High Exchangeable Sodium Percentage Research Articles

Nutrient status and production of fodder beet irrigated with saline-sodic water in Mediterranean calcareous soils

ABSTRACT The impact of drip irrigation with saline-sodic water on the nutrient status and productivity of fodder beet (Beta vulgaris) was evaluated in rainy and dry Mediterranean cropping seasons. Two field experiments were conducted during two growing seasons (winter and summer) in calcareous soil (31% CaCO3) of Sais area, Northwestern Morocco. The rainfall was 337 mm for winter and 53 mm for summer. Four salinity levels of irrigation water (ECi) were investigated: control (1ds m−1), 4, 6, and 10 ds m−1. The ECi levels were prepared by adding sodium chloride (NaCl, laboratory grade, 99.5%) to water. The results showed that the soil salinity (ECs) was related to the growing season and the irrigation water salinity (ECi). The depressive effect of salinity on the whole plant dry biomass (−25% as average) was observed only in the summer crop cycle at different ECi ≥ 4 ds m−1 compared to control. The plant NaCl uptake for both seasons could be predicted by a linear model: Y (kg ha−1 of NaCl) = 36.3 ECi + 23.6 Q − 101.3 (adjusted R2 = 0.88) where Q = total dry biomass (t ha−1). Saline-sodic irrigation water reduced the contents of boron, calcium, and magnesium in the plants. The exchangeable sodium percentage (ESP) in the soil exceeded 41% at ECi ≥ 4 ds m−1 for both seasons. The study demonstrated that fodder beet escapes the negative impact of salt stress in the rainy season. However, the high ESP recorded at harvest did not reveal the efficacy of fodder beet in NaCl removal from the soil.

Effect of Different Levels of Sodicity on Soil Enzymes, Soil Microbial Biomass Carbon and Activity of Antioxidant Enzymes in Different Rice Varieties under Semi-arid Conditions

Background: Soil sodicity is a major abiotic stress for crop production in many parts of the world. Soil enzymes have been proposed as potential indicators of soil quality due to their connection to soil biology, ease of measurement and quick responsiveness to changes in soil management. Concerning that how different levels of sodicity affects the activity of soil enzymes, soil MBC and antioxidant enzymes in different rice varieties will promote us to understand the mechanism behind the tolerant varieties and to find out the ways to improve the tolerance mechanism. Methods: A field experiment was conducted at Anbil Dharmalingam Agricultural College and Research Institute, Tiruchirappalli, Tamil Nadu during late samba season. Different rice varieties viz., TRY 1, CO 43, TRY 2, CSR 27, TRY 3 and white ponni (WP) were grown at different levels of Exchangeable Sodium Percentage (ESP) ie., 8, 16, 24, 32, 40 and 48 under field condition. The soil samples were collected at flowering stage and analyzed for urease, alkaline phosphatase (APH), dehydrogenase (DHG) and soil microbial biomass carbon (MBC). The plant samples collected at flowering stage were examined for activity of antioxidant enzymes like catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD). Result: The growth and yield decreases with increasing sodicity levels. The soil enzyme and microbial biomass carbon found to be decreased with increasing ESP levels. The antioxidant enzyme increases with increase in sodicity levels in tolerant varieties and decreases at high ESP levels in susceptible varieties. Overall TRY 3 outperformed under increasing sodicity levels compared to other varieties.

Plant-available water capacity of soils at a regional scale: Analysis of fixed and dynamic field capacities

Estimation of the plant-available water capacity (PAWC) of soils at a regional scale helps in adopting better land use planning, developing suitable irrigation schedules for crops, and optimizing the use of scarce water resources. In the current study, 72 soil profiles were sampled from the Barossa region of South Australia to estimate pedo-transfer functions deduced from easily estimated soil properties. These functions were then used to estimate the fixed (10 and 33 kPa) and dynamic pressure head (hfc) water contents at field capacity (FC) for minimum drainage flux (0.01 and 0.001 cm d-1), which serves as the upper boundary for plant-available water in soils. The estimated residual water content was corrected for subsoil constraints, especially the exchangeable sodium percentage (ESP). The results showed that the mean values of hfc in sand-dominated light and medium textured soils (i.e., sand, loamy sand, sandy loam, and loam) varied in a narrow range (15.8–18.2 kPa), whereas those in the clay-dominated heavy textured soils (i.e., clay loam) showed a wide range (11.3–49.3 kPa). There were large differences in PAWC for dynamic FC (PAWCfc) and fixed FC at 10 kPa (PAWC10), 33 kPa (PAWC33), and a mix of 10 and 33 kPa (PAWC10, 33) pressure heads depending on soil texture. Normally, the difference between PAWC at 10 kPa and hfc (ΔPAWC10) was positive, whereas that between 33 kPa and hfc (ΔPAWC33) was negative across all sites. Nevertheless, the estimation of PAWC assuming a fixed FC at 10 and 33 kPa pressures (i.e., PAWC10, 33) for sandy, clay, and silty soils reduced the difference between fixed and dynamic pressure PAWCs to < 10% across the region. The estimation of PAWC was improved by incorporating the impact of subsoil constraints, such as high ESP, which was more pronounced for clay and silty soils. These findings demonstrate the inherent inconsistencies between static pressure and flux-based dynamic FC estimations in soils. Soil heterogeneity, intra-texture variability, subsoil constraints, and swell-shrink clays can have great impacts on the water retention capacity in response to dynamic and fixed pressure FC values.

