Initial Soil Research Articles

Influence of organo-chemical fertilizer mixed with hormones on yield of Zea mays (L.) and soil productivity

The effect of five fertilizers; NPK (15-15-15), organo-chemical hormone mixed formula 1 (HO-1), Formula 2 (HO-2), Formula 3 (HO-3) and granular organic fertilizer (GOF) were investigated on maize yield and soil properties in a Randomized Complete Block Design with 4 replications. The new hybrid maize (GT 822) was sown at 75 x 25 cm² spacing. The fertilizer rate was 300 kg ha-1. Initial soil analysis showed that the soil had a lower rate of nutrients but after the second season of trial a significant (p ≤ 0.05) improvement was observed in soil properties, the highest residual NPK of 0.875 %, 0.0275 %, and 0.0267 % were recorded in HO-3 plots. Vegetative data showed that maize height, dry matter, leaf area, and leaf chlorophyll of 270.85 cm, 282.66 g, 156.02 dm², and 56.70, respectively were also highest in HO-3 fertilizer. Plant growth indices; RGR, LAI, and dry matter use efficiency of 0.132 g g-1day-1, 5.90 and 34.4 %, respectively were best in HO-3. Grain yield and crude protein of 8276.68 kg ha-1 and 8.99 % were recorded in HO-3, followed by HO-2 and NPK. Lower yields were obtained from the control and GOF. Our finding revealed that the integration of nutrient sources in a balanced ratio produced the greatest yield output, improved soil properties, and is therefore the future approach to planning an effective fertilizer strategy. Reliance on GOF as a sole fertility package for maize production may result in significant yield losses compared to the integrated approach or use of NPK fertilizer.

Regulation of initial soil environmental factors on litter decomposition rate affects the estimation accuracy of litter mass loss in a subtropical forest

Regulation of initial soil environmental factors on litter decomposition rate affects the estimation accuracy of litter mass loss in a subtropical forest

Nanoporous zeolite and its effect on the immobilization of trace elements in soils from scrap landfills under aided phytostabilization

AbstractThe rising prerequisite for developing novel green remediation methods for trace‐element‐contaminated lands is allied to the necessity to really mend the soil environs. The effectiveness of zeolite‐aided phytostabilization (AP) of soil contaminated with trace elements (TEs), from a scrap yard, using Lolium perenne as the plant for testing, was determined and discussed. The variability and activity of the rhizospheric bacterial community were also examined. The initial soil used in the AP experiment was characterized by especially high total contents of Zn, Pb, Cu and Cd. The TE total contents in roots and aboveground parts of L. perenne as well as in the phytostabilized soil materials were analyzed with flame atomic absorption spectrometry. The study revealed that the addition of natural zeolite into TE‐contaminated soil increased the relative plant biomass as well as the soil pH value as compared to the phytostabilized non‐amended series, whereas the total contents (with respect to an absolute value) of Zn, Pb, Cu and Cd were generally higher in roots than in the aboveground parts of L. perenne. In particular, the incorporation of zeolite to the soil contributed most significantly to the considerable relative decrease in the total contents of Cu, Pb, Cd and Zn in the soil, as well as the content of bioavailable and leachable speciations of Cd, Cu, Zn and Pb extracted from the soil using CaCl2 solution as compared to the non‐amended series. In the phytostabilized zeolite‐amended soil, the overall bacterial diversity decreased but the presence of zeolite favoured the growth of microorganisms belonging to Gammaproteobacteria, Planctomycetia, and Thermomicrobia, in particular, the genera Mycobacterium, Williamsia, and Prochlorococcus.

