Electrical Conductivity Of Saturated Extract Research Articles

Effects of Applying Sewage Sludge Treated with Amendments on Soil Chemical Properties

ABSTRACT Soil application of treated sewage sludge is considered a beneficial management option for agriculture and environment. Sludge treated with clay minerals or biochar was evaluated as soil amendment, in comparison with limed or untreated sludge. Bentonite, vermiculite, biochar or lime was added to dewatered sewage sludge at 0 and 15% rates, in three replications and air-dried. Then, the treated and untreated sludge were added to two soils, one acid and one alkaline, at 0 (control), 1 and 3% rates, in three replications. The results showed that the pH of acid soil significantly increased compared to control upon addition of treated and untreated sludge at both rates, but remained acidic (<6.0) in all cases except for limed sludge. Upon addition of 3% treated or untreated sludge to both soils, organic carbon (OC) significantly increased compared to control. The same stands for soil available ammonium nitrogen (NH4-N), phosphorus (P), potassium (K), copper (Cu), zinc (Zn) and boron (B) for both soils and rates. Soil total heavy metals, which regulate sludge’s agronomic use, were below the legislative limits. However, the 3% addition rate of all kinds of sludge, especially of untreated, to both soils increased the electrical conductivity of saturation extract (ECse >2 dS m−1) at unacceptable levels for sensitive crops and available P, B and Zn 2–3, 2–4 and 6–12 times above the initial, respectively. Consequently, sewage sludge treated with bentonite, vermiculite or biochar could be used as a soil amendment but at rates lower than 3% (≈120 Mg ha−1).

Salinity-specific stomatal conductance model parameters are reduced by stomatal saturation conductance and area via leaf nitrogen

Modeling stomatal behavior is necessary for accurate stomatal simulation and predicting the terrestrial water‑carbon cycle. Although the Ball-Berry and Medlyn stomatal conductance (gs) models have been widely used, variations and the drivers of their key slope parameters (m and g1) remain poorly understood under salinity stress. We measured leaf gas exchange, physiological and biochemical traits, soil water content and electrical conductivity of saturation extract (ECe), and fitted slope parameters of two genotypes of maize growing in two water and two salinity levels. We found m was different between the genotypes, but no difference in g1. Salinity stress reduced m and g1, saturated stomatal conductance (gsat), the fraction of leaf epidermis area allocation to stomata (fs), and leaf nitrogen (N) content, and increased ECe, but no marked decrease in slope parameters under drought. Both m and g1 were positively correlated with gsat, fs, and leaf N content, and negatively correlated with ECe in the same fashion among the two genotypes. Salinity stress altered m and g1 by modulating gsat and fs via leaf N content. The prediction accuracy of gs was improved using salinity-specific slope parameters, with root mean square error (RMSE) being decreased from 0.056 to 0.046 and 0.066 to 0.025 mol m−2 s−1 for the Ball-Berry and Medlyn models, respectively. This study provides a modeling approach to improving the simulation of stomatal conductance under salinity.

Maize is stressed by salt rather than water under drip irrigation with soil matric potential higher than −50 kPa in an arid saline area

AbstractWater scarcity and soil salinization are the top abiotic stresses impeding agricultural production in arid and semi‐arid regions. To evaluate maize growth is depressed by water stress or salt stress independently as well as in combination under drip irrigation, a 3‐year field experiment was conducted in the Hetao Irrigation District, north‐west China. The soil was moderately saline with ECe (electrical conductivity of saturated extract) of 7.1 dS/m. Five threshold values of soil matric potential (SMP): −10 kPa (S1), −20 kPa (S2), −30 kPa (S3), −40 kPa (S4), and −50 kPa (S5), were used to trigger a 10‐mm drip irrigation. With triplicate for each treatment, 15 plots were arranged in a randomized block design permanently during the experimental period. Results showed that the higher SMP facilitated the formation of low‐salinity zone. The water holding depths in root zone were generally above the refill point (threshold of readily available water, 0.23 cm3/cm3 for maize) during the growing seasons for all treatments, indicating maize could extract water easily from soil. Controlling SMP &gt; −30 kPa (S1, S2, S3) produced the higher leaf area index, specific leaf area, biomass and grain yield significantly than S4 and S5; however, no significant difference in relative chlorophyll contents was detected among treatments. Grain yield was reduced by 6.8% per dS/m increase in soil ECe beyond salt tolerance of maize. Based on the soil readily available water for maize growth, crop's responses and data analysis, it could be concluded that salt stress, rather than water stress, was the key factor causing the reduced grain yield in this study. Taking into account the grain yield and water‐use efficiency, SMP threshold of −30 kPa was recommended for drip irrigation maize in this saline soil. These findings are conducive to the extension of drip irrigation, and increasing the resilience of crop production under the arid saline condition.

