Saturated Hydraulic Conductivity Research Articles

Three-dimensional X-ray imaging of macropore flow

Macropores are known to be important pathways for the rapid transport of water, solutes and colloids in soil. Nevertheless, we still know very little about how the topology and geometry of macropore networks govern water flow configurations and velocities in natural soil. In this study, we aimed at gaining more insight into macropore flow by using X-ray tomography to quantify air–water distributions in the macropore networks of undisturbed topsoil and subsoil columns of a clay soil at varying steady-state flow rates. We observed that while large fractions of the macropore network remained air-filled, the air phase only became entrapped when the irrigation rate was very close to the saturated hydraulic conductivity of the soil. The data enabled us to parameterize a kinematic wave model for water flow following the approach proposed in Jarvis et al. (2017a). Follow-up experiments would be required to evaluate whether these kinematic wave parameters derived by X-ray imaging match with those obtained from outflow measurements. We found that quantitative X-ray imaging of macropore flow through soils still remains a challenging task. We recommend that future experiments are conducted on smaller soil samples to improve image resolution and minimize experimental time spans as well as X-ray image noise and illumination bias. Such experiments could also include 3-D tracer imaging to identify the imaged macropore networks transporting most of the water (i.e. the backbone) at varying steady irrigation rates.

Assessment and development of pedotransfer functions to estimate soil saturated hydraulic conductivity in arid soils with application to GIS mapping in the Al-Ahsa Oasis, Saudi Arabia

Assessment and development of pedotransfer functions to estimate soil saturated hydraulic conductivity in arid soils with application to GIS mapping in the Al-Ahsa Oasis, Saudi Arabia

Assimilating Seismic Data And Soil Basic Information to Predict Near-surface Permeability And Water Content

Soil permeability plays a key role in the study of earth sciences for agriculture and forestry. Because the traditional laboratory measurement is time-consuming and laborious, and only discrete profile data can be obtained. In this paper, a simple and efficient method using soil transfer function (PTFs), is proposed to estimate permeability and other parameters indirectly by seismic wave observation. Based on Biot’s theory establishing the relationship between shear-wave velocity and permeability, and the basic soil information in the study area, including land survey, logging and drilling data, using the PTFs constraint to estimate saturated hydraulic conductivity, soil components, saturated water content and residual water content may favor the physical corrections of the PTFs. The results show that there are three distinct layers of permeability in the study area, consistent with the velocity structure. The measured basic information further verifies the accuracy of the saturated permeability coefficient estimation, which shows the reliability of the improved PTFs. The established near surface permeability estimation method by integrating seismic wave observation and soil basic information may provide further assimilation for parameter estimation combining geophysical observation and hydrogeographic statistics.

The rainfall threshold of forest cover for regulating extreme floods in mountainous catchments

Floods frequently occur in mountainous regions and threaten lives and property worldwide. Forest cover usually plays an important role in regulating and preventing floods. However, the rainfall thresholds for forest cover to effectively regulate extreme flood are still unclear. In this study, we developed the topography-based subsurface storm flow hydrological (Top-SSF) model, which generally exhibited precise simulation performances in five typical mountainous catchments in southwest China. Then, the Top-SSF model was combined with a frequency analysis method to set different forest cover scenarios, investigating the relationship between rainfall threshold and forest cover in mountainous catchments. The results showed that under the control of soil saturated hydraulic conductivity (Ks) and maximum soil water storage capacity (Szm), the rainfall threshold of an extreme flood (the 100-year return period) increased significantly, especially when forest cover was larger than 70% of a catchment. Under the same forest cover, high initial soil water content (Swi) weakened the mitigating effect of forest cover on the extreme flood. In addition, a non-linear regression relationship between forest cover and rainfall threshold of a catchment was developed considering the impacts of Ks, Swi and annual mean precipitation (P¯) of the catchment. The significant impact of forest cover change on extreme floods was not only due to changing the amount of forest cover but also the soil properties. These results contribute to the understanding of the impact of forest cover changes on extreme floods and may provide valuable insights for flood defence in mountainous catchments.