Development of a soil wetting pattern estimation model for drip irrigation

Abstract Accurately estimating the soil wetting pattern that closely reflects the measured value can improve the water use efficiency for drip irrigation. Ignoring the effect of the initial soil water content on the soil wetting pattern affects the accuracy of the estimated results to a certain extent. This research aimed to develop a soil wetting pattern estimation model for drip irrigation that included four easily measurable parameters (i.e., initial soil water content, saturated hydraulic conductivity, total volume of applied water, and emitter discharge rate) based on dimensional analysis theory. In this study, the wetting front advance data of 12 typical soil textures were obtained in Hydrus-2D/3D. The estimated values were then compared with measured or simulated wetting front advance values. For different experiments, the mean absolute error, root mean square error, and mean relative error varied from 2.77 to 4.69 cm, 6.20 to 10.61 cm, and 5.61% to 10.51%, respectively. Compared with the existing models, the proposed model was more consistent between the measured and simulated values. Therefore, the proposed model of this study is efficient and simple, which can help accurately estimate the soil wetting pattern of drip irrigation with a variety of soil textures.

Effect of Soil Test Crop Response (STCR) and STCR –Integrated Plant Nutrition System (IPNS) Based Fertilizer Prescription Equations on Maize Productivity, Economics and Soil Fertility Status in Vertisols of Northern Karnataka

A study on Soil Test Crop Response based Integrated Plant Nutrition System (STCR - IPNS) was conducted adopting an Inductive cum Targeted yield model in vertisols of Northern Karnataka at Main Agricultural Research Station (MARS), UAS, Dharwad, Karnataka during kharif 2020-21 in order to develop STCR and STCR-IPNS fertilizer prescription equations (FPEs) for achieving desired yield targets of maize. Fertilizer doses at varying soil test values, for attaining 60, 80 and 100 q ha-1 target grain yield of maize have been worked out based on the initial soil test values of available N, P and K and the quantities of N, P and K added through farm yard manure (FYM). Using these equations, validation trials were conducted during kharif 2021-22 at MARS, Dharwad and Irrigation Water Management Research Centre (IWMRC), Belavatgi. The results of the experiment indicated that at both the locations, the per cent achievement of the targeted yield was within ± 10 % variation proving the validity of the equations for prescribing integrated fertilizer doses for maize. The highest grain yield was recorded in STCR-IPNS equation with 100 q ha-1 target yield (Dharwad -104.8 q ha-1, Belavatgi – 102.3 q ha-1) recording an increase of 67 and 69 per cent over recommended package of practices at Dharwad and Belavatgi, respectively. However, it was found to be on par with Jabalpur STCR equation with 100 q ha-1 target yield and STCR-NPK alone equation with 100 q ha-1 target yield. Higher gross returns were recorded under STCR-IPNS equation with 100 q ha-1 target yield owing to higher grain and stover yields. While STCR equation developed at Jabalpur with 100 q ha-1 target yield recorded higher net returns. The post-harvest soil available NPK indicated better build-up and maintenance of soil fertility by the soil test based fertilizer recommendation under IPNS. Targeting 100 q ha-1 grain yield for maize under STCR approach was found to be ideal in terms of yield, economics and soil fertility maintenance in vertisols of Karnataka. The fertilizer prescription equations developed for maize under IPNS can be recommended for vertisols of Northern Karnataka for achieving target yield of 100 q ha-1 with sustained soil fertility and it can be extrapolated to other agro-climatic zones of Karnataka on similar and allied soil types.

Managed aquifer recharge using a borrow pit in connection with the Mississippi River Valley alluvial aquifer in northeastern Arkansas