Reclamation of a calcareous sodic soil with combined amendments: interactive effects of chemical and organic materials on soil chemical properties

Concerns about population growth and producing adequate and nutritious food from the limited available resources have made soil conservation a top priority worldwide. This study assessed the effects of alfalfa residue (AR), sugarcane-bagasse biochar (SBB), and walnut-shell biochar (WSB) with or without gypsum (G), aluminum sulfate (AlS), and mixture of both chemical amendments on the chemical properties of a carbonated sodic soil. The organic and chemical ameliorants were added to the soil at rate of 2.5% (w/w) and the soil gypsum requirement, respectively. After a 4-month incubation, amended soils were measured for pH, electrical conductivity of saturated extract (ECe), sodium adsorption ratio (SAR), and exchangeable potassium (K) and available phosphorus (P) concentrations. Both chemical and organic amendments significantly lowered soil pH through enhancing CO2 partial pressure and/or dissolution of native soil calcites. The combined chemical and organic amendments performed more effectively than organics alone to increasing soil EC; the highest EC value was obtained by the application of G+AR (11.0 dS m−1). A synergistic effect of organic and chemical ameliorants on the replacement of exchangeable sodium by calcium was observed, which was reflected by the increased SAR values in treated soils compared with the control. Of the applied amendments, AR-alone has the best efficacy to improve soil available P by enhancing soil P concentration from 4.05 mg kg−1 in the control to 11.87 mg kg−1. Irrespective of chemical amendments, the most increase in soil exchangeable K concentration (from 45.16 mg kg−1 in the control to 274.00 mg kg−1) was obtained by applying WSB-alone to the soil. These results suggest that the partly degraded sodic soils could evolve for agricultural use by amending soils with specific kind of biochars and combined with best soil management practices.

Melon cultivation irrigated with saline waters promote chemical alterations in an acrisol

The objective of the present study was to evaluate the salinization process and the changes in the chemical properties of an Acrisol cultivated with melon irrigated with water of different saline concentrations. The experiment was carried out in the field conditions using the experimental design of randomized blocks, arranged in split-plot. The plots were composed of salinity levels of irrigation water, expressed in terms of water electrical conductivity (ECw): 0.54; 1.48; 2.02 dS m-1; and the sub-plots for melon cultivars: Sancho and Medellín (Toad Skin), Mandacaru (Yellow), Nectar (Galia) and Sedna (Cantaloupe). Soil samples were collected at the beginning and end of the crop cycle to evaluate the changes in the physical-chemical properties of the soil. The electrical conductivity of saturation extract in the soil profile varied for each cultivar, observing high salinity values in soils with cultivars with lower water demand (Sedna and Nectar). The salinity of the soil was lower than the electrical conductivity of the irrigation water in the treatments with high values of ECw. The soil pH values showed little reaction in relation to the initial values. The exchangeable sodium percentage values were approximate twice the sodium adsorption ratio of the saturation stratum.

