Bulk Soil Electrical Conductivity Research Articles

Influences of grassland to cropland conversion on select soil properties, microbiome and agricultural emissions

Context Conversion of grasslands to croplands can usually result in the degradation of soils and increased greenhouse gas (GHG) emissions such as carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). However, little is known about the impacts of grassland conversion to recently tilled croplands on soils and GHG fluxes. Aims A field experiment was established in 2016 to evaluate the impacts of grassland conversion to tilled cropland under different landscape positions (upslope, backslope, and footslope) on select soil properties and soil GHG fluxes. Key results The findings showed that the grassland conversion significantly increased soil bulk density and electrical conductivity but reduced pH and total nitrogen (TN). The conversion impacted soil biome community grassland and tilled croplands. The landscape position significantly impacted soil pH (footslope < upslope) and TN (footslope > upslope). The grassland conversion significantly decreased soil CO2 fluxes, but increased soil CH4 and N2O fluxes. The landscape position significantly impacted soil CO2 (footslope > upslope and backslope) and CH4 (upslope > footslope and backslope) fluxes for some periods. Soil CO2 and N2O fluxes generally followed upward and downward trends over time, respectively. Conclusions These results indicate that grassland conversion was able to lose soil N, increase soil compaction, acidity, salts, and soil N2O and CH4 fluxes, and decrease the diversity of abundant genera and CO2 fluxes. Footslope increased TN, soil acidity, CO2, and CH4 fluxes, compared with upslope and backslope. CO2 fluxes under grassland and tilled cropland significantly increased over time, whereas N2O fluxes under grassland significantly reduced. Implications Conversion of grassland to tilled cropland significantly impacted on sol quality. It caused a loss in soil N and increased soil compaction, acidity and salts. Grassland conversion also decreased the abundance and diversity soil microbiome.

Rhizosphere soil properties, microbial community, and enzyme activities: Short-term responses to partial substitution of chemical fertilizer with organic manure

The partial substitution of chemical fertilizers with organic manure has positive effects on crop productivity and sustainable development. Nevertheless, few studies have focused on major grain crops. Herein, we report the short-term effects of the partial substitution of chemical fertilizers with organic manure on the physicochemical properties, microbial community, and enzyme activities in the rhizosphere soil of a maize (Zea mays L.) field. A decrease in soil bulk density, pH, and electrical conductivity, concomitant with an increase in soil urease, invertase, and alkaline phosphatase activities, and a high level of nutrients were observed in organic manure-treated soil. The influence of the organic substitution treatment on bacterial diversity was greater than that on fungal diversity, particularly on alpha diversity. Among dominant bacterial phyla, Actinobacteria abundance changed the most, with significantly increase under organic manure treatment. In turn, among fungi, only Ascomycota responded substantially to organic substitution. Binding spatial ordination analysis revealed that relative soil water content and soil organic carbon, and nitrate and total nitrogen contents had a stronger effect on bacteria and fungi, respectively, than any other soil physicochemical property. Additionally, the changes in bacterial and fungal communities influenced soil enzymatic activities. Moreover, partial least squares path model revealed that soil physicochemical properties indirectly affected soil enzymatic activities by their direct effects on microbial (both bacteria and fungi) community. Overall, our results indicate that the substitution of chemical fertilizers by organic manure changed the composition of the soil microbial community, and that the effects of the substitution were more significant on bacteria than on fungi.

Synergetic variations of active layer soil water and salt in a permafrost-affected meadow in the headwater area of the Yellow River, northeastern Qinghai–Tibet plateau

The coupling effects and mechanisms of water, heat, and salt in frozen soils are considered to be one of the core scientific issues in frozen soil studies. This study was based on in situ observation data of active layer soil volumetric water content (VWC), temperature, and bulk electrical conductivity (EC) obtained at an alpine meadow site from October 2016 to November 2019. The site is located in the headwater area of the Yellow River (HAYR). We analyzed the synergetic variations of active layer soil VWC, temperature, and bulk EC during the freeze and thaw processes and discussed the underlying mechanisms. When the thaw process occurred from 10 to 80 cm depths, the VWC and bulk EC at a 10 cm depth showed synchronous high-frequency fluctuations and both increased linearly. The linear decreasing rate of the VWC (bulk EC) at an 80 cm depth in the freeze depths between 0 and 40 cm was 2 (1.6–2.3) times that of the VWC (bulk EC) at an 80 cm depth in the freeze depths occurring 0–10 cm. As soil temperature decreased in the frozen layer, unfrozen water content (bulk EC) decreased nonlinearly along with the absolute value of soil temperature (|T|), following a power (logarithmic) function. This study provided data that partly elucidate the interactions among permafrost, meadow, and ecohydrological processes in the HAYR. Also, our results can be used as a scientific basis for decision making on the protection and restoration of alpine grasslands, as well as for soil salinization studies.

