Soil Permeability Research Articles

Impact of irrigation, fertilizer, and pesticide management practices on groundwater and soil health in the rice-wheat cropping system-a comparison of conventional, resource conservation technologies and conservation agriculture.

Agricultural intensification in the Northwestern Indo-Gangetic Plain (NWIGP), a critical food bowl supporting millions of people, is leading to groundwater depletion and soil health degradation. This is primarily driven by conventional cultivation practices in the rice-wheat (RW) cropping system, which dominates over 85% of the IGP. Therefore, this study presents a systematic literature review of input management in the RW system, analyzes district-wise trends, outlines the current status, identifies problems, and proposes sustainable management options to achieve development goals. Our district-wise analysis estimates potential water savings from 20 to 60% by transitioning from flood to drip, sprinkler, laser land leveling, or conservation agriculture (CA). Alongside integrating water-saving technologies with CA, crop switching and recharge infrastructure enhancements are needed for groundwater sustainability. Furthermore, non-adherence with recommended fertilizer and pesticide practices, coupled with residue burning, adversely affects soil health and water quality. CA practices have demonstrated substantial benefits, including increased soil permeability (up to 51%), improved organic carbon content (up to 38%), higher nitrifying bacteria populations (up to 73%), enhanced dehydrogenase activities (up to 70%), and increased arbuscular mycorrhizal fungi populations (up to 56%). The detection of multiple fertilizers and pesticides in groundwater underscores the need for legislative measures and the promotion of sustainable farming practices similar to European Union strategies. Lastly, emphasis should be placed on fostering shifts in farmers' perceptions toward optimizing input utilization. The policy implications of this study extend beyond the NWIGP region to the entire country, stressing the critical importance of proactive measures to increase environmental sustainability.

Phosphorus transport in a hotter and drier climate: in-channel release of legacy phosphorus during summer low-flow conditions

Abstract. “Legacy phosphorus” is the historical accumulation of phosphorus (P) in soils and sediments due to past human inputs. River networks represent a potential sink and/or source of legacy P, with many in-channel processes potentially governing the storage and mobilization of P over time. The objective of this study was to evaluate the potential contribution of the in-channel release of legacy P to bioavailable P transport in streams during summer low-flow conditions across a land use gradient in Minnesota, USA. We addressed this objective through the synthesis of (1) water quality and streamflow (Q) data collected for 143 gauged watersheds across the state of Minnesota between 2007–2021 (22 750 total samples); (2) water quality data from 33 additional ditch, stream, and river sites in Minnesota sampled under low-flow conditions in the summer of 2014; and (3) water quality data collected from tile drainage outlets for 10 monitored farm fields between 2011–2021. We used geospatial data and a random forest modeling approach to identify possible drivers of bioavailable P concentrations during summer low flows for gauged watersheds. During low flows in late summer, between one-third to one-half of the gauged watersheds we studied exhibited soluble reactive phosphorus (SRP) concentrations that were above previously identified thresholds for eutrophication of 0.02–0.04 mg L−1. For many of these watersheds, stream SRP concentrations in late summer were above those observed in tile drainage outlets. Elevated SRP concentrations during late-summer low flows weakened concentration–discharge relationships that would otherwise appear to indicate more strongly mobilizing SRP–Q responses across other seasons and flow conditions. While wastewater discharge likely contributed to elevated P concentrations for watersheds with high densities of treatment plants, many watersheds did not have substantial wastewater impacts. The most important variables for predicting bioavailable P concentrations during late-summer low-flow conditions in a random forest model were land use in riparian areas (particularly crop cover); soil characteristics including soil erodibility, soil permeability, and soil clay content; agricultural intensity (reflected via higher pesticide use, higher phosphorus uptake by crops, and higher fertilizer application rates); watershed precipitation; and stream temperature. These findings suggest that, for stream and river sites heavily impacted by past and current P inputs associated with agriculture and urbanization, biogeochemical processes mediated by climate and geology can result in the release of legacy P from in-channel stores during late-summer low-flow conditions. As summers become hotter and, at times, drier – which are predicted changes in this region – conditions for the release of legacy P stored in stream and river channels will likely become more prolonged and/or more acute, increasing eutrophication risk.

