosphorus sorption and desorption in texturally different soils

The information on changes in phosphorus (P) sorption and desorption characteristics and transformations after biochar application to high P fixing soils is still unclear. In the present study, we evaluated the differential response of biochar derives from five different farm waste viz. Lucaena sp., Albbizia sp., Mangifera indica, Triticum aestivum and Oryza sativa applied at 1 and 3 g kg−1 (w/w) on P sorption and desorption in three texturally different (silt loam, clay loam and sandy loam) soils. The amount of P sorbed by the clay loam was significantly (p<0.05) higher than the silt loam and sandy loam, regardless of added P concentration. The Freundlich isotherms exhibit a better fit (R2 = 0.564–0.996 in silt loam, 0.640–0.993 in clay loam and 0.724–0.993 in sandy loam soil) to P sorption data as compared with the Langmuir isotherm. Biochar application significantly decreased the P desorption maxima and desorption constant. The R2 values ranged from 0.447 to 0.999 in silt loam, 0.438 to 0.996 in clay loam, 0.545 to 0.989 in sandy loam. Lucaena biochar showed highest adsorption maxima, thereby suggesting highest P release, whereas soils treated with Triticum aestivum biochar had the lowest adsorption maxima in both clay loam and sandy loam soil. These results indicated that biochar application can significantly enhance P availability; the extent of which is determined by soil texture and type of biochar. The results of present study highlight that biochar application would help increase soil P availability by enhancing fertilizer-P use efficiency associated with decreased P sorption capacity due to increased flush of available-P in soil colloidal complex.

Influence of manure and tillage on soil carbon and soil organic matter in silt loam soils of corn–soybean–forage systems

AbstractIntroductionAn increasing number of farms in Northeast Ohio are being managed under reduced or conservation tillage practices, while those under conventional or intensive tillage are decreasing. Additionally, the use of on‐site farm manure among the growers is commonplace. Therefore, it is important to understand how the various management practices of these farms are impacting soil health, soil carbon stocks and crop yields.Materials and MethodsThis on‐farm study takes place in the temperate climate of the midwestern United States on a silt loam soil. It focuses on the impact of tillage (mouldboard plough [MP], vertical/chisel tillage [VT] and no‐tillage [NT]) and fertilizer (manure included or not) management practices on soil properties. Twelve agriculture fields and two woodland sites, for reference, on Canfield silt loam soils were selected for assessment in this project. Corn (Zea mays L.)–soybean (Glycine max L.) rotations and mixed forage Hayfields were the crops considered. Crop yields at each farm along with soil organic matter (SOM), total carbon (TC), total nitrogen (TN), bulk density, pH, soil test phosphorus (P), potassium (K) and sulphur (S) were assessed at two depths, 0–15 and 15–30 cm. Results of the first 2 years of the study (2020 and 2021) are presented here.ResultsAt the surface soil depth (0–15 cm), TC content was not different among cultivated fields (36 Mg ha−1), but was significantly less than Hayfields, which had the same amount of TC as the wood sites (58 Mg ha−1). There was no significant difference in soil test P, K or S due to tillage. Analysis of variance revealed no statistical difference due to fertilizer. At the soil surface depth, principal component analysis, supported by analysis of similarities (ANOSIM), determined that measurements of TC, TN and SOM distinguished a difference in Hayfields compared to cultivated fields (R‐statistic = 0.33; p = 0.001), but little difference when the 15–30 cm soil depth was considered (R‐statistic = 0.17; p = 0.001). ANOSIM also determined a slightly significant (R‐statistic = 0.065; p = 0.031) difference in fertilizer at the deeper soil depth. Correlation analysis revealed a strong positive relationship between SOM and corn grain yield (r = 0.59) and TN and corn grain yield (r = 0.39).ConclusionsThere was no significant loss of TC among increasing tillage intensities possibly due to the inclusion of manure fertilizer in tilled fields even though there were only slight statistical differences between fields that utilized manure and those that did not. The use of manure was not detrimental in terms of soil test P for most farms, but should be used judiciously. Inclusion of perennial crops such as hay in rotation with crop production can improve TC and TN content. Finally, increasing SOM could potentially increase corn grain yield, but no causal relationship has been determined yet.