The dispersion mechanism of dispersive seasonally frozen soil in western Jilin Province

A large area of soda-saline soil has developed in the seasonally frozen area of western Jilin Province, northeast China. Because of the strong dispersibility of this soil, irrigation channels and other water conservation projects are often damaged or even destroyed by erosion. In this study, grey relational analysis was used to analyze the correlation between the physicochemical properties and dispersibility of the soil and thus reveal the dispersion mechanism. Moreover, the effects of salt migration and microstructural changes on soil dispersion in the seasonally frozen area were studied via a water migration simulation experiment with samples from western Jilin Province. The high cation exchange capacity, high exchangeable sodium percentage, high pH, low organic matter content, and low clay content of the soil were the main factors contributing to soil dispersion. In addition, in winter, salt in the soil constantly moved from the lower non-frozen soil layer to the upper frozen soil layer along with water. After the frozen soil layer thawed in spring, the evaporation of water at the soil surface caused the salt to continuously migrate to the surface along with the water. As a result, the sodium ion content in the surface soil increased considerably thereby enhancing soil dispersibility. However, frost heave increased the distance between soil particles, weakened the structural connection among soil particles, and loosened the soil particles. Therefore, the seasonal freeze-thaw process in the study area promoted soil dispersion. This study has a certain theoretical significance for the construction of water conservancy projects and soil improvement.

Effect of polymaleic acid on saline sodic soils

Saline-sodic soils in Middle Awash Valley area of Ethiopia have very high soluble sodium content and exchangeable sodium percentage (ESP). Leaching soluble salts with water alone could not fasten reclamation of these soils. Because all pore spaces of the soil were already sealed off with precipitated soluble salts; which retarded percolation of leaching water to the soil. Hence, Polymaleic acid was tested under controlled pot leaching under laboratory condition. The treatments were control (leaching with water only), 10, 20, 30 and 40ml polymaleic acid per kilogram of soil. Each treatment was replicated four times. As a result of leaching and polymaleic acid application to the saline - sodic soil, the ECe of the soil was was drastically reduced as the rate of polymaleic acid rate was increased. At the end of leaching, soluble cation and anions were also drastically decreased as compared to the control treatment. Hence, polymaleic acid soil conditioner could be used as an amendment for reclamation of high saline - sodic soils.

SITE-SPECIFIC RECLAMATION MAPS OF A SALT AFFECTED SOIL IN ISMAILIA GOVERNORATE

Delineation of soil management zones is essential for precision agriculture applications, to know agricultural inputs added to soil. Geostatistics provides an effective tool for soil spatial variability and delineating management zones. Spatial variability was done on soil properties to prepare prescription maps for leaching and gypsum requirements (GR) of a salt affected soil. The performance of the spatial model was evaluated by calculating two different statistics. Mean error (ME) as a measure of precision and mean square standardized error (MSSE) as a measure of accuracy were calculated. The developed spatial maps of investigated soil parameters [electrical conductivity (ECe), exchangeable sodium percentage (ESP) and cation exchange capacity (CEC)] were used to specify 4 zones-prescription maps that need leaching and gypsum requirements. Results showed that the three models were precise and accurate with ME and MSSE values (-0.110, -0.210, 0.002 and 0.937, 1.033, 1.010), respectively. Applying site-specific management for leaching proved cost-effective and beneficial effects compared with traditional management which is based on an average value over the experimental field. The (GR) on basis of traditional management was cost-effective but was not more beneficial because zones 1 and 2 showed GR more than needed and vice versa for zones 3 and 4. The high cost in this case could be counterbalanced by the expected increased production in zones with high ESP.