Yield Impact of Data-Informed Surface Drainage: An On-Farm Case Study

Drainage is an important aspect of effective water management in row-crop agriculture. Drainage systems can be broadly categorized as either subsurface or surface drainage. A significant amount of design goes into subsurface drainage installations, such as tile networks, and permanent surface drainage installations, such as waterways and berms. However, many farmers also implement temporary surface drainage installations to drain localized areas within their fields each year. This practice involves creating shallow water paths, typically using spinner ditchers, and it is especially commonplace in areas with poor soil permeability. However, this practice is traditionally performed using only observations by farmers and without any data-based workflows. The objective of this study was to analyze the potential yield benefits from a more data-informed approach to surface drainage on a production row-crop farm by exploring corn and soybean yield data from 2008–2021 from two fields where a data-informed approach to surface drainage was implemented. Field topography and drainage information were combined with yield maps from prior years with traditional ad hoc drainage and the years following the incorporation of the data-informed approach to better understand the impact of the workflow. Geospatial distribution of the average normalized crop yields and elevation maps for the fields were analyzed to isolate the yield impacts of the areas affected by the data-informed on-farm surface drainage artifacts. In the years after implementation of the data-informed surface drainage approach, Field 1 and Field 2 showed respective increases of 18.3% and 13.9% in average corn yields. Further analysis isolating three areas affected by the surface drainage using topography and drainage layout showed that all three isolated areas improved more than the field averages, ranging from 15.9–26.5% for Field 1 and 21.4–40.2% for Field 2. Similarly, soybean yields were also higher in the isolated affected areas after the data-informed drainage ditch construction. The findings highlight the effectiveness of data-informed on-farm surface drainage, a relatively straightforward approach that proved beneficial for both soybean and corn production.

Enhancing accurate prediction of soil permeability coefficients using data-driven approaches for soil and water conservation

Enhancing accurate prediction of soil permeability coefficients using data-driven approaches for soil and water conservation

Physics-based time-of-failure determination of rainfall-induced instability in lateritic soil slopes

Conventional time-of-failure estimated from slope surface displacement over time, ignores the crucial geotechnical and environmental causative factors that lead to slope instability. The instrumentation and monitoring are expensive, labour-intensive, and often not feasible for large number of hill slopes. This paper focuses on the physics-based determination of time-of-failure charts for laterite soil slopes prevalent in the Western Ghats of India, under rainfall infiltration. The finite element model was first validated by performing coupled flow deformation analysis of Kondavi soil cutting situated in the Ratnagiri district of Maharashtra, India. The soil samples were collected from the site for basic geotechnical characterisation in the laboratory. In addition, the soil water characteristics curve (SWCC) was determined using the filter paper method, and the unsaturated parameters were obtained using the van Genuchten model. Following the validation of numerical model with the failed Kondavi cutting, the factor of safety (FOS) and time-of-failure (TOF) were studied for varying rainfall intensity, and permeability of the soil. The FOS and TOF charts were then established for varying slope angles (30°, 45°, 60°), effective cohesion (10 kPa, 18 kPa, 25 kPa), effective friction angle (22°, 25°, 28°), water table depth (25 m, 28 m, 30 m, 35 m) and height of slope (15 m, 25 m, 35 m). Results indicate that if rainfall intensity is lower than soil permeability, TOF depends on both the intensity and duration of the rainfall. Higher rainfall intensity leads to a shorter time of failure, and vice versa. Conversely, when rainfall intensity exceeds soil permeability, TOF is determined by the duration of rainfall and the permeability of soil, as the rainfall infiltrates at the saturated permeability rate regardless of its intensity. It is also observed that friction is the dominant parameter for initial FOS, while cohesion is the dominant parameter for the TOF of a rainfall-induced landslide. Finally, charts are proposed that shall serve as a preliminary guide for the determination of the TOF for rainfall-induced instability in the lateritic soil slopes of India. The performance of the charts is further evaluated by comparing the observed and predicted TOF of two other failed laterite cuttings. The implications of these findings are profound, as the proposed TOF charts can be integrated into early warning systems, contributing towards improved disaster mitigation and preparedness with timely decision making for adequate management of landslide associated risks.