The Mississippi River Valley alluvial aquifer (MRVAA) is one of the overexploited aquifers in the United States. Agriculture in Arkansas relies significantly on the MRVAA for irrigation, due to its accessibility and high yield. Increased irrigation demand since the early 1900s with continued expansion and inequitable recharge contributions resulted in groundwater decline. Overdraft of the MRVAA in Arkansas has resulted in the designation of critical groundwater areas. Managed aquifer recharge (MAR) methods intentionally replenish stressed groundwater resources. A MAR case study was conducted to determine whether infiltration basins, as repurposed borrow pits, could be used to enhance groundwater decline in critical groundwater areas of northeast Arkansas. This rehabilitation would be a practical solution to alleviate groundwater decline as well as economically feasible as land would not need to be taken out of production. In 2015, the Arkansas Department of Transportation contracted sand excavation of fallow land owned by a collaborating producer. This borrow pit would serve as a test case to measure infiltration rates into the MRVAA using nearby surface water as the recharge source. Initial soil core analyses revealed soil properties within the confining clay layer of red-brown clay and silty clay soils (0 to 3.7 m deep) with sand below. Excavation completed to a depth of ~6 m exposed the uppermost-unsaturated section of the alluvial aquifer, consisting of well-sorted medium grain size sand. The borrow pit floor was ~27 m above the existing water table, and it was hypothesized that this exposed unsaturated aquifer section would provide a natural filter and an avenue for increased water storage underground. Sediment samples were collected from the pit floor and sidewall pre- and postexperiment to characterize particle size, textural class, and organic matter. Submersible pressure transducers were installed within the pit and in a nearby irrigation well to monitor water level changes. Meteorological data were collected on-site to measure the water budget components of precipitation and evaporation. Water level declines and infiltration were evident throughout the experiment. An initial infiltration rate of 192 mm d⁻¹ was measured in February of 2016 that decreased until March, with steady state rates of 4.43 to 136 mm d⁻¹ that varied until June. An overall integrated infiltration rate of 36.4 mm d⁻¹ was calculated from the water budget. Total subsurface storage increased by 9.3 ML from February to June of 2016, and a two-dimensional simulation predicted a maximum groundwater mounding of 2.6 m during the experiment. Additionally, 14 borrow pits that had not been repurposed were identified in the area using remote sensing. Results of this study demonstrate that a relatively inexpensive MAR strategy could be implemented using former borrow pits repurposed as infiltration basins to alleviate groundwater decline in a critical groundwater area of northeastern Arkansas.

Deciphering nitrous oxide emissions from tropical soils of different land uses

Tropical regions are hotspots of increasing greenhouse gas emissions associated with land-use change. Although many field studies have quantified soil fluxes of nitrous oxide (N2O; a potent greenhouse gas) from various land uses, the driving mechanisms remain uncertain. Here, we used tropical soils of diverse land uses and actively manipulated the soil moisture (35%, 60%, and 95% water-filled pore space [WFPS]) and substrate supply (control, nitrate, and nitrate plus glucose) to investigate the responses of N2O emissions with short-term incubations. We then identified key factors regulating N2O emissions out of a series of soil physicochemical and biological factors and explored how these factors interacted to drive N2O emissions. Land-use changes from primary forest to oil palm or Acacia plantation risks emitting more N2O, whereas low emissions could be maintained by conversion to Macaranga forest or Imperata grassland; these laboratory observations were corroborated by a literature synthesis of field N2O measurements across tropical regions. Soil redox potential (Eh) and labile organic nitrogen (LON; amino acid mixture, arginine, and urea) mineralization were among the factors with greatest influence on N2O emissions. In contrast to common understandings, the control of WFPS over N2O emissions was largely indirect, and acted through Eh. The mineralization of LON, particularly arginine, potentially played multiple roles in N2O production (e.g., bottlenecks of nitrifier-denitrification or simultaneous nitrification-denitrification versus substrate competition for co-denitrification). Structural equation models suggest that soil-environmental factors of different levels (from distal including land use, soil moisture, and pH to proximal such as LON mineralization) drive N2O emissions through cascading interactions. Overall, we show that, despite identical initial soil conditions, land conversion can substantially alter the N2O emission potential. Also, collectively considering soil-environmental regulators and their interactions associated with land conversion is crucial to predict and design mitigation strategies for N2O emissions from land-use change.