Magnetically treated water drip irrigation combined with carboxymethyl cellulose (CMC) application: A regulating strategy for enhancing the jujube yield and quality in southern Xinjiang of China

Developing effective regulation strategies for improving the efficiency of irrigation water and fertilizers, and preventing further expansion of desertification in southern Xinjiang, China, is crucial. Magnetically treated water (MTW) has been shown to have a positive effect on plant growth. The carboxymethyl cellulose (CMC) has been widely used as an efficient soil amendment to improve soil aggregation and hydraulic properties. This study aimed to explore the optimal mode of combining MTW drip irrigation and CMC application for high-quality jujube production. Conventional freshwater irrigation was set up in both 2021 and 2022 (control group, CK). CMC treatments under MTW drip irrigation included C0 (0), C150 (150 kg/ha), C250 (250 kg/ha), C350 (350 kg/ha), and C450 (450 kg/ha) in 2021, and C0 (0), C150 (150 kg/ha), C300 (300 kg/ha), C450 (450 kg/ha), and C600 (600 kg/ha) in 2022. The results showed that CMC significantly increased soil porosity, water-holding capacity, and decreased soil bulk density and soil saturated hydraulic conductivity. CMC contributed 2.88 % to 27.96 % of large aggregates (>0.25 mm), significantly improving soil aggregate stability. Water and fertilizer (N, P, K) productivity increased by 4.5 % to 11.0 % and 1.9 % to 11.3 %, respectively. Jujube yield increased by 2.75 % to 15.98 %, and MTW increased jujube yield by 3.10 % compared to the CK. The recommended optimal CMC application rate was approximately 430 kg/ha. This mode provides a reliable theoretical reference for jujube industry development and soil desertification improvement in southern Xinjiang, China.

Divergent shift of normal alpine meadow exacerbated soil loss of hillslope alpine meadows based on field experiments

Global climate change and overgrazing are driving shifts in the plant composition of grassland communities, which may profoundly affect the function of grassland ecosystems in regulating runoff and soil erosion. Here, we examined the shift effects of normal hillslope alpine meadow to shrub and severely degraded meadow states on runoff and sediment generation under natural rainfall conditions, and determined the contributions of plant and soil properties changes to soil erodibility, runoff and sediment generation by in situ rainfall experiment and monitoring on the hillslope of Qinghai-Tibetan Plateau. The results showed that normal meadow shift into severely degraded meadow state, mean weight diameter, soil saturated hydraulic conductivity, soil cohesion and soil erodibility K-factor at the topsoil decreased by 70.3%, 73.1%, 80.3% and −13.1%, respectively, and when normal meadows shift into shrub meadow state, they reduced by 49.1%, −1.3%, 49.4%, and −8.3%, respectively. Runoff and soil loss significantly changed by - 40.0% and 177.8% when normal meadow shifted into a severely degraded meadow state, while runoff and soil loss significantly changed by + 65.0% and +77.8% when normal meadow shifted into a shrub meadow state. Our findings highlight that the two divergent shifts both increased soil loss compared to the normal hillslope alpine meadows. Overall, our results indicate that the divergent shifts of normal alpine meadows exacerbated soil erodibility and soil loss of hillslope alpine meadows. These results obtained here offer a novel perspective on the regulation of runoff and soil erosion in the alpine meadow ecosystem.