Field-scale assessment of direct and indirect effects of soil texture on organic matter mineralization during a dry summer

Soil texture plays a crucial role in organic matter (OM) mineralization through both direct interactions with minerals and indirect effects on soil moisture. Separating these effects could enhance the modelling of soil organic carbon (SOC) dynamics under climate change scenarios. However, the attempts have been limited small-scale experiments. Here, we studied the effects of soil texture on added OM mineralization in loamy sand, loam and silt loam soils in nine agricultural fields in Flanders, Belgium. Soil moisture, temperature, groundwater table depth and the mineralization of 13C-labeled ryegrass were monitored in buried mesocosms for approximately three months during a dry summer. Ryegrass-C mineralization was lowest in the loamy sand (39 ± 7 %) followed by silt loam (48 ± 7 %) and loam (63 ± 5 %) soils, challenging the current clay%-based moderation of C-mineralization rates in soil models. Soil temperature was not influenced by soil texture, whereas soil moisture was indeed dependent on soil texture. It appears that capillarity sustained upward water supply from groundwater to the topsoil in loam and silt loam soils but not in loamy sand soil, although this difference in capillary rise could not fully explain the higher moisture content in loam than that in silt loam soils. Additionally, soil texture only impacted remnant added ryegrass pieces (>500 μm) but not the finer ryegrass-derived SOC (<500 μm), which might point at the important indirect control of texture on OM mineralization during prolonged summer drought. However, these effects are only manifested during drought when no other factors (e.g., groundwater depth or subsurface water flows) exert an overriding impact on the soil water balance. Overall, our findings highlight the need to properly incorporate the indirect effects of soil texture on OM mineralization into soil carbon models to accurately predict soil C stocks under future climate change scenarios.

Effect of continuous sugarcane bagasse-derived biochar application on rainfed cotton (Gossypium hirsutum L.) growth, yield and lint quality in the humid Mississippi delta

Optimizing soil health through soil amendments is a promising strategy for enhancing rainwater efficiency for stabilizing crop production. Biochar, obtained by torrefaction of sugarcane bagasse, a byproduct from sugar mills, has a high potential for its use as a soil amendment, which can boost crop yields, but needs further field trials for its adoption in farming systems. A field study was conducted during 2019–2021 at Stoneville, Mississippi, to assess rainfed cotton (Gossypium hirsutum L.) production under four biochar levels (0, 10, 20, and 40 t ha−1) on Dundee silt loam soil. The effects of biochar on cotton growth and lint yield and quality were examined. Biochar levels had no significant impact on cotton lint and seed yield for the first two years. Still, in the third year, a significant increase in lint yield by 13 and 21.7% was recorded at 20 and 40 t ha−1 biochar levels, respectively. In the third year, lint yields were 1523, 1586, 1721, and 1854 kg ha−1 at 0, 10, 20 and 40 t ha−1 biochar levels, respectively. Similarly, cotton seed yield increased by 10.8% and 13.4% in 20 and 40 t ha−1 biochar plots. This study demonstrated that successive biochar applications at 20 or 40 t ha−1 can enhance cotton lint and seed yields under rainfed conditions. These improved yields with biochar did not produce increased net returns due to the increased production costs. Many lint quality parameters were unaffected except for micronaire, fiber strength and fiber length. However, potential long-term benefits of enhanced cotton production from biochar application beyond the length of the study merit further investigation. Additionally, biochar application is more relevant when accrued carbon credits through carbon sequestration outweigh the increased production costs due to biochar application.