Chemical and physical influence of sodic soils on the coleoptile length and root growth angle of wheat genotypes.

High exchangeable sodium percentage (ESP) and bulk density of sodic soils can reduce seedling emergence. This study examined variation in seedling coleoptile length and seminal root angle of wheat (Triticum aestivum. L) genotypes to determine whether these traits vary between genotypes that differ in their tolerance to sodic soils. Wheat genotypes were grown in three different experiments. First, four wheat genotypes were grown using soils of three ESPs (4, 10 and 17 %) and secondly in soils of three different bulk densities (1.2, 1.4 and 1.5 g cm-3) and ESP 10 %. Thirdly, seedling coleoptile length and seminal root angle were determined for 16 genotypes grown in a soil of ESP 10 % and bulk density 1.2 g cm-2. Seminal root angle and coleoptile length measurements from the current study were compared with seedling emergence rate and force measured previously. The seedling coleoptile length of all genotypes decreased with increasing soil ESP and bulk density, but with no significant differences between genotypes. In contrast, seminal root angles differed significantly between genotypes, but were not significantly affected by ESP or bulk density. There was an inverse relationship between the seminal root angle of the 16 genotypes and seedling emergence rate (R2 = 0.89) and also between seminal root angle and seedling emergence force (R2 = 0.61). Lack of significant variation in coleoptile length between genotypes suggests that this may not be a suitable characteristic to identify wheat tolerance to sodic conditions. However, a narrower seminal root angle was correlated with rate and force of seedling emergence, traits likely to improve establishment. The mechanism underlying this correlation is not yet clear. Genotypes with a narrow root angle had greater root depth. One possible mechanism might be that genotypes with narrow root angles were able to take up more soil moisture at depth, leading to a higher proportion of seedling emergence.

Assessment of Soil Degradation and Large Scale Soil Mapping Using GIS: A Case Study of Village Ramagarh from Purna Valley, Maharashtra

The importance of soil-physiographic relationship in soil survey and mapping provide a fair understanding of variability across the landscape needed for sustainable agricultural planning. Keeping this in view the swell- shrink soils of the Ramagarh village of Purna valley in Amravati district, Maharashtra in semi-arid region of central India were studied for their morphological, physical and chemical characteristics and soils were mapped at 1: 8000 scale in geographical information system (GIS) platform. The soils of Ramagarh village are very deep, dark grayish brown to very dark grayish brown in colour, clayey in texture and exhibits medium, moderate, sub angular blocky structure in the surface layers and the subsoil horizons have medium, weak to strong angular blocky structure. Soils are alkaline in reaction, calcareous in nature and low to medium organic carbon content. The pH, CaCO3 and exchangeable sodium percentage (ESP) increase with depth in all the soils. Because of high smectitic clay content and ESP down the profile, these soils have impeded drainage and show ponding of water in the rainy season. The soils of the uplands are classified as Sodic Haplusterts and low land soils belong to Typic Haplusterts category at sub group level. The study indicates that the soils are sodic chemically degraded in 18.2% area of the TGA of the village. The higher ESP was related to corresponding decrease in exchangeable calcium and increase in exchangeable magnesium.

Characterization and Classification of Soils of Valsad taluka, Valsad District, Gujarat

Five representative pedons (P1 Umarsadi; P2 Segvi; P3 Chikla; P4 Bagal; and P5 Faldhara) from different landforms of Valsad taluka in the coastal region of Valsad district, Gujarat were studied for their morphological, physical, and chemical properties. The soils were deep to very deep, well to imperfectly drained, slightly alkaline to strongly alkaline (pH 7.8 to 9.7), non-saline tosaline (0.1 to 4.4 dS m-1), low to high in organic carbon (2.4 to 12.3 g kg-1) and CaCO3 (0.2 to 19.5%), and medium to high in CEC [21.8 to 69.9 (p+) kg-1]. Soil texture varied from sandy clay loam to clay with clay content ranging from 21.2 to 53.5 %. Bulk density was lower in P5 (1.28-1.33 Mg m-3) than the other pedons (1.21-1.48 Mg m-3). Saturated hydraulic conductivity (sHC) was less than the critical limit of 1.0 cm hr-1 in P3, and generally low due to high (&gt;15) exchangeable sodium percentage (ESP) and exchangeable magnesium percentage (EMP). Pedon P1 was classified as Sodic Haplusterts and P4 as Typic Haplusterts. The pedon P2 with an argillic horizon(&lt;35 cm thickness) in the deeper layerswas classified as Inceptic Haplustalfs. The pedon P3 with lithological discontinuity was classified as Typic Ustifluvents and P5 as Vertic Haplustalfs. The pedons P1, P3 and P4 were developed in the basaltic alluvial parent material, and their subsurface properties were influenced by the paleosols. The pedons P1, P2, and P5 under perennial crops such as mango and eucalyptus have higher organic carbon and lower bulk density. Management measures are required to reduce subsoil sodicity, and sustain crop production in the heavy textured soils.