Combined influence of rotated transverse anisotropy in mechanical parameters and hydraulic conductivity of soils on reliability evaluation of an unsaturated slope under rainfalls

Natural slopes often exhibit tilted stratification with rotated transverse anisotropy in multiple soil properties, including the mechanical (e.g., friction angle φ and cohesion c) and hydraulic properties (e.g., saturated hydraulic conductivity ks). This phenomenon indicates that to achieve an accurate assessment of slope reliability under rainfall infiltration, the anisotropic spatial variation of the shear strength parameters and ks should be incorporated in a combined manner. Thus, this paper discusses the combined influence of rotated transverse anisotropy in the shear strength parameters and ks on the reliability and failure mechanism of an unsaturated slope under rainfalls. It is found that for a slope with tilted stratification, the failure mechanism and reliability estimator are dominantly influenced by the rotated transverse anisotropy in the shear strength parameters, while the influence induced by that in ks is slight. In particular, only incorporating the rotated transverse anisotropy in ks may lead to an incorrect reliability estimator of a slope with tilted stratification. Herein, the reliability index β would be estimated to be dramatically higher, and β of a slope with horizontal bedding would be higher than that of an anti-dip slope, which is inconsistent with the engineering experiences. Nonetheless, the rotated transverse anisotropy in ks should not be ignored in slope reliability assessment, because ignoring the rotated transverse anisotropy in ks would lead to overestimation of the reliability index β, which is adverse to the safety design of a slope.

Influence of intensive cropping of vegetables on physical and hydraulic properties and functions of an Oxisol in the Brazilian Cerrado

The intensification of agricultural systems (e.g., vegetable production) to supply the food demand of the world’s population has increased over the last decades. In Brazil, the largest area of vegetable cropping systems is located in the Oxisols within the Cerrado biome. These areas are characterized by intensive land use and large-scale mechanized agriculture, which may affect the soil physical quality over time. This study aims to understand the effects of vegetable cropping (VG) systems on physical-hydric properties of highly weathered Oxisols. To this end, soil physical properties were assessed in representative VG systems of different ages [15 (VG15), 20 (VG20), and 30 (VG30) years old] and in a native Cerrado vegetation (CV), which was used as a reference of an intact system. Several analyses were conducted, including soil water retention curve, soil bulk density (ρ), soil penetration resistance (PR), saturated hydraulic conductivity (Ksat), disaggregation index, and structural stability index. In addition, a soil physical quality index (SPQI) was developed to assess the effects of soil management on soil functions and ecosystem services in the VG systems evaluated. It was observed that VG systems promoted soil compaction as indicated by the increase in ρ and PR values compared to the CV. This resulted in changes in soil porosity with mesopores being the most affected. The changes in soil porosity reduced Ksat and field capacity, and increased the permanent wilting point, leading to a reduction in available water capacity. The SPQI was reduced by 34, 32, and 43% in VG15, VG20, and VG30, respectively, compared to the CV (0.89). Based on our SPQI, support of root development and resistance to erosion and degradation were the soil functions most affected, regardless of the VG system age. Our results indicate the need to improve the current management used in VG systems to mitigate soil compaction and improve soil physical quality of Oxisols under these systems in the Brazilian Cerrado. This is essential to restore soil functionality and to ensure the sustainable food production of these systems in the long term.

Analysis of Water Volume Required to Reach Steady Flow in the Constant Head Well Permeameter Method

The most common method for in situ measurement of saturated hydraulic conductivity (Ksat) of the vadose zone is the constant head well permeameter method. Our general objective is to provide an empirical method for determining volume of water required for measuring Ksat using this procedure. For one-dimensional infiltration, steady state reaches as time (t) → ∞. For three-dimensional water flow from a cylindrical hole under a constant depth of water, however, steady state reaches rather quickly when a saturated bulb forms around the hole. To reach a quasi-steady state for measuring Ksat, we assume an adequate volume of water is needed to form the saturated bulb around the hole and increase the water content outside of the saturated bulb within a bulb-shaped volume of soil, hereafter, referred to as wetted soil volume. We determined the dimensions of the saturated bulb using the Glover model that is used for calculating Ksat. We then used the values to determine the volume of the saturated and wetted bulbs around the hole. The volume of water needed to reach a quasi-steady state depends on the difference between the soil saturated and antecedent water content (Δθ). Based on our analysis, between 2 and 5 L of water is needed to measure Ksat when Δθ varies between 0.1 and 0.4 m3 m−3, respectively.