Effect of potassium and mulching ameliorants on soil enzyme activities in peanut (Arachis hypogaea) crop facing salinity stress

Salinity in agriculture creates a menace when exceeds the threshold limit, impacting heavily both soil and plants grown on it. K-fertilizer and mulching are often proposed to control salinity. In this backdrop, our study was aimed to analyze the effect of four important soil enzymes by combined application of muriate of potash as potassium fertilizer (control, 30, 60 kg K ha-1) and mulching (with and without polythene mulch) under saline irrigation (control, 2.0, 4.0dS m-1) during the active crop growth stages (50 and 100 DAS) in peanut (Arachis hypogaea L.) crop during summer, 2014. Results revealed that polythene mulching could effectively reduce the electrical conductivity of saturation extract of soil (ECe) across the salinity levels. The differentiating effects under mulching and potassium treatments were also observed for each of the enzymes studied. Dehydrogenase, alkaline phosphatase and urease enzymes recorded more activity at 100 DAS than 50 DAS, while acid phosphatase showed a reverse trend. However, the benefits of using ameliorants like mulching and potassium fertilizer for soil biological activity under peanut crop were found to be salinity treatment specific, either at higher irrigation salinity (4.0 dS m-1) or at non-saline or lower irrigation salinity (2.0 dS m-1) plots. To reduce the impact of salinity both the ameliorants may or may not act jointly as observed in the present study. Overall, our study inevitably established the usefulness of mulching and potassium fertilizer for sustenance of soil biological health under salt-prone arid and semi-arid regions.

Development of secondary salinity and salt migration in the irrigated landscape of hot arid India

The present paper examines the nature of salt movement by the influence of landscape position and development of secondary salinity in Indira Gandhi Nahar Pariyojana command area of hot arid India. Soil samples were collected along 20 km transect across landscapes of upland, medium land, lowland and wetland. Soil properties, electrical conductivity of saturated extract (ECe), soluble ions in saturated extracts, exchangeable sodium percentage (ESP) and sodium adsorption ratio were determined. Results showed that cation exchange capacity, organic carbon and CaCO3 were significantly increased in lowland and wetland while soil pH, salinity indicators (ECe and ESP) and exchangeable cations and anions such as chloride and sulphate were increased significantly (P < 0.05) in the wetland. The mean exchangeable Na was increased while exchangeable Ca, Mg, and K decreased from upland to wetland landscape. It was found that Cl− imposed an existing and potential threat to sensitive crops in medium to wetland, where Cl− concentrations were greater than 106 me L−1. Principal component analysis helped in the identification of the parameters responsible for soil salinity variation, and the first factor indicated that soil ECe and ESP had a major role in the development of salinity and sodicity, respectively. Cluster analysis grouped four sampling sites into three clusters and members of the third cluster (lowland and wetland) were in close proximity. Under the prevalent arid conditions, improving the management of irrigation water should be the indispensable one to conserve and sustain the already fragile agricultural soils in the hot arid regions of India.

Physio-chemical properties and dynamic of the surface sediment in riparian mangroves along the Tien river, Tien Giang province

This study was conducted to investigate the physio-chemical properties and vertical dynamic of the surface sediment (0–5 cm) in riparian mangroves along the Tien river, Tien Giang province. The distribution of riparian mangroves located from the polyhaline zone (transect S1 and S2) to the mesohaline zone (transect S3 and S4) and the oligohaline zone (transect S5). Three plots (10x10 m) per transect were set based on the elevation of the mangrove floor (cm + mean sea level) and dominant plants. A total of 28 sediment samples were collected in December 2016 and April 2017. Seasonal variation of pH, redox potential (Eh), electrical conductivity of saturated extract (ECse), bulk density, sediment organic matter (SOM) and total sulfur (TS) were measured in accordance with the standard protocols. Seasonal trends of vertical erosion and accumulation were tested by the tracer stick method. The ECse values and TS concentrations were higher in the dry season and in transects closed to the estuary (S1, S2 and S3) but these trends weren’t found for pH, Eh, and SOM. In most of the riparian mangroves along the Tiền river, low elevation (0–50 cm) was one of important factors affecting the Eh and ECse. In the rainy season, major changes in vertical erosion and acumulation have occurred in the transects near the mouth of the river.