How Spatial Patterns of Soil Moisture Dynamics Can Explain Field‐Scale Soil Moisture Variability: Observations From a Sodic Landscape

AbstractRoot‐zone soil moisture (0–110 cm) was monitored at 21 sites within a cold‐region semiarid prairie grazing pasture over multiple growing seasons. There were large differences in the moisture dynamics for different sites, which was related to local‐scale impacts of sodium‐induced clay dispersion. Sites with high exchangeable sodium percentages, indicative of sodic soils, were characterized by small changes in soil moisture storage. The sites with the largest soil moisture changes had negligible exchangeable sodium percentage. We used this difference to divide the area into sites that participate in the field‐scale water balance and those that do not. As a result of this heterogeneity, a unique soil moisture variability‐mean relationship was observed; the spatial variability of root‐zone soil moisture was lowest during intermediate wetness conditions and highest for wet and dry conditions. Furthermore, the shape of the variability‐mean relationship depended on the depth over which soil moisture was integrated. The persistent differences in soil moisture dynamics were also responsible for the presence of two distinct spatial patterns of root‐zone soil moisture, representing early and late growing season (i.e., wet and dry conditions). The participating versus nonparticipating framework may be applicable broadly to sodic soils and to other soil types and has practical implications for parameterizing the water balance in hydrological models and for designing representative soil moisture monitoring networks in such environments.

Comparison of methods for evaluating the suitability of Vertisols for Gossypium hirsutum (Bt cotton) in two contrasting agro-ecological regions

ABSTRACTCotton (Gossypium sp.) is a major crop grown under rainfed conditions in Vertisols and associated soils in semi-arid tropical (SAT) regions of Peninsular India. In recent years, cotton productivity has declined due to various biophysical factors including pest and diseases, seasonal water stress soil degradation and poor crop management practices. In this study, we compare two methods for evaluating the suitability of Vertisols for cotton in contrasting two agro-ecological regions viz., sub-humid moist (SHM) region and semi-arid dry(SAD) were characterized. Twelve cotton growing Vertisols (seven from SHM and five from SAD) were evaluated for their suitability for cotton cultivation using soil quality index (SQI) and modified Sys-FAO method. SQIs were calculated using the weighted additive index from transformed scores of selected indicators by principal component analysis. For Sys-FAO method both biophysical and soil characteristics were considered for suitability evaluation. We found that the soils of SHM region were moderately suitable for cotton cultivation with soil moisture as the major limiting factor, whereas the soils of SAD region are marginally suitable due to high exchangeable sodium percentage and poor hydraulic conductivity. From this, it may be concluded that the weighted SQI has better agreement with the cotton yield.

Long-term irrigation with reclaimed wastewater: Implications on nutrient management, soil chemistry and olive (Olea europaea L.) performance

Utilization of reclaimed wastewater (RWW) presents an alternative to irrigation of agricultural crops with fresh water (Fr), especially in dry areas characterized by water scarcity. While RWW often contains considerable amounts of valuable plant nutrients, it is also typically characterized by high salt content, which can impair agricultural yields and have environmental repercussions. The objective of this study was to determine the effect of long-term utilization of RWW and fertilization practice on soil properties and plant performance. We evaluated irrigation and nutrient management of olives with RWW versus Fr in a long-term field experiment. Two olive cultivars (Barnea and Leccino) were subjected to irrigation with RWW, either with standard or reduced fertilization, and irrigation with Fr with standard fertilization.During the eight years of the experiment, considerable amounts of N, P and K were delivered with the RWW. Trees irrigated with RWW receiving no additional fertilization were not negatively impacted, indicating sufficient nutrient allocation by the RWW. Fruit yield was higher in RWW treatments compared to the Fr, probably due to the presence of P. In the autumn of each year, soil salinity was higher in the reclaimed wastewater compared to the fresh water treatment, but this did not lead to increased leaf Na or Cl concentrations or to reduced tree productivity. From an agronomic point of view, the lack of response to salinity implies that irrigation of olive with reclaimed wastewater is sustainable as long as precipitation ensures sufficient seasonal leaching of salts. However, sodium absorption ratio of the soil solution slowly and steadily increased in the reclaimed wastewater treatments resulting in a high exchangeable sodium percentage (14%) reaching nearly double that of the fresh water treatment. The latter observations highlight the likelihood for adverse effects of long-term irrigation with reclaimed wastewater on the deterioration of soil physical and chemical properties.