Hydraulic and pore functions of differently textured soils modified by biochar from different parts of the mango plant

Studies that elucidate the likely differential impact of biochar produced from different parts of the same plant on soil functions and structure are scanty. Therefore, in this study, biochar made from 2 feedstocks: Mango Twig (B1) and Mango Branch (B2) were pyrolyzed at 550 ○C, and mixed with 2 differently textured substrates (silt loam – S and sandy loam –SD) at application rates of 0%, 3%, 4.5% and 6%, and uniformly prepared to a bulk density (BD) of 1.4 g cm−3. The substrates were subsequently subjected to standard procedures to characterize the affected water retention properties, air permeability, and saturated hydraulic conductivity (Ks). The results indicate marked differences in the impact of biochar types on the available water and water retention capacity, depending on soil texture. The significant main effect of the biochar type on Ks in silty loam and the plant available water capacity in sandy loam highlights the relevance of the selected part of the feedstock pyrolyzed. The optimum amount of biochar required to achieve a significant increase in soil water content was about 3% in both substrates, while air permeability and pore continuity were significantly altered at about 6% biochar amendment rate. Moreover, significant (P < 0.05) improvements in the saturated hydraulic conductivity were observed in the biochar-amended soil compared to the control. Air permeability decreased as the added biochar increased, while the air-filled pores increased at defined matric potential in all treatments. The improvement in soil functions was mostly due to the modification of soil structure parameters (pore size distribution (PSD) and pore continuity), due to increased meso pores concomitant with biochar additions; and greater changes were obtained with B1. The varied impact of the biochar types especially on the soil water retention, available water capacity, pore continuity, and hydraulic properties for the different soil textures showed that even the selected plant part affects the options to improve soil functions.

Impact of roots on the hydrogeological properties of silty soil covers

Mine tailings storage poses significant environmental risks such as the formation of acid mine drainage. Engineered covers offer a solution by controlling water ingress. Their performance is based on specific soil hydrogeological properties (SHPs). They must support vegetation which can impact saturated hydraulic conductivity ( ksat) and water retention curve (WRC). This study assesses the impact of 4-year-old willow root colonization on silty soil covers using flexible wall parameters and water retention tests. The obtained SHPs were compared with root traits. The results suggested that the hydrogeological properties of the studied in situ samples were not significantly affected by roots. The variation of measured and predicted ksat values spanned an order of magnitude, regardless of the root colonization intensity, up to a root length density (RLD) of 2.98 cm/cm3. RLD showed a significant and positive linear relationship with measured ksat values ( R2 = 0.54). However, when root colonization was low (RLD &lt; 1 cm/cm3), RLD was negatively correlated with the nvG ( R2 = 0.44) parameter of the van Genuchten WRC model, while the opposite relationship was observed for samples with RLD &gt; 1 cm/cm3 ( R2 = 0.61). Additionally, RLD and the coarse root (diameter &gt; 1 mm) volume to fine root volume (C/F ratio) influenced WRCs. Over time, coarser roots may have a more pronounced impact on SHPs; further research is needed.

Impact of biochar particle size and feedstock type on hydro-physical properties of sandy soil

Abstract Biochar, as an organic amendment, could positively change soil properties, especially soil with low organic matter and/or poor structure. Biochar application in sandy soil with low organic matter could be an effective tool for improving hydro-physical parameters of the soil economically and ecologically as well. The effect on bulk density, particle density, porosity, saturated hydraulic conductivity and available water content for plants of two biochar types applied at three different particle sizes in a sandy soil was examined. The results confirmed previous studies, showing decreased bulk density, particle density and saturated hydraulic conductivity and partially increased available water content for plants and porosity. Both biochar type and particle size affected the studied soil hydro-physical parameters. After analysis and comparison of two different types of biochar and three particle sizes, the most effective treatment for sandy soil was proved by the biochar produced from willow with the smallest particle size (&lt;125 µm).