Steady infiltration rate: Relation to antecedent soil moisture, soil permeability, and measurement method and period

ABSTRACT Soil steady water infiltration rate (SIR) is a key variable in hydrological modeling, but its relationship to antecedent soil moisture is not yet well understood. We tested the hypothesis that the SIR decreases with the increase in antecedent moisture, and that this relationship depends on permeability to water on the soil surface, the measurement method, and the measurement period. We conducted an experiment in an Argissolo Vermelho-Amarelo Distrófico abrúptico (Psammentic Paleudult – Soil Taxonomy), measuring infiltration in up to 14 antecedent moisture conditions under two soil structural conditions (no-till and no-till with subsoiling), with two measurement methods (double ring and Cornell infiltrometers), and for up to 48 h, with ten replications. In addition, vertical effective hydraulic conductivity of the saturated profile (Kef) was determined with Darcy’s equation for N layers. Crop succession used in the area was black oats and ryegrass in the winter and soybean in the summer. The SIR decreased to as little as 7.7 % of its original value with the increase in antecedent moisture; it was ~200 % greater in the treatment with subsoiling compared to no-till alone, and ~80 % greater when measured with the Cornell infiltrometer than with the double ring infiltrometer. Nevertheless, the effects of the method and the soil structural condition declined with the increase in antecedent moisture, confirming our hypothesis. In soil initially nearly saturated (degree of saturation ~90 %), the SIR drew near Kef (12.7 mm h -1 ) under the two soil structural conditions, especially when measured with the double ring infiltrometer. In contrast, increasing the time for measuring infiltration (>2 h) did not generate a new lower SIR level. The SIR decreases with the increase in antecedent soil moisture, and this relationship depends on the permeability to water of the surface layers and the measurement method. The SIR determined with infiltrometers better corresponds to vertical infiltration the nearer the soil is to saturation before beginning measurement.

Profitability and environmental implications of innovative practice changes and irrigation improvements

The economic and environmental benefits of practice changes and irrigation improvements are explored based on three grower case studies in the Bundaberg, Burdekin and Mackay regions that consider grower investments in best management practices, including irrigation changes. How the practice changes influenced farm economic and environmental performance are determined. Economic, biophysical and farm management data before and after the changes were used to calculate the economic benefit (Annualised Equivalent Benefit) with the Farm Economic Analysis Tool (FEAT) and an investment analysis. The economic benefit was positive for all farms, ranging from AUD29 to AUD377 per hectare per year. The same data were used to calculate indicators of environmental performance (per tonne of harvested cane) using the Cane Life Cycle Assessment (CaneLCA) tool. There were reductions in fossil-fuel use, greenhouse-gas emissions, and a potential for water pollution curtailment. For the Bundaberg case, a transition from furrow to low-pressure boom irrigation increased electricity use, which was offset by energy savings from other aspects of the production system changes. For the Burdekin case, improved water-use efficiency on a farm with permeable soils resulted in less electricity use and greenhouse gas emissions. For the Mackay case, improved utilisation of water allocation increased cane productivity and contributed to improved economic and eco-efficiency outcomes. While total water use increased, it is noted that water availability is not a constraint for the Mackay region outside of drought impacts. The Mackay case also involved a supplementary analysis of solar energy use. Overall, the case studies showed that the suites of irrigation improvements and practice changes resulted in both economic and eco-efficiency benefits.

Effects of initial water and salt content on permeability and microstructure of sodic-saline loessal soils

Effects of initial water and salt content on permeability and microstructure of sodic-saline loessal soils

Impact of Land Use Conversion on Soil Structure and Hydropedological Functions in an Arid Region