Characterization and Formation of Salt affected Soils in Eastern Rajasthan Upland

Soils of the Bhilwara district are affected with different degree and extent of soluble salts. These soils are distributed in hot semi-arid agro-ecological sub region of Rajasthan. It is located between 25o 01' to 25o 58' N latitude and 74o 01' to 75o28' E longitude at an elevation between 380 and 500 meters above the mean sea level. The physico-chemical analysis of soils revealed the dominant cations such as sodium followed by calcium. Exchangeable sodium percentage was ranged 23.1 to 54.6, 17 to 38.5 and 7.1 to 20.0 in saline, sodic and saline-sodic soils, respectively. The Sodium Adsorption Ratio varied from 2.5 to 16.8, 3.2 to 9.4 and 3.8 to 12.6 in these problematic soils, respectively. Soil reaction was ranged from 7.6 to 8.4, 8.5 to 9.3 and 8.5 to 8.8 whereas electrical conductivity of saturation extract varied from 14.4 to 25.2, 1.0 to 5.6 and 2.4 to 13.6 dSm-1 in saline, sodic and saline-sodic soils, respectively. Area under saline and saline-sodic soils was moderately-well to well drained whereas sodic soils were imperfectly drained. Accumulation of calcium carbonate showed increasing trend with depth of profile in all three soils. Mean values of adjusted sodium adsorption ratio of irrigation water was 43.55, 41.88 and 36.74 for saline, saline-sodic and sodic soils. Use of low quality underground water for irrigation, aggravated the process of formation of the salt affected soils in eastern Rajasthan Uplands.

Effect of the micro-sprinkler irrigation method with treated effluent on soil physical and chemical properties in sea reclamation land

To develop a micro-sprinkler method with treated effluent for tall fescue (Festuca arundinacea) cultivation in sea reclamation land and test its effect on soil physical and chemical properties, a field experiment with five treatments of water quality was conducted in 2015–2016. The five treatments of water quality were created with a mixture of treated effluent (EC, 4.2–6.9 dS/m) and fresh groundwater, and the percentage of treated effluent was 0%, 25%, 50%, 75% and 100%. Saline soil contained a gravel-sand layer imbedded at depth of 60 cm. Irrigation management was divided into three stages, enhanced salt leaching stage (continuous irrigation), water-salt regulation stage (irrigation based on the soil matric potential (SMP) at −5 KPa) and normal irrigation stage (irrigation based on the SMP at −20 KPa). The results indicated that the first stage lasted for 10 days, while the electrical conductivity of saturated extracts (ECe) of the surface 10 cm from 38.29 dS/m dropped to 4.23–6.28 dS/m. After the second stage (3.5 months), the ECe in the 0–60 cm soil layer dropped to 1.42–3.16 dS/m. During these stages, treatment with 50% treated effluent led to relatively good infiltration and lower salinity and was therefore good at enhancing the salt leaching efficiency. In the third stage, the observed ECe of the 0–60 cm changed slightly, but ≤75% treated effluent could maintain the soil salinity below the threshold salinity of tall fescue, even in the rainless season. During the process, soil sodium adsorption ratio decreased, while soil pH increased first and then decreased. Soil available phosphorus content showed a close correlation with treated effluent and the biomass of tall fescue. Moreover, the tall fescue maintained normal growth. Therefore, it is possible to use treated effluent to micro-sprinkler irrigation on tall fescue in sea reclamation land.