Effects of Alternate Wetting and Drying Water Levels and Planting Methods on Performance of Rice (Oryza Sativa L.) and Selected Soil Properties in a Nigerian Sudan Savanna

This study was conducted to determine the effect of changing the depths of water and planting methods on soil properties and rice yields under alternate wetting and drying (AWD) in the Systems of Rice Intensification (SRI). The treatments consisted of four irrigation levels and four planting methods. The irrigation treatments included 4 water drop levels (WDL) in observation well: 6 cm, 10 cm, 14 cm water drop levels below the soil surface and continuous flooding with 5 cm layer of water above soil. Four planting methods included seed drilling, broadcasting, transplanting 12 day old seedling and transplanting 21 day-old seedlings. Lowland rice (FARO 44) was established in randomized complete block design. Alternate wetting and drying at 6 and 14 cm WDL showed 14.27 % and 11.59 % increase in total porosity respectively, when compared with initial soil total porosity. All plots showed a decrease in bulk density compared with initial soil bulk density. Paddy yield for irrigation treatments ranged between 6.03-9.92 t ha-1, with AWD at 10 cm WDL having highest yield of 9.92 t ha-1, the lowest was observed in the continuously flooded plots (6.03t ha-1). System of rice intensification method of transplanting was observed to yield 10.08 t ha-1 of paddy and showed percentage increases in paddy yields by 26.3%, 69.9% and 33.5% over conventional transplanting (21 day seedling), broadcasting and drilling, respectively. This study showed the superiority of using younger seedlings in transplanting and 10cm water drop level in the observation well for increased food security and income.

Smart Farming for Smart Future of Agriculture

The domestication of animals and plant cultivation through the adoption of systematic farming practices, as well as the green revolution brought on by the invention of chemical fertilizers and the introduction of hybrid varieties a few decades ago, are just a few of the revolutions that have occurred in agriculture. Now it is the phase of agriculture revolution 4.0 triggered by the exponentially increased use of ICT in agriculture. The smart farming with the help of ICT technologies could bring out possible solution to the challenges faced in agriculture sector that includes lack of resources, climate change etc. The objective of the present investigation was to compare the yield and nutrient requirement (NPK) for cultivating sweet potato (Ipomoea batatas) under smart farming and farmer’s practice as a field trial in a farmer’s plot at Nedumangad block of Thiruvananthapuram district. Under smart farming practice, the agro advisory for cultivating the crop was given through SMS to the farmers in every ten days’ interval. The advisory was generated based on the field’s real-time weather parameters, crop stage, and initial soil analysis. Results revealed that smart farming plots recorded higher yields with lower nutrient application. This technology can be replicated in any crop including rice.

Modeling management of continuous dryland cotton with an intervening winter wheat cover crop in a semiarid climate

Although winter cover crop residue can mitigate the stresses of dryland production in semi-arid regions, cover crops can also reduce soil moisture and cash crop yields. In some field studies of dryland cotton grown after terminated winter wheat in the U.S. Southern High Plains (SHP) and Texas Rolling Plains cotton yields were increased relative to continuous cotton, while others had no significant yield or soil water effect. These uncertain outcomes may be due to the trial's limited sampling of seasonal rainfall conditions. To estimate the probabilities of cover crop effects under more representative SHP climate conditions, 294 station-years of crop model simulations of terminated winter wheat followed by dryland cotton were conducted. These simulations were driven by weather data from 21 SHP weather stations during 2005–2019. Each station-year's simulations were repeated under 54 combinations of wheat planting, termination, and cotton planting dates, 2 soil series with different water capacities, and 10 initial soil moisture conditions. When simulations begin with fall soil moisture at field capacity optimal management options for both soils plant wheat early and cotton late, but have different wheat termination dates. Before cotton planting winter cover crop effects are dominated by reduced surface evaporation and increased transpiration, with greater transpiration effects producing decreased column soil moisture (CSM) at wheat termination. Some soil moisture recharge occurs between termination and cotton planting, but cover crops reduce CSM at cotton planting in both soils in ~75% of simulations. Reduced soil evaporation and soil moisture recovery continues after cotton planting, resulting in positive effects on seed cotton yield in 50% of the silty clay loam simulations and in 67% of the fine sandy loam simulations. Gradually reducing initial fall soil moisture in the silty clay loam reduces wheat biomass but increases the incidence of positive effects on seed cotton yields and CSM at cotton planting and harvest. By contrast, drier initial soil moisture in the fine sandy loam had relatively minor yield and CSM effects. In both soils terminated wheat residue led to increased CSM at cotton harvest in at least 70% of the simulations regardless of soil moisture at wheat planting.