ABSTRACTLand use conversion critically affects soil structure and associated functions. This study investigated variations in soil structure and hydropedological characteristics across different land use types, that is, uncultivated, cultivated, and abandoned land under an arid condition. Water‐stable aggregates in the uncultivated land were 15.4%–37.1% of those in the cultivated and abandoned lands at depths of 0–60 cm. Reclamation of the uncultivated land enhanced soil aggregate stability, while prolonged tillage led to the loss of binding organic matter, breakdown of large aggregates and decrease in aggregate stability. The mean weight diameter of aggregates at 0–40 cm depth in the cultivated land was 39.0% lower than in the abandoned land. The volume fraction of micropores (< 100 μm) in the cultivated soils was 3.7%–39.7% of that in the uncultivated soils, whereas macropores (> 1000 μm) was 1.4–1.8 times greater. Following the abandonment, soil pore diversity recovered and a hierarchical structure developed. In the abandoned land, the volume fraction of micropores (< 100 μm) was 2.4–18.9 times that of the cultivated lands, while macropores (> 1000 μm) constituted 81.4%–93.9% of those in the cultivated lands. The permeability and longitudinal dispersivity of soils in the cultivated land were significantly lower than in the uncultivated and abandoned lands, particularly at deeper soil layers. The increase in large pores in the abandoned land, important for water movement and solute transport, resulted in an order‐of‐magnitude rise in both permeability and longitudinal dispersivity compared with the cultivated lands. Overall, the abandoned land showed potential for rehabilitation from the perspectives of soil aggregates and pore structure. The findings may provide reference for land reclamation and management in arid regions.

Preliminary results of spatial distribution of radon and thoron with associated parameters in soil around active faults in Japan.

The radon (Rn) and thoron (Tn) concentrations and other environmental parameters were measured in the vicinity of active faults in two regions with different geology structure of Japan. The range of measured values was from 1.2 to 74 kBq m$^{-3}$, 1.1 to 38.9 kBq m$^{-3}$, 0% to 4.35%, and 2$\times $10$^{-13}$ to 4$\times $10$^{-11}$ m$^{2}$, for Rn, Tn, CO$_{2}$, and soil permeability, respectively. Significant differences in the measured parameters were observed, suggesting that Rn concentrations near faults are strongly influenced by geological structure and fault type. Based on statistical analysis, good correlations were found between Rn, Tn, and CO$_{2}$ (carried gas ) concentrations. It is planned to continue the study with measurements at a number of additional sites.

Monitoring soil salinization and waterlogging in the northeastern Nile Delta linked to shallow saline groundwater and irrigation water quality

Soil salinization and waterlogging are critical environmental issues affecting agricultural productivity and cultural heritage preservation, particularly in arid regions. This study investigated soil degradation processes in the archaeologically and agriculturally significant northeastern Nile Delta of Egypt. The objective was to assess the severity of soil degradation and identify key drivers related to water resources and soil characteristics to aid in the development of management strategies. The research employed a multi-faceted approach, including hydrochemical analyses (of groundwater, irrigation water, and soil), water quality indices calculations, statistical analyses, and satellite data. The results revealed high levels of soil salinization in the northern and central areas, with 64% of soil samples classified as strongly and very strongly saline. Soil chemistry indicated salinization sources linked to sodium chloride dominance. Satellite data from Sentinel-2 images and SRTM digital elevation data showed widespread severe waterlogging in the northern lowlands. The Irrigation Water Quality Index (IWQI) values indicated that 87.5% of irrigation water samples posed severe restrictions due to high salinity and sodium hazards, which were mismatched with the low soil permeability observed in 81% of the collected samples exhibiting clay texture and covering most of the study area. Furthermore, shallow groundwater at depths of 0.5–3 m with high salinity was detected, where total dissolved solids exceeded 20,000 mg/L, and Na-Cl water types prevailed, indicating saltwater intrusion. A strong positive correlation (r > 0.83) was found between shallow saline groundwater and soil salinity. The combination of poor irrigation water quality, shallow saline groundwater tables, and low-permeability soils created a synergistic effect that severely compromised soil health and agricultural productivity. It also posed severe risks to the structural integrity of archaeological sites and buried artifacts through accelerated physical and chemical weathering processes. This necessitates an urgent mitigation strategy to combat soil degradation in this critical area.