Soil Tillage and Cropping System Effects on the Physical-Hydric Properties of a Soil under No-Tillage

A no-tillage system (NT) is an alternative to replace soil management with intense soil tillage and degradation. Our objective was to evaluate the physical–hydric properties of soil under NT for four years after undergoing 13 years of minimum (4NTM) and conventional tillage (4NTC) with reference to continuous NT for 17 years (17NT). The soil bulk density, porosity, storage capacities of water and air, visual evaluation of soil structure (VESS), and saturated hydraulic conductivity were determined. The root dry biomass of soybean, maize, and palisade grass was also measured. NT during four years established after receiving 13 years of tillage did not significantly affect soil properties compared to 17NT, which means that four years of NT reached structural stability similar to continuous 17NT. The VESS scores were less sensitive to identifying soil compaction. Crops have no significative influence on soil properties, but the roots of maize seem to be less sensitive to soil compaction, which is important considering it is in a crop rotation system. The treatments (soil tillage and crop rotation) presented soil compaction below a 10 cm depth, and to our loamy textural class soil, a Bd &gt; 1.60 Mg m−3 restricted soil aeration due to macroporosity &lt; 0.10 m3 m−3.

Spatial variations in soil erodibility induced by rock outcropping on sloping cropland in the karst region of Southwest China

Sloping croplands in karst areas of Southwest China usually contain a multitude of rock outcrops with diameters larger than 25 cm. Rock outcrops and spatial location have substantial effects on soil properties and thus likely affect soil erodibility. Moreover, rock outcropping is a indicator of rocky desertification and has an important impact on soil erosion and soil formation processes. However, the potential effects of spatial location and rock outcrops on the soil erodibility of sloping cropland in karst areas are still unclear. This study was performed to explore the variations in soil erodibility reflected by saturated hydraulic conductivity (KS), mean weight diameter (MWD), soil structural stability (SSI), soil erodibility factor (K) and soil organic carbon content (SOC) at three spatial locations in sloping cropland with rock outcrops on the karst hillside. The results showed that the soil erodibility indicators KS, MWD, SSI and SOC declined with increasing soil depth for all tested sites. SSI and SOC were predominant factors contributing to the variation in soil erodibility, which were 34.9 % and 35.1 % at the upper spatial location, 31.4 % and 30.9 % at the middle spatial location, and 32.1 % and 32.6 % at the lower spatial location, respectively. There were significant variations in the K factor between the sloping cropland with rock outcrops and the control group. The variations in soil erodibility indicators with rock outcrops and spatial locations were attributed to the changes in soil particle distribution, soil bulk density and SOC. There was a significant linear correlation between the K factor and spatial location, slope gradient, coverage and height of rock outcrops. These results indicated that rock outcrops and their characteristics can reduce soil erosion intensity by redistributing precipitation and runoff, thus further affecting infiltration and soil erodibility. These findings are helpful to comprehend the processes and mechanisms of the spatial variation in soil erosion on sloping cropland with rock outcrops.

An innovative hydrological model for the sparsely-gauged Essequibo River basin, northern Amazonia

ABSTRACT Tropical river basins – crucial components of global water and carbon cycles – are threatened by logging, mining, agricultural conversion, and climate change. Thus, decision-makers require hydrological impact assessments to sustainably manage threatened basins, such as the ∼68,000 km2 Essequibo River basin in Guyana. Emerging global data products offer the potential to better understand sparsely-gauged basins. We combined new global meteorological and soils data with established in situ observations to build the first physically-based spatially-distributed hydrological model of the Essequibo. We developed new, open source, methods to translate global data (ERA5-Land, WFDE5, MSWEP, and IMERG) into a grid-based SHETRAN model. Comparing the performance of several global and local precipitation and evaporation datasets showed that WFDE5 precipitation, combined with ERA5-Land evaporation, yielded the best daily discharge simulations from 2000 to 2009, with close water balances (PBIAS = −3%) and good discharge peaks (NSE = 0.65). Finally, we tested model sensitivity to key parameters to show the importance of actual to potential evapotranspiration ratios, Strickler runoff coefficients, and subsurface saturated hydraulic conductivities. Our data translation methods can now be used to drive hydrological models nearly anywhere in the world, fostering the sustainable management of the Earth’s sparsely-gauged river basins.