Influence of soil density on the solid-to-fluid phase transition in flowslide flume experiments

Flowslides are extremely hazardous due to their sudden failure and rapid flow-like motion. Focusing on the transient solid-to-fluid phase transition, we carried out a series of flume studies following various experimental scenarios, simultaneously recording granular velocity distributions, pore-water pressures, microseismicity, and acoustic emissions with precise time resolution (±0.01 s). The solid-to-fluid phase transition was recognized from the transition from solid-like shear deformation to flow-like velocity distribution. The variation in excess pore pressure in slopes during failure differed depending on initial soil state parameters, resulting in different failure patterns and distinct solid-to-fluid phase transition dynamics: (i) diffuse failure in loose slopes, the soil instability caused by increased local pore pressure (far from liquefaction) can trigger the whole failure of the slope; (ii) Mohr-coulomb failures in denser slopes, the soil mass slid along a localized shear zone, and progressively evolved to a diffuse shear throughout the slide mass. and (iii) retrogressive failures in very dense slopes. During the rapid motion process, the soil mass behaved as a fluid even after the excess pore pressure had dissipated, demonstrating that mechanisms other than soil liquefaction governed the fluid-like behavior. We inferred that the fluidization originated from the inherent shear-rate-dependent behavior of granular materials. Additional evidence for this hypothesis was provided by ultra-high frequency acoustic emissions (approximately 100 kHz) suggesting grain-scale collisions accompanying the fluidized runout.

Multi-objective optimization of winter irrigation for cotton fields in salinized freeze-thaw areas

The adaptive management of saline-alkali land and water resources can effectively alleviate land degradation and water depletion, and appropriate irrigation can improve crop yield and production efficiency. Based on the soil changes and comprehensive crop benefits under different initial soil environments, the optimization of the irrigation amount of cotton in saline-alkali areas is of great significance for the improvement of agricultural production of these areas in developing countries and even worldwide. The responses of farmland with various degree of salinization to different winter irrigation amounts in seasonal freeze-thaw arid areas should therefore be further explored. In this study, the soil moisture-temperature-salinity changes and the crop growth responses of three cotton fields with different salinization levels (5.15, 8.17, and 11.15 g·kg-1) under four winter irrigation amounts (0, 3000, 3600, and 4200 m3·ha-1) were intensively investigated via a two-year field experiment in Xinjiang Province, China. The results demonstrate that winter irrigation significantly improved the soil moisture-temperature-salinity environment during the freeze-thaw period, and the influence was affected by the field salinization level. The initial salinity of salinized field promoted soil thawing and water storage, and inhibited soil freezing and salt leaching. The intraspecific relationship of salinized cotton fields changed from competition to promotion under winter irrigation, and soil salinity weakened the optimization of the intraspecific relationship. The multiple correlations between the benefit indexes of cotton were significantly strengthened under winter irrigation, and the negative effect of the soil salinization level on the cotton benefit indexes was stronger than that of the winter irrigation amount. Based on a multiple regression analysis, the optimal winter irrigation amounts for cotton fields with mild, moderate, and severe salinization were found to be 3416.83–4256.14, 4256.14–6502.96, and 6502.96–9614.24 m3·ha-1, respectively. This research provides a theoretical basis for determining the appropriate winter irrigation amount for cotton fields with various degrees of salinization in seasonal freeze-thaw arid regions.