Evaluation of the Impact of Recycled Distillery Effluent on the Cultivation of Wheat and Sorghum

With increasing global water scarcity, the reuse of treated wastewater for agricultural irrigation offers a promising solution, particularly in arid regions. This study evaluates the impact of distillery wastewater from Kinmen Kaoliang Liquor Inc. (KKL) on the growth of wheat and sorghum in the Kinmen region. The field experiment applied varying proportions of KKL wastewater to assess its effects on soil properties, nutrient distribution, and crop performance. The results showed that wastewater irrigation increased soil concentrations of key nutrients, such as potassium (K), sodium (Na), magnesium (Mg), and phosphorus (P), but also raised the electrical conductivity (EC) and sodium adsorption ratio (SAR) beyond acceptable irrigation standards. K, Mg, Ca, and P primarily accumulated in the stems and grains, while Na was concentrated in the roots. However, higher wastewater concentrations negatively affected soil permeability due to Na accumulation, and elevated salinity levels led to reduced plant biomass. This study concludes that although wastewater irrigation improves nutrient availability, careful management is essential to mitigate salinity risks and ensure sustainable agricultural practices. These findings offer valuable insights into the potential of wastewater reuse in water-scarce regions and provide practical recommendations for managing associated risks.

Snowmelt-mediated isotopic homogenization of shallow till soil

Abstract. The hydrological cycle of sub-arctic areas is dominated by the snowmelt event. An understanding of the mechanisms that control water fluxes during high-volume infiltration events in sub-arctic till soils is needed to assess how future changes in the timing and magnitude of snowmelt can affect soil water storage dynamics. We conducted a tracer experiment in which deuterated water was used to irrigate a plot on a forested hilltop in Lapland, tracked water fluxes of different mobility and monitored how the later snowmelt modifies the labelled soil water storage. We used lysimeters and destructive soil coring for soil water sampling and monitored and sampled the groundwater. Large spatiotemporal variability between the waters of different mobility was observed in the subsurface, while surface water flow during the tracer experiment was largely controlled by a fill-and-spill mechanism. Extensive soil saturation induced the flow of labelled water into the roots of nearby trees. We found that labelled water remained in deeper soil layers over the winter, but the snowmelt event gradually displaced all deuterated water and fully homogenized all water fluxes at the soil–vegetation interface. The conditions required for the full displacement of the old soil water occur only during a snowmelt with a persistently high groundwater table. We propose a conceptual model where infiltration into the soil and eventual soil water replenishment occur in three stages. First, unsaturated macropore flow is initiated via the surface microtopography and is directed towards the groundwater storage. The second stage is characterized by groundwater rise through the macropore network, subsequent pore water saturation and increased horizontal connectivity of macropores. Shallow subsurface lateral fluxes develop in more permeable shallow soil layers. In the third stage, which materializes during a long period with a high groundwater table and high hydrological connectivity within the soil, the soil water is replenished via enhanced matrix flow and pore water exchange with the macropore network.

Hydraulic properties for a wide range of undisturbed and compacted French forest soils: in situ measurements and estimation with the BEST method

Key messageThe dataset provides hydraulic properties estimated using the Beerkan Estimation of Soil Transfer (BEST) method, on undisturbed and on compacted and rutted French forest soils. It allows a reliable assessment of the effect of traffic on soil permeability. However, hydraulic properties could not be estimated on extremely rutted soils, underscoring the necessity for tailored protocols for these conditions.

An Urban Lake Drainage Catena: Influences of Terrain, Soils, and Precipitation

Urban lake drainage systems are heavily impacted by terrain, soil characteristics, and precipitation, which influence water infiltration and groundwater movement. This study focused on the drainage catena around Lake Nokomis in Minneapolis, Minnesota, where local residents have experienced wet basements and yards. The primary goal was to identify the factors contributing to these water-related problems, particularly soil permeability and how it responds to precipitation. By conducting soil borings, using pressure transducers, and measuring saturated hydraulic conductivity (Kfs), the study compared upland and lowland areas. Findings indicated that upland soils, primarily composed of sandy fill, had much higher infiltration rates, with Kfs values ranging from 72.4 cm/hr to 149 cm/hr. In contrast, lowland areas characterized by lacustrine and organic soils exhibited significantly lower Kfs values, ranging from 1 cm/hr to 14.8 cm/hr. Between 2022 and 2024, wet and dry seasons occurred, yet recorded more than 127.5 cm of rain and snow water equivalent, further contributing to groundwater rise and surface water presence in low-lying regions. The study concluded that increased precipitation, coupled with specific hydrogeologic conditions, was the main factor causing elevated groundwater levels and surface saturation in these areas. To address these challenges, Minnesota's water management authorities are encouraged to implement strategies that consider the increasing magnitude and intensity of precipitation events due to climate change. Incorporating hydrogeologic assessments into urban planning is recommended to better manage water infiltration, reduce flood risks, and strengthen the resilience of drainage systems to changing climate patterns.