Soil physicochemical properties and their significance for sustainable sugarcane production in Kesem Allaideghe plains irrigation project area, Eastern Ethiopia

A feasibility study was carried out to assess the suitability of Allaideghe plains, located in middle awash valley, for the cultivation of sugarcane plantation. The project area, covering 38000 ha, lies between 9o 07’ to 9o 26’ N latitude and 40o 30’ to 40o 50’ E longitude. A detailed soil survey was carried out on 500 m x 500 m grid consisting 1520 auger holes and 76 soil profile observations. The soils of the entire project area were very deep (&gt;200 cm). The textural classes included silty clay loam, clay and heavy clay which revealed that texture varied from fine to very fine with high clay content. Soil reaction (pH), electrical conductivity of saturated extract (ECe), exchangeable sodium percentage (ESP), cation exchange capacity (CEC), organic carbon (OC), CaCO3 ranged between 7.7 to 8.2, 0.9 to 8.0 dS m-1, 9.9 to 42.7%, 40.6 to 61.7 cmol (+) kg-1, 0.3 to 1.2 g kg-1, and 8.3 to 18.3 %, respectively. Soluble cation contents of Na, Mg, Ca and K varied from 8.5 to 20.2, 0.2 to 2.6, 4.7 to 12.6, and 0.1 to 0.2 meq l-1, respectively. Major hydraulic properties influencing water availability and irrigation scheduling for sugarcane included infiltration rate and hydraulic conductivity. Basic infiltration rate varied from 0.2 to 6.2 cm h-1 and in-situ hydraulic conductivity varied from 0.07 to 0.60 m d-1. Low hydraulic conductivity may cause waterlogging in the project area. In order to improve soil structure and water availability, addition of gypsum, plant residues and organic matter are recommended.Keywords: Soil survey, physical and chemical soil properties, infiltration rate, hydraulic conductivity

Field-scale Spatial Variability of Electrical Conductivity of the Inland, Salt-affected Soils of Northeast Thailand

Salt-affected soil maps for Northeast Thailand focus on the percentage of salt crusts. Investigation was done to find the field-scale spatial variability of the electrical conductivity of saturation extract (ECe) in salt-affected areas (percentage salt crusts: very severely = class 1; severely = class 2, and moderately = class 3). Two study sites were selected for each class (n = 6). Soil samples (n = 100) were collected at each site using stratified, systematic, unaligned sampling, and analyzed for ECe. Variations in ECe were assessed using basic statistics and geostatistics. At the field-scale, in every class, the best-fit semivariogram model generated was satisfactory (R2 &gt; 0.8). Interpretation from the relevant model parameters (i.e., nugget, sill, and effective range), together with the interpolated (kriged) maps, demonstrated that the characteristics of spatial variability of soil ECe were inconsistent, even between different sites of the same salt-affected soil class. In general, various degrees of small-scale variation were observed, very high variation of ECe was common, spatial dependence was strong to moderate, while the spatial distribution pattern was in distinctive patches. The size of patches depended on the effective range at each site. This study also revealed that the class 1 areas were entirely, very strongly saline (ECes range, 56.70 and 433.00 dS·m-1), whereas the areas of class 3 were non-saline to moderately saline (range, 0.11 - 5.26 dS·m-1). Class 2 areas were much more complex; the soils varied from non-saline to very strongly saline (range, 0.16 - 49.00 dS·m-1). Information on the nature and characteristics in the spatial variability of soil ECe is useful for developing strategies for management of salt-affected soils in precision agriculture in this region.

Ring diameter effects on determination of field-saturated hydraulic conductivity of different loam soils

Establishing ring diameter effects on the field-saturated soil hydraulic conductivity, Kfs, determined with ponding infiltrometer methods can help to find a compromise between the need to sample a large area with an individual measurement and the impracticality of using large rings in the field. Five ring sizes (diameter, D=5.5, 10.9, 16.0, 27.8 and 31.8cm) were used to determine Kfs by the simplified falling head (SFH) technique in four loamy soils with different salinity (electrical conductivity of saturated extract, ECe=0.9–29.4dS/m) and sodicity (exchangeable sodium percentage, ESP=2.7–81.3%) levels. According to USDA classification, two soils were non-saline, non-sodic (NN1 and NN2), a soil was saline-sodic (SS) and another soil was non-saline and sodic (NS). Ring diameter did not have in general a statistically detectable influence on the mean Kfs of a given soil. The only exception was for the NS soil but also in this case the effect was negligible for many practical applications since Kfs increased by 2.3 times as D increased from 5.5 to 31.8cm. However, smaller rings implied either higher or lower estimates of Kfs variability as compared with larger rings, depending on the soil. The former result probably occurred when only a part of total heterogeneity was sampled with a small ring. The latter result was probably obtained when insertion of small rings altered or even destroyed the fragile macroporosity and also when using small rings increased the probability to only sample relatively homogeneous soil volumes. As compared with the largest rings, those with a diameter in the range 10.9 to 27.8cm yielded a similar information on the differences between the soil hydraulic conductivity of the four considered soils. More discrepancies were detected for the smallest rings (D=5.5cm). Even small rings appear usable to obtain a mean value of Kfs for the sampled soils, perhaps with the exception of the smallest ones. However, as large as possible rings should be used if Kfs variability has also to be determined.