Shear Strength Behaviour of Sedimentary Soil Stabilized by Fly Ash

Sedimentary soil is made up of deposits that are the consequence of the weathering of rocks that have already been deposited elsewhere by various natural processes, including water, wind, and others. A location with sedimentary soil is the Bili-bili Dam in the South Sulawesi Province's Gowa Regency. Sedimentary soil at this location is quite abundant and has not been used in general, so it can be investigated for its use, namely stability against the influence of external forces on the carrying capacity of the sedimentary soil. Stabilizing the soil is one approach to boost its bearing capacity, particularly for sedimentary soil. The original soil is categorized as group A-4, or silty soil, according to the AASHTO classification system and as ML, or silt with low plasticity, according to the USCS classification system, based on the findings of physical characteristics testing. It has been demonstrated that the soil's cohesiveness and shear angle increase with the addition of fly ash. It has been demonstrated that adding fly ash stabilizing material to the sedimentary soil of the Bili-bili Dam and allowing it to cure increased the cohesion value from the initial soil cohesion value of 0.72 kg/cm2 to 1.70 kg/cm2 after 28 days. With a 20% fly ash mixture and a curing period of 28 days, the shear angle value increased from the initial soil shear angle value of 22 to 31; this is a 40% increase in the shear angle value.

Effect of Different Amendments and Inorganic Nutrient Management Approaches in Correcting Sodicity under Paddy Eco System

Agricultural production in sodic soil may be hindered by its unfavorable physicochemical properties. In order to find effective measure to improve the health of sodic soil and make it to favourable for crop production, a field experiment was conducted at ZARS VC Farm Mandya to study the effect of different amendments on properties of sodic soil. The experiment was laid under split plot design with inorganic nutrient management viz., RDF, SSNM and STCR as main treatments and amendments such as press mud, gypsum and Mangala setright, (a commercial soil conditioner containing 15% calcium and 3% magnesium and 5% sulphur) as sub treatments. Results of experiment revealed that application of gypsum significantly reduced pH to 8.5 from 8.96 of initial soil which was on par with application of setright at 600kg/ha (8.68) and press mud (8.69). Whereas exchangeable sodium and ESP was reduced significantly due to application of setright at 400 kg/ha (1.78 cmol/kg and 6.52 respectively) and pressmud at 100% GR (1.85 cmol/kg and 7.03) compared to control (3.69 cmol/kg and 13.72 respectively) and initial soil. Thus application of Mangala Setright at 400kg/ha or pressmud at 100% GR are more beneficial in rectifying sodicity of soil.

How does uncertainty of soil organic carbon stock affect the calculation of carbon budgets and soil carbon credits for croplands in the U.S. Midwest?

Cropland carbon budget depicts the amount of carbon flowing in and out of agroecosystems and the changes in carbon stocks of soil and living biomass during the same period. Soil carbon credit is the additional change in soil carbon stock under certain farming practices compared with the business-as-usual practices. Accurately calculating cropland carbon budget and soil carbon credit is critical to assessing climate change mitigation potential in agroecosystems. The calculation of cropland carbon budget and soil carbon credit is sensitive to local soil and climatic conditions, especially initial soil organic carbon (SOC) stock, which is determined by both SOC concentration (SOC%) and bulk density (Bulk_Density). SOC stock data are either from soil sampling or gridded public survey data. In agroecosystem models, SOC stock data are a key model input for quantifying cropland carbon budget and soil carbon credit. However, various types and degrees of uncertainties exist in SOC stock datasets, which propagate to the quantification of SOC stock change. In particular, a large discrepancy is found in two widely used SOC stock datasets — Rapid Carbon Assessment dataset (RaCA) and Gridded Soil Survey Geographic Database (gSSURGO) — in the U.S. Midwest, with a relative difference (quantified using Normalized Root Mean Square Error, NRMSE) of 48.0% for 0–30 cm SOC stock between the two datasets. It remains largely unclear how uncertainty in SOC stocks affects the calculation of cropland carbon budget and soil carbon credit. To address this question, we used a well-validated process-based agroecosystem model, ecosys, to assess the impacts of SOC stock uncertainty on carbon budget and soil carbon credit calculation in the U.S. Midwestern corn-soybean rotation systems. Our results reveal the following findings: (1) A sizable discrepancy exists in simulated cropland carbon budget between using gSSURGO and using RaCA for their SOC% and Bulk_Density as model inputs, with a Pearson correlation coefficient (r) of only 0.4 for simulated change of SOC stock (ΔSOC) using these two different soil datasets. (2) Simulated cropland carbon budget components were more sensitive to initial SOC% than to Bulk_Density. For example, the upper and lower quartiles of multi-year averaged ΔSOC were −29.8 and 4.8 gC/m2/year for the selected counties respectively, with an uncertainty of 13.7 and 0.7 gC/m2/year induced by uncertainties in initial SOC% and Bulk_Density, respectively. (3) Both simulated ΔSOC and its uncertainty were negatively correlated with initial SOC%, whereas ΔSOC was negatively correlated with air temperature, and ΔSOC uncertainty was positively correlated with air temperature. (4) The uncertainty of calculated soil carbon credits was much smaller compared with the uncertainty of calculated absolute carbon budgets assuming the same SOC stock uncertainty level in the inputs. Specifically, in our assessment comparing planting cover crops vs no cover crop, the uncertainty of calculated soil carbon credits induced by initial SOC% uncertainty was less than 4% (relative to the quantified value of the soil carbon credits) for 90% of the cases. Our analysis highlights that high accuracy measurement of SOC% as inputs is needed for the calculation of cropland carbon budgets; however, soil carbon credit quantification is much less sensitive to the initial SOC% inputs, and the current publicly available soil datasets (e.g., gSSURGO) are largely suitable for the calculation of soil carbon credits.