The Effects of Bedrock Topography and Soil Permeability on Saturated Zone Distribution in a Mountainous Steep‐Slope Area

ABSTRACTSaturation development and distribution at the soil–bedrock interface are important for predicting shallow landslide occurrence. Previous studies have indicated that saturation is generated in bedrock depressions and valleys and that bedrock groundwater seepage generates locally saturated areas. However, the effects of soil permeability, which is known to be heterogeneously distributed, on saturation development and distribution are poorly understood. In this study, we performed unprecedented high‐resolution (approximately 50 cm grid) soil pore water pressure and soil temperature monitoring using 141 tensiometer–thermocouple sets in a plot measuring approximately 5 × 4 m to investigate the effects of topography and bedrock groundwater seepage on saturation development and distribution. We then measured permeability distribution of two soil profiles, including at the soil–bedrock interface, using the Guelph Permeameter method (GP method) for comparison with saturated zone distribution and saturation duration. The results indicated that a perennial saturated area was formed by bedrock groundwater seepage and was distributed downstream from a certain bedrock surface altitude in the lower region of the study plot. After a peak of rainfall, the perennial saturated area expanded upslope owing to the increased seepage. In areas without the influence of bedrock groundwater, saturation was observed to retreat rapidly at high permeability points and persist over long periods at low permeability points; however, the saturation duration was inconsistent with the bedrock surface topography. Therefore, it is suggested that the bedrock altitude controls the saturation distribution generated by bedrock groundwater, whereas the distribution of saturation that is associated with direct rainwater infiltration may be controlled by the permeability distribution during recession periods. Although the plot size was small, the unprecedented high‐resolution observations suggest that the permeability distribution, rather than the bedrock topography, may control the saturated zone distribution following rainfall.

Measurements of Drying and Wetting Gas Diffusion Coefficients and Gas Permeability of Unsaturated Soils Using a New Flexible-Wall Device

Measurements of Drying and Wetting Gas Diffusion Coefficients and Gas Permeability of Unsaturated Soils Using a New Flexible-Wall Device

Grassland woody encroachment alters subsurface mineral weathering and groundwater composition in a carbonate system

Displacement of grasses by woody plants (woody encroachment) is occurring in grasslands worldwide. Previous studies indicate that encroachment can alter subsurface carbon dioxide (CO2) concentrations and mineral weathering, though these impacts are still poorly understood. To address this knowledge gap, we sampled groundwater and stream water every three weeks during the 2022 water year from two watersheds at Konza Prairie Biological Station, a native tallgrass prairie underlain by limestone and mudrock units in Kansas, USA. Amounts of woody encroachment differ between the watersheds primarily because of differences in fire frequency. One watershed is burned annually and contains 6 % and 45 % woody plant coverage in its upland and riparian areas, respectively, whereas the other is burned every four years and contains 28 % and 74 % woody plant coverage, respectively. We expected to find higher CO2 levels in the more encroached watershed, assuming the deep roots of woody plants increase inputs of CO2 to bedrock. However, we found the opposite. Our results indicate that groundwater from a single limestone aquifer contained an average of 1.4 mM CO2 in the less encroached watershed and 1.0 mM CO2 in the more encroached watershed. Similarly, stream water CO2 concentrations at the outlet of the less encroached watershed (0.25 mM) were more than twice that of the more encroached watershed (0.12 mM) on average. Despite these differences in CO2 concentration, amounts of mineral weathering per liter of groundwater differed little between watersheds. We hypothesize that encroachment is causing differences in CO2 concentrations between watersheds by decreasing the proportion of mineral weathering that occurs under conditions that are open with respect to CO2 exchange. During open-system weathering, dissolved CO2 consumed by weathering reactions can be replaced from an adjacent gas phase, allowing CO2 concentrations to remain elevated as weathering progresses. In contrast, during closed-system weathering, CO2 is not replaced and decreases in concentration as weathering progresses. If weathering primarily occurs under open-system conditions within the study area soils, which are unsaturated, and closed-system conditions within the underlying bedrock, where pores are more commonly saturated, then woody encroachment has the potential to decrease the proportion of open-system weathering by increasing soil permeability and thus decreasing soil water residence times. This hypothesis is consistent with our findings and implies that a shortening of soil water residence time with woody encroachment lowers the proportion of CO2 delivered from the soil to the subsurface and creates a more aggressive weathering engine at depth and along deeper flow paths. Encroachment may also be altering soil CO2 production and/or venting, though these possibilities require further investigation.