Investigation of Soil Physicochemical Effects on the Corrosion of Buried Iron Pipes

Soil corrosivity was an active problem of water pipeline damaged by corrosion that affects the performance of pipe manufacturers. In Addis ababa, groundwater pipelines were facing breakage and like due to corrosion damage of the pipes. The population of nearly four million were facing a shortage of clean and continuous water supply. Maintenace and replacing old pipes with new ones increased additional cost and delay of water supply for the city. For this investigation of corrosion, causes were conducted which soil property is the one factor. Investigation of soil corrosivity for a given specific location before installation is important to design robust pipes that can serve for long life. Soil physicochemical behaviors of the soil parameters were pH, moisture content, and electrical resistivity for any type of soil. In addition, soil bulk density, total nitrogen, soil texture, and electrical conductivity were also the main factors to be studied. The laboratory result indicated that pH of 6.98-7.04, moisture content of 23.7-37.5%, and electrical conductivity of 0.105-313 ds/m were observed. Total nitrogen was small as 0.06-0.10 for a type of soil were class and loam soils. From the analysis of eight soil samples taken from different cities. The results show that the corrosivity behavior of buried iron pipes in the capital city of Ethiopia was moderately corrosive. As confirmed from various soil samples tested from corroded pipes at different depths of 40, 80, and 120 cm. The influence of soil corrosiveness factors initiates pits formation and propagates its width and depth on the surface of pipes.

Time‐lapse imaging of soil moisture using electromagnetic conductivity imaging: Wetting phase

AbstractThe Vertosols of the lower Namoi valley in New South Wales, Australia, have been extensively developed for irrigated cotton (Gossypium hirsutum L.) production. However, there are competing demands for water from mining, environmental needs, and agriculture, with climate change forecasts suggesting reduced rainfall and hotter climates. This means irrigators need to improve water efficiency, which requires methods to monitor the soil volumetric water content (θ, m3 m–3). The aim of this study is to assess if a multicoil electromagnetic instrument (DUALEM‐421), which measures soil apparent electrical conductivity (ECa, mS m–1), can be used to value add to limited measurements of θ and allow extrapolation along a uniformly heavy clay irrigation furrow. Specifically, we seek to invert ECa using EM4Soil software to generate electromagnetic conductivity images, whereby the estimates of soil true electrical conductivity (σ, mS m–1) in the topsoil, subsurface, and subsoil are correlated with θ measured by Decagon GS3 sensors installed at the same depths. We also compared the usefulness of inversion of different combinations of DUALEM ECa: DUALEM‐1, DUALEM‐2, and DUALEM‐21. We found estimated σ from inversion of DUALEM‐421 ECa had good agreement (i.e., Lin's concordance = .84) with measured soil bulk electrical conductivity (σb, mS m–1). We explored the relationship between DUALEM‐421 estimated σ and θ using an artificial neural network. The predictions showed the model had good coefficient of determination (R2 = .74) with good accuracy (RMSE = 0.04 m3 m–3) and demonstrated good agreement between measured and predicted θ (Lin's = .84).