Pulsed drip irrigation increases growth and production of northern highbush blueberry and floricane-fruiting red raspberry on loam or silt loam soils

Pulsed drip irrigation increases growth and production of northern highbush blueberry and floricane-fruiting red raspberry on loam or silt loam soils

Soil hydraulic properties and field-scale hydrology as affected by land-management options

Recurring puddling for long-term rice cultivation forms a plow pan at a particular soil depth, which alters soil hydraulic properties, field-scale hydrology, and nutrient persistence in the soil. This experiment aimed to assess the impact of long-term rice cultivation on root-zone soil hydraulic properties and field-scale hydrology. Soil core samples were collected from four land management options namely, rice‒rice, non-rice, rice and non-rice, and field ridge, at two sites, one with loam and another with silt-loam soil. The soil cores were sampled for each 10 cm layer up to 100 cm depth from three locations of each rotation at both sites. Soil hydraulic parameters were estimated using a pedotransfer function based on the measured bulk density and soil texture. A mathematical model named HYDRUS-1D predicted infiltration, percolation, and surface runoff with the estimated hydraulic properties for three extreme rainfall events, i.e., 3.33, 5, and 6.66 cm hr&lt;sup&gt;-1&lt;/sup&gt;, during a 3-hour period. A plow pan was found at 20–30 cm soil depth for all the land management options but not for the field ridge. The plow pan of the rice‒rice rotation had the highest bulk density (1.53 g cm&lt;sup&gt;-3&lt;/sup&gt;) and the lowest hydraulic conductivity (17.56 cm day&lt;sup&gt;-1&lt;/sup&gt;). However, the top 10 cm soil layer in the rice–rice field had the lowest bulk density (0.93 g cm&lt;sup&gt;-3&lt;/sup&gt;). At both sites, the field ridge had higher infiltration and percolation and lower runoff than other rotations. The study reveals that the field-ridge area of a rice field can be the main water loss pathway. Phosphorus concentration in the rice-rice rotation decreased from 7.7 mg kg&lt;sup&gt;-1&lt;/sup&gt; in the 10-cm soil layer to 2.49 mg kg&lt;sup&gt;-1&lt;/sup&gt; in the 100-cm layer. These findings will facilitate making better water management decisions.

Corrosion of carbon steel in artificial soil: Processes occurring during wet/dry transitions studied with a multi-coupon electrode

A multi-coupon electrode, composed of 16 square (5 mm × 5 mm) carbon steel coupons, was buried at room temperature during 125 days in an artificial silt loam soil. The soil was initially set at 75% of the saturation with a 0.01 M NaCl + 0.01 M NaHCO3 solution in a specific electrochemical cell. The experimental cell was hermetically closed for 32 days before to be opened so that the effects induced by the progressive drying of the soil could be studied. The OCP and the soil electrolyte resistance Rs, determined by electrochemical impedance spectroscopy, were then monitored over time for each coupon. During the drying process, different behaviors were observed for the various coupons, demonstrating the heterogeneity of this process. XRD analysis of the corrosion product layer covering each coupon at the end of the experiment revealed significant variations of composition from one coupon to another. The composition of the corrosion product layers could be interpreted in link with the OCP and Rs measured values.

Nutrient Leaching Losses from Continuous Application of Washed Rice Water on Three Contrasting Soil Textures

Washed rice water (WRW) is often used as liquid plant fertilizer. However, there is no study on nutrient leaching of soils due to frequent WRW application. Therefore, a column study was undertaken to evaluate the rate of nutrient leaching losses, nutrient retention, and recovery of elements in leachates of three different soil textures irrigated with WRW. The treatments were 3 soil textures and 2 water types. The treatments were evaluated for 8 weeks, and the soils and leachates were measured biweekly. Factorial and repeated measurements in a completely randomized design were therefore employed. Higher cumulative leaching of the elements was found in sandy clay loam soil with 666.29, 378.13, 138.51, 50.82, 44.61, and 27.30 mg L-1 of K, P, Mg, Ca, NH4+-N, and NO3--N, respectively. Higher percentages of elements recovery in leachate were found in the sandy clay loam soil with a range of increase by 37.8–283.1% than the other two soil textures. In contrast, after 8 weeks of WRW application, the clay and silt loam soils had a range of increase in nutrient retention by 0.43–1358.5% than the sandy clay loam, with P and NO3--N being the highest and the lowest elements retained, respectively, for all soil textures. This study showed that frequent WRW disposal on sandy textured soils risks higher environmental contamination, mainly due to the soil’s lower water retention and nutrients, leading to nutrient leaching. Therefore, organic amendments should be added to sandy textured soils.