English

In the Cuvelai Seasonal Wetland System (CSWS) of North-central Namibia, there are widespread manifestations of seasonally flooded river and seasonally closed wetland ecosystems (ponds). These wetlands are called oshana (seasonally flooded river wetland) and ondombe (seasonally closed wetland) according to the local language. This study was initiated to find out the soil fertility status of ondombes and whether they could be utilized for agricultural purposes unlike the present situation. Soil salinity and sodicity were determined to find out impact of such adverse conditions on possibility of food production. A total of 70 representative ondombes were identified from three selected villages. A total of 210 soil samples were collected from upper, middle and lower positions adjacent to ondombes, and 15 soil samples from each 5 upland fields in the three villages and 102 soil samples from different spots of the flood plain in the three oshanas for comparison. The results indicated that the mean soil pH (H2O) in ondombe was 6.3, the means of organic C and total N were 6.28 and 0.41 g kg-1; respectively, the mean of available P was 4.81 mg P kg-1. The means of exchangeable Ca, Mg, K, and Na in ondombe were 2.31, 1.44, 0.21, and 0.61 cmolc kg-1, respectively. Most soil nutrients were higher in lower ondombe positions than on upper and middle positions. Organic C, exchangeable Mg, and clay at the ondombe soils were significantly higher than those at the croplands. The means of electrical conductivity of saturation extract (ECe) and sodium adsorption ratio (SAR) in ondombe soils were 0.62 ds m-1 and 7.32, respectively; even though most of the ondombe soils did not exhibit salinity and sodicity problems. Hence, one can conclude that an ondombe soil has an appropriate condition for agriculture, and may only be prone to sodicity whenever the sodium content is high, as sometimes observed. &nbsp; Key words: Soil fertility, seasonal wetland, soil salinity, sodicity, Cuvelai Seasonal Wetland System (CSWS).

Amelioration of saline–sodic soil with gypsum can increase yield and nitrogen use efficiency in rice–wheat cropping system

ABSTRACTA 2-year field experiment was conducted to determine crop yield and N use efficiency (NUE) from a saline–sodic soil (clay loam) with and without application of gypsum. Treatments included two N application rates (15% and 30%) higher than the recommended one to the normal soil, and gypsum added at 50% and 100% of soil gypsum requirement (SGR) to the saline–sodic soil, both cultivated with rice and wheat during 2011–2013. Results revealed a decrease in pH of saturated soil paste (pHs), electrical conductivity of saturation extract (ECe), sodium adsorption ratio (SAR) and exchangeable sodium percentage with N fertilizer along with gypsum application in saline–sodic soil. However, the effect was most prominent when gypsum was added at 50% of SGR. Crop yield and NUE remained significantly lower (p < 0.05) in saline–sodic-soils as compared to normal soil. However, gypsum application reduced this difference from 47% to 17% since both yield and NUE increased considerably. Crop yield and NUE remained higher for wheat than for rice. During first year, higher doses of N with gypsum application at 50% SGR proved most effective, whereas, in subsequent year, recommended N along with gypsum at 50% SGR became more profitable. All these results lead us to conclude that gypsum application can ameliorate saline–sodic soil thereby increasing crop yield and NUE.