Detection of ionic contaminants in unsaturated soils using time domain reflectometry penetrometer

Previous investigations using time domain reflectometry (TDR) to detect ionic contaminants has mainly focused on saturated coarse-grained soils and conventional probes (e.g., coaxial, two- or three-rod probe). To explore the applicability of using the TDR penetrometer for the site investigation of ionically contaminated land, a theoretical framework was proposed to estimate the pore water electrical conductivity of both saturated and unsaturated silts based on measured soil dielectric permittivity and bulk electrical conductivity. The theoretical framework consists of three equations, the empirical equation relating soil dielectric permittivity and volumetric water content, the soil dielectric mixing model, and the modified Archie’s law considering the surface conductivity. To verify the theoretical framework, chamber tests using the TDR penetrometer were performed to detect CuSO4 contaminants in silt columns. Results show that the theoretical framework provides an increasingly better calculation of the pore water electrical conductivity of saturated and unsaturated silt with increasing the concentration of CuSO4 solution. This is because that the modified Archie’s law with a constant surface conductivity in the theoretical framework can well capture the relationship between soil bulk electrical conductivity and pore water electrical conductivity at high solution concentrations (i.e., 0.015 and 0.030 mol/L CuSO4 solutions), but not at low solution concentrations (i.e., tap water). The theoretical framework and chamber tests are expected to provide scientific guidance for extending the capacity of TDR penetrometer to the site investigation of ionically contaminated land.

A general form of Archie’s model for estimating bulk soil electrical conductivity

Electrical conductivity can be used as a surrogate to study the spatial and temporal variabilities of a number of soil properties, e.g., porosity, salinity, clay content and soil moisture. In this study, we develop a general form of Archie’s model that describes the relationship between soil electrical conductivity (σ) and volumetric water content (θ). The input parameters include θ, σ values at dry and saturated conditions (σdry and σsat), soil porosity (ϕ) and sand, silt and clay contents. A value of 2 was given to the water phase exponent (w) based on model calibration with σ and θ datasets obtained from 15 soils. The general form of Archie’s model was evaluated by comparing soil σ estimates to measured σ values from an additional 6 soils. The new model performed well by providing estimates with root mean square errors in the range of 0.008–0.399 dS m−1 and relative errors ranging from 0.7% to 29.8%. The new model is simple, easy to use and ready for further evaluation on a wide range of soil conditions.

Estimation of soil water retention curves from soil bulk electrical conductivity and water content measurements

Measurement of soil water retention curves (SWRCs) is time consuming, and there is no single laboratory device available to measure a SWRC over an entire range of relevant pressures. The van Genuchten (vG) model is commonly used to characterize the shape of the SWRC. Bulk soil electrical conductivity as a function of water content, σ(θ), has been used to estimate hydraulic properties of unsaturated soils, thus making it possible to relate σ(θ) and SWRC. The saturated and residual water content values, θs and θr, can be estimated from soil bulk density and particle size distribution. In this study, we present an approach to estimate vG parameters m and α from σ measured at saturated and residual soil water contents, as well as σ(θ) values measured at intermediate water contents. A thermo-time domain reflectometry (thermo-TDR) sensor is used to measure σ and θ of the same soil sample volume. SWRCs for three soils (Glassil 530 sand, Tennessee silt loam and Illinois clay loam with bulk densities ranging from 1.52 to 1.67 g cm−3, 1.05 to 1.25 g cm−3 and 1.05 to 1.2 g cm−3, respectively) are estimated from σ(θ) measurements and compared with direct SWRC measurements obtained with a tension table and pressure plate extractors. Additional comparisons are made using data obtained from the literature. The proposed method to estimate SWRCs performs well when compared to direct SWRC measurements (with an average RMSE and an average bias of 0.041 cm3 cm−3 and 0.008 cm3 cm−3, respectively). Results indicate that the new σ(θ) based method accurately estimates SWRCs.

Response of Soil Properties and Microbial Communities to Increasing Salinization in the Meadow Grassland of Northeast China.