Identification of indicator species at abandoned red mud dumps in comparison to residential and forest sites, accredited to soil properties

Plant community structure studies on derelict sites are providing significant insights into vegetation dynamics to ensure the success of future revegetation projects in such areas. Therefore, the present study was conducted to evaluate the changes in soil physico-chemical and biological properties at abandoned red mud dumps (RMD) compared to residential (RS) and forest (FS) sites, coupled with their consequent impacts on the plant community structure. An attempt was also made to identify the indicator species that thrive only under unfavourable red mud conditions. Soil at RMD showed relatively high bulk density, alkalinity, salinity and exchangeable sodium percentage along with poor nutrient status and low microbial activity. Though toxic metals (Cd, Cr and Pb) were higher at RMD, their phytoavailabilities were lower compared to FS site. Number of herb-, shrub- and woody species at RMD were although low, but a significant number of species were acclimatized to the unfavourable soil conditions. Shrub species were maximally affected at RMD, followed by woody- and herbaceous species. Important value index of sensitive species was low while that of tolerant species was higher, and was accredited to altered soil properties. Presence of invasive species such as Acacia nilotica, Caesalpinia bonduc, Stylosanthes scabra and Urena lobata at only RMD may be used as an indication for high toxic metal contamination along with high alkalinity, salinity and poor nutrient contents. Principal component and canonical correspondence analyses revealed that woody and herbaceous species were mainly affected by soil alkalinity, salinity, exchangeable cations, bulk density, porosity, moisture content and phytoavailable metals. Shrub species were primarily influenced by soil organic carbon, nitrogen, available phosphorus, bulk density, porosity, moisture content, soil biological parameters, total (Fe, Mg, Cd, Cr and Pb) and phytoavailable metals. Domination of herbaceous species in the plant community indicated their tendency towards a definite selection strategy in response to altered soil properties. The identified tolerant herbaceous species may be suitable candidates for future red mud reclamation strategies.

Impact of brackishwater shrimp farming at the interface of rice growing areas and the prospects for improvement in coastal India

The coastal plain of Odisha in the northeastern region of India is designated the “rice bowl” of the state and is vulnerable to the impact of brackishwater shrimp farming, a prominent livelihood in southeastern Asia. Shrimp farming is highly profitable. However, owing to plentiful resources, shrimp farming has encroached on several rice-growing areas and a decline in the quality of natural resources in the coastal neighborhood has since been reported. This paper aims to study the effects of the unplanned expansion of brackishwater shrimp farming on natural resources and to provide a pathway to suitable utilization in order to improve the livelihood security of marginal shrimp farming communities in coastal Odisha, India. The practice of brackishwater shrimp farming has been determined to induce salt stress at 341–9387 ppt ha−1 crop−1 with a soil EC ranging from 0.3 to 3.4 and 0.5 to 9.5 dSm−1 under the Scientific Extensive Traditional (SET) method and 0.1 to 1.4 and 0.2 to 3.6 dSm−1 under the Traditional/Improved Traditional (IT) practice during post– and pre–farming periods, respectively. Soil with ≥35% clay content underwent a severe loss of saturated hydraulic conductivity (Ks), and soil with a low exchangeable sodium percentage (6.09–8.03%) showed more susceptibility towards Na saturation than did soil with a high exchangeable sodium percentage (>10%) after brackishwater shrimp farming. Growing salt-tolerant rice in shrimp ponds during non–farming periods was observed to reduce soil Ks by only 1.2–1.3-fold compared to a reduction of 22–40-fold under shrimp farming. The paper concludes that by promoting salt washing and alleviating salinity hazards, the shrimp–rice sequence has shown promise to restore soil quality, reduce vulnerability, enhance resilience in brackishwater shrimp farming where the farms interface with rice-growing coastal areas, and provide support to conserve the coastal environment.