Evaluating performance of macroscopic water uptake models at productive growth stages of durum wheat under saline conditions

Water management in agricultural lands largely depends on quantity and quality of available soil and water resources. In arid and semi arid regions, scarcity of fresh water and soil salinity are two main important limiting factors for crop production. Under such limiting conditions, one practical alternative for crop production is the use of unconventional or brackish water. If used, the quantitative response of plants to salinity must be carefully analyzed by means of modeling. On the other hand, plant response to salinity varies under different growth stages. Durum wheat (Triticum turgidum L.) is an important crop cultivated in some arid and semi-arid areas across the world such as Middle East and North Africa. This study was aimed to quantitatively characterize the Durum wheat response to salinity under different productive growth stages. Consequently, a large experiment in natural saline sandy loam soil (Typic Toriorthent) with five natural saline water treatments including 2, 4, 6, 8 and 10 dS/m each with three replicates was conducted. Furthermore, four predictive linear and nonlinear models of Maas and Hoffman, van Genuchten and Hoffman, Dirksen et al. and Homaee et al. were evaluated to predict relative transpiration and relative yield of durum wheat under heading and ripening growth stages. Three statistics including modified coefficient efficiency (E'), modified index of agreement (d') and coefficient of residual mass (CRM) were used to compare the used models and to assess their performances. Results indicated that among the examined models, the macroscopic model of Homaee et al. can provide more reasonable predictions at heading stage, while the piece-wise linear model of Maas and Hoffman provided slightly better prediction at ripening growth stage. The obtained threshold value and slope of reduction yield were quite different from those previously reported in the literature. These findings reveal that the widely cited tables describing the relationship between relative yield and electrical conductivity of saturated extract, averaged over the root zone as well as the entire growing season, are quite approximate and carry significant uncertainty. More experimental studies are still needed to obtain reliable data under different growth stages.

Visible-Near Infrared Reflectance Spectroscopy for Rapid Characterization of Salt-Affected Soil in the Indo-Gangetic Plains of Haryana, India

Management of salt-affected soils is a challenging task in the input intensive rice-wheat cropping zone of the Indo-Gangetic plains (IGP). Timely detection of salt-affected areas and assessment of the degree of severity are vital in order to narrow down the potential gap in yield. Conventional laboratory techniques of saturation extract electrical conductivity (ECe) and sodium adsorption ration (SAR) for soil salinity assessment are time-consuming and labour intensive; the VNIR (visible-near infrared) reflectance spectroscopy technique provides ample information on salinity and its attributes in an efficient and cost-effective way. This study aims to develop robust soil reflectance spectral models for rapid assessment of soil salinity in the salt affected areas of the IGP region of Haryana using VNIR reflectance spectroscopy. The results indicated that the spectral region between 1390 and 2400 nm was highly sensitive to measure changes in salinity. The developed hyperspectral models explained more than 80 % variability in ECe, and other salinity related attributes (saturated extract Na+, Ca2+ + Mg2+, Cl− and SAR) in the validation datasets. With the increasing availability of data from hyperspectral sensors in near future, the study will be very useful in real time monitoring of soils in the spatio-temporal context; enabling the farmers of IGP area to deal with salt degradation more effectively and efficiently.

Characterization of soils of Ghataprabha Left Bank Canal commandarea of north Karnataka for salinity and sodicity

A study was conducted to characterize soil salinity and sodicity of Ghataprabha Left Bank Canal command area of Mudhol taluk (Bagalkot District). Bulk Electrical conductivity of salt affected soils was determined by using electromagnetic induction (EM 38). The pHs of surface and sub-surface soil layers ranged from 7.4 to 8.7 and 7.7 to 8.6, respectively. Electrical conductivity of saturated extract of surface and sub-surface soils ranged from 4.2 to 59.9 dSm-1 and 4.2 to 57.0 dSm-1. Majority of soil samples were found to be saline as sodium absorption ratio (SAR) ranged between 0.3 to 10.8 and 0.5 to 10.9 for surface and sub-surface soil, respectively. Among the analysed surface soil samples, 26 per cent were saline, 18 per cent sodic and 56 per cent were saline-sodic. On the other hand, 26, 20 and 54 per cent of soils were categorized into saline, sodic and saline-sodic, respectively. Among the water soluble cations, Na+ (10.9 to 73.4 cmol (P+) kg-1) pre-dominated in surface and sub-surface horizons (10.9 to 65.2 cmol (P+) kg- 1). Among water soluble anions, Cl- dominated both in surface (2.0 to 60 me L-1) and sub-surface (2.0 to 59.0 me L-1).