Secondary salinization is a serious environmental issue and a major threat to the sustainable use of grasslands. Information about the response of microbial communities and soil properties in already saline soils to increasing salinity is lacking. We investigated soil properties and the structures of soil bacterial and fungal communities across a gradient of salinization in the Horqin Grassland, China. Three sites with relatively lightly (average soluble salt content = 0.11%), relatively moderately (average soluble salt content = 0.44%), and heavily (average soluble salt content = 1.07%) degraded grassland, were selected as experimental sites. We examined variations in the composition and structure of the soil bacterial and fungal communities by using high-throughput sequencing of the 16S and 18S rRNA genes, respectively. We found degrading effects of salinization on soil properties, i.e., decreased soil moisture, organic matter, total N, NH4-N, and NO3-N and increased soil bulk density, pH, and electrical conductivity. The bacterial and fungal community structures changed with increasing salinity. However, dominant microbial taxa (including phylum, genus, and operational taxonomic unit levels) were similar among experimental sites, indicating that increasing salinization slightly affected the basic compositions of microbial communities in already saline grasslands. Furthermore, the relative abundances of most dominant taxa sensitively responded to the soil salt content. Acidobacteria, Actinobacteria, Chloroflexi, RB4, Rubrobacter, Blastocatella, H16, Glomeromycota, and Aspergillus linearly increased with increasing salinization, suggesting that they could be used as bioindicators for salt-tolerant communities. Overall, the changes in the structures of soil bacterial and fungal communities were determined by the relative quantities of dominant taxa rather than community composition. The structures of soil bacterial and fungal communities were linked to soil properties and vegetation. Increasing soil salt content, and thereby varied pH and organic matter, were likely the direct influencing factors of microbial communities in these saline grasslands.

A TDR wireless device for volumetric water content sensing

Time Domain Reflectometry (TDR) is a widely used technique to estimate the soil volumetric water content (θ) and bulk electrical conductivity (σ). This paper presents TDR-WiFi, a wireless, portable and low cost interface to ease sensing of θ and σ by connecting TDR cable tester with a smartphone. TDR-WiFi consists of a microprocessor equipped with a WiFi microcontroller (M5Stack unit) and connected to the TDR device through an RS232-TTL adapter. The M5stack firmware is programmed in MicroPython language to act as a server between the user and the TDR device through a web page accessible from any smartphone web browser. TDR-WiFi is compatible with the Campbell TDR100 device and allows storing the TDR waveforms as well as estimating θ and σ. A complementary web page for subsequent analysis of the TDR waveforms was developed and is publicly available at http://swi.csic.es/tdrwifi/. The system was satisfactorily demonstrated in laboratory and tested in the field. The field trial allowed water content measurements in a steep road slope. TDR-WiFi demonstrated to be operative in the field and it can be satisfactorily used in difficult access areas.

Spatial and Temporal Variability of Soil Redox Potential, pH and Electrical Conductivity across a Toposequence in the Savanna of West Africa

Soil redox potential is an important factor affecting soil functioning. Yet, very few agronomy studies included soil redox potential in relation to soil processes. The objective of this study was to evaluate the spatial and temporal variation in soil redox potential and to determine the soil parameters affecting its variation. Soil redox potential, soil moisture, soil temperature, pH and bulk electrical conductivity were measured in upland rice fields during two growing seasons at six positions along an upland–lowland continuum, including two positions at the upland, two at the fringe and two at the lowlands in central Côte d’Ivoire (West Africa). The measurements were made at the following soil depths: 3, 8, 20 and 35 cm. Soil redox potential varied between 500 and 700 mV at the upland positions, 400 and 700 mV at the fringe positions and 100 and 750 mV at the lowland positions, and increased with soil depth. Variations in soil redox potential were driven by soil moisture, bulk electrical conductivity and soil organic carbon. We concluded that for proper interpretation of soil redox potential, sampling protocols should systematically include soil pH, moisture and bulk electrical conductivity measurements.

Field Comparison of Electrical Resistance, Electromagnetic Induction, and Frequency Domain Reflectometry for Soil Salinity Appraisal

By using different physical foundations and technologies, many probes have been developed for on-site soil salinity appraisal in the last forty years. In order to better understand their respective technical and practical advantages and constraints, comparisons among probes are needed. In this study, three different probes, based on electrical resistance (ER), electromagnetic induction (EMI), and frequency domain reflectometry (FDR), were compared during a field survey carried out in a large salt-threatened agricultural area. Information about the soil bulk electrical conductivity (σb) at different depths was obtained with each of the probes and, additionally, other soil properties were also measured depending on the specifications of each instrument and, moreover, determined in samples. On average, the EMI and FDR techniques could be regarded as equivalent for σb measurement, whereas ER gave higher σb values. Whatever the case, EMI, and also ER, had to be supplemented with information about soil clay, organic matter, and water mass fractions to attain, despite this effort, poor soil salinity estimations by means of multiple linear regression models (R2 < 0.5). On the contrary, FDR needed only probe data to achieve R2 of 0.7, though root mean standard error (RMSE) was still 1.5 dS m−1. The extra measurements and calculations that modern electrical conductivity contact probes integrate, specifically, those based on FDR, remarkably increase their ability for soil salinity appraisal, although there is still room for improvement.