Physical Properties of Retisol under Secondary Pulp and Paper Sludge Application

A positive effect of pulp and paper mill sludges as a rich source of organic substrates on soil properties was previously found for some types of sludge and soil. In this study, the effect of secondary pulp and paper sludge on water characteristics and thermal properties of Retisol, as well as the growth parameters of lettuce (Lactuca sativa L.), was tested on the basis of a pot experiment when watering plants with a 20 or 40% sludge solution. The sludge application enhanced plant growth with an increase in biomass accumulation of 21 and 53%, respectively, for 20 and 40% sludge treatments. When the sludge dose was increased from 0 to 40%, the number of leaves increased by 25%, and the leaf mass per area value increased by 42%. Due to the accumulation of more biomass in the shoots than in the roots, sludge causes a change in the allocation of plant biomass. A significant effect of the sludge application on soil particle and microaggregate sized compositions, as well as on the saturated soil hydraulic conductivity, was not found in this study. However, fitted soil water retention curves showed an increased soil water content in sludge-treated soil at all water content values exceeding field capacity. Secondary sludge application led to an increase in the saturated water content from 0.50 to 0.56 cm3 cm−3. The 40% sludge solution increased soil thermal conductivity from 0.92 to 0.98 W m−1 K−1 under saturated water content and from 0.83 to 0.92 W m−1 K−1 under field capacity. The thermal conductivity was higher in the sludge-treated than untreated soil due to a more pronounced positive effect of increased saturated water content than the negative effect of the increased organic matter content on heat transfer. The positive impact of secondary sludge application on both plant growth parameters and physical properties of Retisol, such as increased soil water-holding capacity and thermal conductivity coefficient confirms the possibility of using it to improve soil characteristics and plant productivity.

Spatiotemporal Heterogeneity of Water Conservation Function and Its Driving Factors in the Upper Yangtze River Basin

The water conservation function (WCF), as one of the most critical ecosystem services, has an important impact on the ecological sustainability of a region. Accurately characterizing the spatiotemporal heterogeneity of WCF and further exploring its driving factors are of great significance for river basin management. Here, the WCF of the upper Yangtze River basin (UYRB) from 1991 to 2020 was calculated using the water yield module in the Integrated Valuation of Ecosystem Service and Tradeoffs (InVEST) model. Also, we innovatively applied emerging hot spot analysis (EHSA), which could describe the location and pattern of historical changes more accurately, to investigate the spatiotemporal heterogeneity and evolution of WCF. Based on the Geographical Detector Model (GDM), the main driving factors of WCF and their interactions were revealed. The results showed the following: (1) the WCF in the UYRB experienced a temporal increase at a growth rate of 1.48 mm/a, while remarkable differences were observed across the change rates of sub-watersheds. (2) The spatial variation of the WCF showed a gradual increase from northwest to southeast. Interestingly, the Jinshajing River upstream (JSJU) source area with a low WCF showed an increasing trend (with diminishing cold spots). On the contrary, the downstream regions of the JSJU watershed (with intensifying cold spots) underwent a weakening WCF. (3) Among all driving factors, precipitation (q = 0.701) exhibited the most remarkable prominent impact on the spatial heterogeneity of the WCF. Additionally, the interaction of factors exhibited more explanatory power than each factor alone, such as precipitation and saturated soil hydraulic conductivity (q = 0.840). This research study is beneficial to water resource management and provides a theoretical basis for ecological restoration.