Use of geophysical survey as a predictor of the edaphic properties variability in soils used for livestock production

The spatial variability in soils used for livestock production (i.e. Natraquoll and Natraqualf) at farm and paddock scale is usually very high. Understanding this spatial variation within a field is the first step for site-specific crop management. For this reason, we evaluated whether apparent electrical conductivity (ECa), a widely used proximal soil sensing technology, is a potential estimator of the edaphic variability in these types of soils. ECa and elevation data were collected in a paddock of 16 ha. Elevation was negatively associated with ECa. Geo-referenced soil samples were collected and analyzed for soil organic matter (OM) content, pH, the saturation extract electrical conductivity (ECext), available phosphorous (P), and anaerobically incubated Nitrogen (Nan). Relationships between soil properties and ECa were analyzed using regression analysis, principal components analysis (PCA), and stepwise regression. Principal components (PC) and the PC-stepwise were used to determine which soil properties have an important influence on ECa. In this experiment elevation was negatively associated with ECa. The data showed that pH, OM, and ECext exhibited a high correlation with ECa (R2=0.76; 0.70 and 0.65, respectively). Whereas P and Nan showed a lower correlation (R2=0.54 and 0.11 respectively). The model resulting from the PC-stepwise regression analysis explained slightly more than 69% of the total variation of the measured ECa, only retaining PC1. Therefore, ECext, pH and OM were considered key latent variables because they substantially influence the relationship between the PC1 and the ECa (loading factors&gt;0.4). Results showed that ECa is associated with the spatial distribution of some important soil properties. Thus, ECa can be used as a support tool to implement site-specific management in soils for livestock use.

Earthworm activities increase the leaching of salt and water from salt-affected agricultural soil during the wet–dry process under simulated rainfall conditions

The objectives of this study were to (1) evaluate earthworm-induced leaching of water and salt from salt-affected agricultural soils with constant and fluctuating soil moisture conditions and (2) determine the effects of earthworms on the distribution of soil salt in casts, burrow walls, and surrounding soils responsible for salt leaching. Soils were kept in mesocosms at constant moisture (CM) or underwent one wet–dry process (WD). Each soil moisture treatment had three earthworm treatments, including (1) inoculation with high abundance of earthworms (five endogeic Aporrectodea trapezoides), (2) inoculation with moderate abundance of earthworms (three endogeic A. trapezoides), and (3) no earthworm treatment. The presence of earthworms significantly increased total leaching water volume compared to the same treatment without earthworms in both moisture treatments. In the treatment following the wet–dry process, more than 65 % of water leaching occurred during the rainfall event, whereas in the treatment following constant moisture, more than 60 % of water leaching occurred after the rainfall event. The presence of earthworms produced a higher salt amount in the leaching water than the same moisture treatment without earthworms, but only the low number of earthworms (three endogeic A. trapezoides) caused a significantly higher total amount of leached salt than the same moisture treatment without earthworms. The percentage of leached salt in leaching water during the rainfall event ranged from 75.31 to 79.93 % in the wet–dry treatment and from 41.28 to 50.65 % in the constant moisture treatment. The wet–dry process significantly increased the total amount of leached salt from salt-affected agricultural soil compared to the constant moisture treatment when earthworms were present, which may be due to the significantly higher electrical conductivity of saturation extract (ECe) of earthworm casts than those of burrow walls and surrounding soils in the 0- to 10-cm soil layer.