Imaging plant responses to water deficit using electrical resistivity tomography

Background and aimsMonitoring root water uptake dynamics under water deficit (WD) conditions in fields are crucial to assess plant drought tolerance. In this study, we investigate the ability of Electrical Resistivity Tomography (ERT) to capture specific soil water depletion induced by root water uptake.MethodsA combination of surface and depth electrodes with a high spatial resolution (10 cm) was used to map 2-D changes of bulk soil electrical conductivity (EC) in an agronomic trial with different herbaceous species. A synthetic experiment was performed with a mechanistic model to assess the ability of the electrode configuration to discriminate abstraction patterns due to roots. The impact of root segments was incorporated in the forward electrical model using the power-law mixing model.ResultsThe time-lapse analysis of the synthetic ERT experiment shows that different root water uptake patterns can be delineated for measurements collected under WD conditions but not under wet conditions. Three indices were found (depletion amount, maximum depth, and spread), which allow capturing plant-specific water signatures based moisture profile changes derived from EC profiles. When root electrical properties were incorporated in the synthetic experiments, it led to the wrong estimation of the amount of water depletion, but a correct ranking of plants depletion depth. When applied to the filed data, our indices showed that Cocksfoot and Ryegrass had shallower soil water depletion zones than white clover and white clover combined with Ryegrass. However, in terms of water depletion amount, Cocksfoot consumed the largest amount of water, followed by White Clover, Ryegrass+White Clover mixture, and Ryegrass.ConclusionERT is a well-suited method for phenotyping root water uptake ability in field trials under WD conditions.

Spatial Variability of Soil and Plant Water Status and Their Cascading Effects on Grapevine Physiology Are Linked to Berry and Wine Chemistry.

The relationships between differences in plant water status, induced by spatial variability in soil texture, and the changes in berry and wine composition were investigated in an irrigated Cabernet Sauvignon (Vitis vinefera L.) vineyard for 2 years. A stratified and an equidistant grid were overlaid on the vineyard to characterize the soil texture by proximal sensing, soil sampling, and grapevine physiological and berry chemical development. Based on the mid-day stem water potential (Ψstem) integrals, the vineyard was divided into two functional homogenous zones: Zone 1 with higher water stress and Zone 2 with lower water. Zone 1 consistently had lower Ψstem, net carbon assimilation, and stomatal conductance in both years. Berry weight and titratable acidity were lower in Zone 1 at harvest. Zone 2 reached 26 and 24°Bx total soluble solids (TSS) at harvest in Years 1 and 2, respectively, with higher TSS values of 30 and 27°Bx in Zone 1. Ravaz index did not vary spatially. Fruits were harvested differentially in both years and vinified separately from the two zones. In Year 1, all berry skin anthocyanin derivatives, tri-, di- hydroxylated, and total anthocyanins concentrations were higher in Zone 2. However, in Year 2, only malvidin, tri-hydroxylated, and total anthocyanins were higher in Zone 1. There were no differences in wine flavonoids in Year 2 when harvest commenced earlier. In both years, Ψstem, berry weight, and TSS were directly related to soil bulk electrical conductivity (EC). Our results indicated vineyard variability stemmed from soil texture that affected long-term plant water status which does not affect spatial variability of Ravaz Index. In conclusion, our work provides fundamental knowledge about the applicability of soil bulk EC sensing in the vineyards, and its potential directional utilization by connecting proximal soil sensing to spatial distribution of whole-plant physiological performance together with berry and wine chemistry.