Dynamic Heat Transfer Calculation for Ground-Coupled Floor in Emergency Temporary Housing

Generally, ground-coupled floor heat transfer is supposed as annual periodic, which is reasonable for conventional buildings. However, for emergency housing with a short life cycle, the influence of initial soil temperature needs to be considered. In a previous study, the Wiener–Hopf technique was introduced to solve the two-dimensional transient heat transfer equation with mixed Dirichlet and Robin boundary conditions. Based on that, an analytical solution of the dynamic heat transfer equation with initial soil temperature conditions was obtained. Since the solution was in the form of a double integral, its numerical evaluation method was also analyzed to improve computational efficiency. The accuracy and efficiency of the solution were validated by the finite volume method. Then, the effects of initial soil temperatures in different seasons, soil heat conductivities, and floor insulation on ground-coupled heat transfer were discussed. Results showed significant temperature differences between the current solution and the annual periodic solutions (long-time solutions), especially in hot and cold climates. Moreover, the larger the thermal capacity of the soil, the bigger temperature differences occurred. Therefore, this study is expected to provide a theoretical foundation for the indoor environment prediction and optimization design of emergency temporary housing.

Green infrastructure drainage of a commercial plaza without directly connected impervious areas: a case study.

A paired-catchment study of two adjacent commercial areas in northern Sweden, one with Green Infrastructure (GI) storm drainage and the other with a conventional storm sewer system, served to evaluate the hydrological performance of both drainage systems and demonstrate advantages of GI. The GI catchment avoided directly connected impervious areas by diverting runoff from a parking lot to a cascade of three infiltration features, a fractured rock strip draining onto a sloping infiltration area, followed by a collector swale. Both catchments were monitored over 4 years by measuring rainfall, runoff and, in the vicinity of the swale, soil water content and groundwater levels. For frequent storms, the median GI efficiencies in reducing runoff volumes and peak flows, and extending peak flow lags, were 96, 99 and 60%, respectively, compared to conventional drainage. The storm rainfall depth, initial soil water content, increases in intra-event soil water storage and groundwater levels had statistically significant effects on either runoff volume or peak flow reductions. No effects were found for storm rainfall intensity and duration, antecedent dry days, and initial groundwater levels. The study demonstrated that GI drainage can be successfully applied even in the challenging environment of a subarctic climate.