Modelling Seasonal Variability in Parameters Defining Volumetric Water Content in a Low Permeability Soil in Central Illinois: An Application of MODFLOW‐6 and the Unsaturated Zone Flow Package

ABSTRACTIncreasing interest in solute transport phenomena in agricultural systems on a sub‐annual basis necessitates a better understanding of seasonal changes in natural systems and how these changes can be incorporated into modelling. A better understanding of the seasonal timing of nutrient loading in tile drained agricultural systems in particular is essential for efforts trying to replicate or predict the occurrence of harmful algal blooms. Literature exists showing there are seasonal dynamics (freeze–thaw, plant‐root processes, land management practices, etc.) that may cause changes in the hydraulic properties of the soil zone including hydraulic conductivity and porosity. To test whether these changes are important in an agricultural system, a MODFLOW‐6 model using the unsaturated zone flow package was constructed. The simulation was comprised of separate, seasonal models to be run sequentially with each year being broken into a winter and summer seasons. As part of this architecture, model parameters representing soil hydraulic properties were allowed to vary by season. The model was calibrated against soil moisture observations at multiple depths using a genetic algorithm machine learning technique. The parameters of the sub‐models were compared for the winter and summer seasons. Brook‐Corey epsilon, saturated vertical conductivity, saturated volumetric water content and residual volumetric water content were found to be consistently different between the modelled summer and winter periods. A more traditional model which did not allow hydraulic properties to vary seasonally was also run and compared to the seasonal architecture and the seasonal architecture was found to improve simulation results. The hydrologic dynamics of the unsaturated zone—particularly in tile drained agricultural systems—control the residence time for water and solutes, which is critical for in‐field chemical processes such as denitrification. This work has important implications for seasonal transport phenomena in agricultural systems and improving the simulation and prediction of harmful algal blooms.

Influence of Trenchless Subsurface Drainage with a Rice Husk Filling System on Soybean Productivity Under a Poorly Drained Paddy Field for Future Applications in Smart Agriculture

In South Korea, paddy fields are increasingly being planted with soybeans to address rice supply and demand issues and increase soybean self-sufficiency. The field crops cannot grow healthily without adequate drainage due to the paddy fields storing water easily. In this study, we identified that Rice Husk Filling Drainage Method (RHDM) technology improved soil permeability and soil aeration. We also found that the soil moisture content was reduced and the water table remained at a lower level in the RHDM plot as compared to the control plot. The soybean moisture stress index showed that in the RHDM plot, the safety standard for stress due to excessive moisture at the 2 m interval was met. The soybean yield was increased by up to 35% in the 2 m RHDM construction interval compared to the control plot. In addition, the high hydraulic conductivity of the rice husk used as the hydrophobic material confirmed sufficient drainage performance and was considered economically advantageous. Therefore, our results show that RHDM is a highly efficient and economical drainage method in poorly drained paddy soils. Drainage management is essential for stable crop production in poorly drained paddy fields. Our research findings suggest that an efficient open field water management method is viable, which we believe will lead to future advances in open field smart agriculture.