Biological soil crusts determine soil properties and salt dynamics under arid climatic condition in Qara Qir, Iran

Biological soil crusts are a thin layer within the soil system but strongly determine the infiltration, runoff and water and solute movement. Little is known about the role of biological soil crusts on soil solute dynamics in arid ecosystems and the objective of this paper is to determine in Qara Qir rangeland how biological soil crusts control the water and salt distribution along the soil profile. Rainfall simulation experiments were carried out at five locations, and measurements of the soil at 0–5, 5–10, 10–20, 20–30, 30–50 and 50–80 cm depth were done before, 48 h and 21 days after the rainfall simulations. Soil particle size distribution, bulk density, water content, organic carbon and electrical conductivity were measured at each of the 270 samples (3 seasons × 3 times × 5 sites × 6 depths). Biological soil crusts increased soil organic carbon, soil water content, and infiltration rate; and biological soil crusts decreased soil bulk density, clay fraction, electrical conductivity, and other saline-sodic properties, especially in the upper layers (0–10 cm). Large pores in soils covered by biological soil crusts enhanced the preferential flows, infiltration and solute transport. Biological soil crusts not only directly affected the soil surface, but also influenced soil properties, and consequently determined spatio-temporal soil salinity distribution. Biological soil crusts act as a soil salinity reducing agent and contribute to the soil quality improvement under arid climatic conditions. Biological soil crusts can be considered as a soil conservation strategy and actively used in soil rehabilitation and ecosystems restoration.

Coupled water flow, heat transport, and solute transport in a seasonally frozen rangeland soil

AbstractSoil water flow, heat transport, and solute transport in cold regions exhibit complex interactions that are difficult to quantify with measurements alone. For example, dissolved ions will lower the freezing point of soil water, while frozen soil will limit solute transport. In this study, a vertical one‐dimensional numerical model for coupled water flow, heat transport, and solute transport was combined with 8 years of Hydra impedance sensor monitoring data to estimate solute transport parameters in a high elevation, cool, semi‐arid mixed‐grass rangeland near Laramie, WY. Model calibration focused on the linear adsorption coefficient and the dispersivity in the solute transport equation. The brute force method was used to examine the complete parameter space using bulk soil electrical conductivity (σb) alone, and σb divided by tortuosity (τ) in the objective function. The use of σb yielded positive Modeling Efficiency (ME) for three out of five sensor depths (ME ≤ 0.49), while use of σbτ−1 yielded negative ME ≤ −0.01 for all depths. The low ME for σbτ−1 was expected as this ratio serves as a proxy for solute storage, which is expected to fluctuate relatively little with time for most terrestrial ecosystems. Reliable adsorption and dispersion coefficients could be determined for the 0–10 cm depth, and to a lesser extent, the 10–30 cm depth. At deeper depths, solute transport was only sensitive to the adsorption coefficient, so that reliable values for dispersivity could not be determined.

Exploring soil amendment strategies with polyacrylamide to improve soil health and oat productivity in a dryland farming ecosystem: One‐time versus repeated annual application

AbstractDegraded lands resulting from human and natural causes are widespread in arid and semiarid regions throughout the world. Polyacrylamide (PAM) soil amendments are increasingly used to remediate these degraded lands with the potential benefits on soil health and crop production. However, the scientific evidence of farm‐scale use of one‐time versus repeated application of PAM has not been reported. The specific objective of this research was to determine the effects of single versus multiple annual PAM application on (a) the dynamic changes in soil quality parameters and (b) oat crop productivity indicators in a dryland farming ecosystem. Our data illustrated that multiple years of annual application of PAM significantly increased soil profile water storage, whereas it reduced soil bulk density and electrical conductivity in the top (0–20 cm) and deeper layers (20–60 cm) over those for the control or single PAM application. The improved soil microecological environments led to increased activities of soil enzymes urease (up to 106%), invertase (94%), and catalase (45%). These in turn promoted soil nutrient turnover and availability (e.g., 76% higher soil alkaline N) and crop growth leading to the improvement in grain protein (up to 31%), protein yield (58%), and partial factor productivity of nitrogen (20%), than did the control treatment. Taken together, these soil and crop performance indicators suggest that repeated annual PAM application for a minimum of 2–3 years would be an effective strategy to combat drought and land degradation and foster sustainable crop production in dryland agriculture under a changing climate scenario.