Evaporation effect of infiltration hole and its comparison with mulching

Reducing ineffective evaporation of soil water is an important way to relieve drought in semi-arid rainfed agricultural areas. An infiltration hole is a supplemental measure for slope rainwater harvesting measure and is commonly used in vegetation restoration and orchard management of slopes. However, the evaporation effects of infiltration holes are unclear. In this study, we determined the evaporation effects of infiltration holes under a high initial soil water content and compared the differences in inhibition of soil evaporation among infiltration holes, mulching, and their combination after a rainstorm event. The results showed that the infiltration holes at different depths increased soil daily evaporation in the first 26 days under the high initial soil water content, after which it decreased. Compared with the control, the average daily evaporation while covering the top surface and the hole (sidewall and bottom) decreased by 74.3% and 4.3%, respectively. After the rainstorm event, cumulative evaporation (97 days) significantly decreased by 42.0% and 34.0% under the infiltration hole compared to gravel mulching and branch mulching, respectively. Overall, the infiltration hole increased soil evaporation at the early stage. Soil water mainly evaporated through the top surface of the soil column rather than through the hole itself. In the long term after rainstorms, infiltration holes have better effects in inhibiting evaporation than mulching. Our findings determine the evaporation effects of infiltration holes in the process of harvesting rainwater to replenish soil water in semi-arid rainfed agricultural areas.

An improved estimation of soil water and salt dynamics by considering soil bulk density changes under freeze/thaw conditions in arid areas with shallow groundwater tables

Soil bulk density (BD) is a parameter dependent on soil texture, compositions of soil minerals and organic matter and the extent of soil compaction. Seasonal freeze/thaw in arid areas with shallow groundwater tables (AASGT) may significantly change BD and hence soil hydrothermal properties and water holding capacity. Therefore, quantifying soil bulk density changes (BDC) under freeze/thaw conditions can improve estimates of soil water-salt dynamics in AASGT. In this study, we conducted field experiments to investigate the soil water-salt dynamics under freeze/thaw conditions from three typical land-use types (i.e., farmland, woodland, and natural land) in the upper Yellow River basin, China. We proposed a method to estimate BDC, which can better describe the soil water-salt dynamics during the freeze/thaw period. Our results showed marked BDC occurred in all layers within the 0–100 cm profile in natural land, while mainly at the 20–80 cm profile in farmland. During the freezing period, BD in farmland and natural land first decreased rapidly and then remained relatively stable until the thawing period started. After that, BD gradually increased during the thawing period. The largest BDC in farmland and natural land were 0.48 g cm−3 (occurring at the 30–40 cm layer) and 0.43 g cm−3 (occurring at the 80–90 cm layer), respectively, close to 30 % of their initial values. The differences in BDC between the three land-use types were mainly owing to their differences in groundwater table depth, initial soil salt concentration, soil texture, and surface coverage conditions. Moreover, in farmland and natural land, ignoring BDC resulted in different degrees of overestimation or underestimation in soil water content, water fluxes, and soil hydrothermal properties in the selected soil layers. This study demonstrates that considering BDC can improve the accuracy of soil water-salt dynamics estimation in AASGT under freeze/thaw conditions.

Generalized strength prediction equation for cement stabilized clayey soils

The role of clay minerals on the strength development of cement stabilized clays at different cement contents, water contents and curing times was studied in this research. Kaolin and sodium bentonite were used to represent non-swelling and high swelling soils respectively. The soils studied were mixtures of kaolin and bentonite at replacement ratios of 0, 25, 50, 75, and 100% of the dry weight of bentonite to have various swelling potentials. The water content of the soil samples was adjusted to the optimum water content (OWC) and to the liquidity index (LI) of 0.25–1.50, so as to simulate different initial soil phases. The macro- and micro-observation indicated that the clay mineral, water content and cement content were the predominant influence factors controlling the strength development of cement stabilized clays, at a particular curing time. For a particular clay mineral, the total soil water to cement content, s-w/c was found to be the prime parameter reflecting the effect from both water content and cement content on the strength development in cement stabilized clay. The generalized strength model can be represented in the form: qu = A/B(s-w/c) where qu is unconfined compression strength, and A and B are constant. The values of parameters A and B were found to be primarily controlled by the clay mineral, which was found to be described by plasticity index. The generalized strength model was validated using separated test data. This model will facilitate the engineering decision of selecting the water content and cement content to attain the target strengths of clayey soils at required curing time with minimum number of trials.