Approximation of van Genuchten Parameter Ranges from Hydraulic Conductivity Data.

The use of retention function and relative conductivity function is essential for the calculation of flow in a variably saturated media using the Richards equation. A widely used mathematical model for this is the Mualem-van Genuchten model which requires the shape parameters and . These, however, are difficult to obtain. When data is scarce, and are often taken from literature and may deviate largely from actual values. The current study presents a novel mathematical model for the approximation of and and for the further estimation of realistic value ranges, which may be used as parameter space, for example, for the calibration of a numerical model. The model was developed for cases where data is scarce and only values of saturated hydraulic conductivity are available. It is based on a large data set from literature and it is demonstrated that the model estimates mean values from that data set with a good accuracy. In order to show the applicability of the model, a second data set has been compiled anew (provided as Supporting Information). The model is incorporated into the current version of the freeware computer program HYPAGS, which enables easy usage.

Effect of Addition Nitrogen Fertilizer at Different Irrigation Levels on Saturated Hydraulic Conductivity by Using Two System of Irrigation

A field study was conducted in the province of Wasit - Kut, in a semi-arid region with a clay loam texture, for the purpose of studying the effect of adding nitrogen fertilizer, which included the level of 300 kg H-1 (N1) and 150 kg H-1 (N2) and the comparison treatment without adding fertilizer (N0) and using two levels of irrigation, which included EP (P1) 75%, EP (P2) 100% under drip irrigation (DI) and surface irrigation (SI) systems on saturated Hydraulic conductivity (Ks). The results showed that the addition of nitrogen fertilizer N1 had a significant effect by increasing the nitrogen availability using (DI), as the N1 gave the highest value of conductivity and a significant difference from the rest of the treatments, by increase 154.3% While the increase were 103.7% and 56.79% for the treatment N2 and N0, respectively. The results indicated that there were significant differences due to the effect of different irrigation levels on the Ks values, as P1 treatment gave the highest Ks value of 2.21 m day-1 compared with P2 treatment, which amounted to 1.94 m day-1, With the presence of significant differences for the two irrigation systems on the Ks values, as the values increased compared with the values before planting, with an increase of 129.6% and 38.27% for the (DI) and (SI) system. The study also showed that there were significant differences for the effect of the interaction between nitrogen fertilizer treatments and the irrigation levels, as well as the presence of significant differences for the effect of the interaction between the nitrogen fertilizer treatments and the irrigation system used on the Ks values.

Long‐term combined subsoiling and straw mulching conserves water and improves agricultural soil properties

AbstractSubsoiling and straw mulching are two techniques that conserve soil water and improve the sustainability of agricultural production. However, the benefits to soil sustainability of combining subsoiling with straw mulching under intensive rotation between wheat and maize remain uncertain. We conducted a field experiment to determine the long‐term impacts of conventional tillage with straw mulching (CS), and subsoiling with straw mulching (SS), on soil macropore characteristics (&gt;160 μm), soil aggregate characteristics, and soil hydraulic parameters at 0–100 cm depths. Results indicate that SS increased the mean macropore number (66.9%), macroporosity (93.5%), pore circularity (3.5%), field moisture capacity (11.8%), saturated moisture content (21.4%), available soil moisture content (24.1%), and the saturated hydraulic conductivity (39.3%) in the shallowest 50 cm of soil, and total organic carbon content (34.5%) and soil labile organic carbon (20.2%) in the shallowest 30 cm of soil, compared to CS. Compared with CS, SS was more effective at increasing the proportion of aggregates larger than 0.25 mm in the top 20 cm of soil and decreasing the proportion of aggregates smaller than 0.25 mm in the top 30 cm of soil. Correlations between soil organic carbon and various soil physical properties under different practices suggest that SS has larger causative effects on soil physical properties than CS. Therefore, SS is recommended over CS.