Effect of Altitude on Forest Soil Properties at Northern Karakoram

This study aims to determine variation in soil physical, chemical and microbial properties along altitudinal gradients in fragile mountains region of the Karakoram. The soil samples were collected at the altitude ranging from 2787 to 3600 m from the alpine forest of the Bagrot valley, northern Karakoram, Pakistan and analyzed for various physical, chemical, and microbial parameters. The results indicate that there is a strong relationship of the soil parameters with altitude (p ≤ 0.01). With increasing elevation, soil bulk density, sand content, electrical conductivity (EC), pH, CaCO3 content, and 16S rRNA decreased significantly, while total porosity, saturation percentage, soil organic matter (SOM) contents, soil nutrients, and fungi-to-bacteria ratio increased with increasing altitude. These findings increase the understanding of dynamics of soil properties and enhance predictions of the responses of alpine soils to global warming.

Combined Effect of Poultry Manure and Soil Mulching on Soil Properties, Physiological Responses, Yields and Water-use Efficiencies of Sorghum Plants under Water Stress

ABSTRACTThe present investigation was planned to determine the effect of deficit irrigation, mulching and poultry manure application on sorghum grain, forage yield and water-use efficiencies. Two field experiments were conducted during 2016 and 2017 growing seasons at Demo farm, Fayoum, Egypt. Eighteen treatments comprising of two rates of rice straw as soil mulching (SM; zero and 10 ton per hectare), three irrigation treatments (I100% = 100%, I85% = 85% and I70% = 70% of crop evapotranspiration (ETc) and three poultry manure (PM) levels (0, 24 and 36 ton per hectare) were studied under controlled surface irrigation system. Sorghum growth attributes (plant height, stem diameter, leave area), grain and forage yield, water-use efficiencies (G-WUE and F-WUE) were significantly (p < .05) affected by irrigation quantity and both soil mulch and poultry manure application. Poultry manure resulted in a significant decrease in soil bulk density, electrical conductivity (ECe), soil pH, hydraulic conductivity and total porosity, useful pores, and water holding pores were increased. The results showed that underwater scarcity, application of (I85 × PM36× SM10) treatment was found to be favorable to save 15% of the applied irrigation water as compared to I100, at the time produced the same sorghum yields.

Effect of organic waste and aggregate sizes in some of soil physical properties, soil salinity and barley growth (Hordium vulgare L.)

Laboratory experiment was conducted to study the effect of three types of organic waste (chicken, sheep, Cows wastes ) and three different aggregate sizes (<2, <5, <10)mm on some soil physical properties, soil salinity and barley crop growth. The soil texture was clay loam. The soil samples were brought from north of Basrah governorate (Qurna district). The soil samples were dried in the air and then grinded. The soil samples were divided into three parts, one was passed through sieve of 2mm, the second through size of 5mm and the third through size of 10mm.The soils were distributed into plastic pots the amount of the soil was 2kg in each plastic pots the cows, sheep and chicken wastes were mixed with soil. The amount of the waste was 2% of the weight of the soil in each plastic pots the barley crop seeds (Hordium vulgare L.) were planted. The plastic pots were irrigated using tap water to the field capacity. The crop heights ware measured after two months of crop planting. The green and dry weights of the crop were measured after harvesting. The some soil physical properties were also measured namely aggregate stability which expressed as mean weight diameter (MWD), aggregate index, bulk density, total porosity, saturated hydraulic conductivity and electrical conductivity. The results showed that the organic wastes significantly affected (improved) MWD, aggregate index, bulk density, total soil porosity, crop height and wet and dry weight of the crop green part. The values of the above parameters are 0.548mm, 0.395, 1.435 Mgm−3, 43.51%, 38.908cm, 14.41 g pots−1 and 2.592g pots−1 respectively compared with control treatment. While the organic wastes did not significantly affect the soil saturated hydraulic conductivity and soil electrical conductivity. The chicken waste gave the highest MWD, aggregate index, total porosity, crop height and the wet and dry weight of the green part of the crop. The percentage of increased are 59.169, 64.890, 15.568, 16.000, 74.140 and 113.671% respectively, whereas the soil bulk density decreased by 9.730% compared with control treatment respectively. The results also showed the soil aggregate sizes significantly affected the aggregate index, soil bulk density, soil total porosity, soil electrical conductivity and crop growth, whereas it did not significantly affect MWD, soil saturated hydraulic conductivity. 2mm aggregate surpassed the other aggregates (5 and 10mm) in recording the height values for the above parameters except, soil bulk density and soil electrical conductivity which they decreased with 2mm aggregate.