Soil biological properties and carbon dynamics subsequent to organic amendments addition in sodic black soils

ABSTRACTThe field experiments on calcareous sodic Vertisols were conducted on farmer’s fields in Purna valley of Vidarbha region of Maharashtra. The treatments comprised of different green manures (GMs); crop residues (CRs); gypsum. The chemical and biological properties after 2 years experiment showed that the application of gypsum recorded significant drop in pH and exchangeable sodium percentage (ESP) as compared to organic amendments. But later has outperformed with respect to biological activities viz., dehydrogenase activity (DHA) and microbial respiration and carbon sequestration by enhancing soil organic carbon (SOC), soil organic carbon (SOC) stock, soil microbial biomass carbon (SMBC) and labile carbon pool (POXC). Among the different organic amendments the application of dhaincha improved SMBC by 90%, microbial respiration by 104%, POXC by 59% and DHA by 265% as compare to control. High ESP of these soils showed negative relationship with microbial respiration and POXC (r = 0.48 and r = 0.43, p = < 0.05). While addition of biomass showed positive relationship with SMBC, microbial respiration, POXC and DHA (r = 0.93, r = 0.81, r = 0.83 and r = 0.91 p = < 0.01). The results of study showed green manuring in sodic black soil found to be alternative choice to gypsum, which besides gradual reclamation also enhance biological properties and carbon sequestration.

Genetic Diversity in Barley and Wheat for Tolerance to Soil Constraints

Surface soil sodicity as well as subsoil salinity, acidity, and phytotoxic concentrations of chloride (Cl) are major soil constraints to crop production in many soils of sub-tropical, north-eastern Australia. The identification of genotypes tolerant to these soil constraints may be an option to maintain and improve productivity on these soils. We evaluated performance of 11 barley and 17 wheat genotypes grown on two sites &lt;0.5 km apart. Compared to the non-sodic site, the sodic site had significantly higher Cl concentration (&gt;800 mg·Cl·kg−1) in the subsoil (0.9–1.3 m soil depth) and higher exchangeable sodium percentage (ESP) (&gt;6%) in the surface and subsoil. Barley grain yield and plant available water capacity (PAWC) were reduced between 5%–25% and 40%–66%, respectively, for different genotypes at the sodic site as compared to the non-sodic site. For wheat genotypes, grain yield was between 8% and 33% lower at the sodic site compared to the non-sodic site and PAWC was between 3% and 37% lower. Most barley and wheat genotypes grown at the sodic site showed calcium (Ca) deficiency symptoms on younger leaves. Analysis of the youngest fully mature leaf (YML) confirmed that genotypes grown at the sodic site with Ca concentration &lt; 0.2% exhibited deficiency symptoms. Grain yields of both barley and wheat genotypes grown on the sodic and non-sodic sites increased significantly with increasing Ca and K in YML and decreased significantly with increasing Na and Cl concentrations in YML. Sodium (Na) concentrations in YML of wheat genotypes grown at the sodic site were 10-fold higher than those from the non-sodic site whereas this increase was only two-fold in barley genotypes. In step-wise regression, the PAWC of barley and wheat genotypes grown on sodic and non-sodic sites was the principal determinant of variability of barley and wheat grain yield. Including the Ca concentration in the YML of wheat genotypes and K:Na ratio in the YML of barley genotypes significantly improved the prediction of grain yield in the regression analysis. Barley genotypes, Mackay and Kaputar, were relatively susceptible while Baronesse and Grout were relatively more tolerant to sodicity. Wheat genotypes Gregory and Stampede were generally relatively more susceptible to sodicity, and genotypes Baxter, Hume, and the experimental line HSF1-255 were relatively more tolerant than the former group.

Evaluation of Salt Affected Soils for Rice (Oryza Sativa) Production in Ndungu Irrigation Scheme Same District, Tanzania

A study was carried out to examine distribution of salt affected soils by types and extent in the Ndungu Agricultural Development Project (NADP) area of Tanzania. The objective was to generate information to guide salt-affected soil management for sustainable rice production. Conventional methods including use of mini-pits and profile pits, coupled with farmers’ experiences were used to characterise soil. A total of seven randomly selected soil profile pits located in major soils were dug and described. Soil was sampled from natural horizons for laboratory analysis. In addition a total of 158 topsoil (0 – 20 cm depth) composites soil samples were randomly collected from 90 sites of NADP project area for laboratory analysis. Results showed that a few blocks (block is a piece of farm of 6 to 12 acres) had high exchangeable sodium percentage and high levels of bicarbonates, indicating salt-affected soils. Soil pH, exchangeable sodium percentage (ESP), and electrical conductivity of soil paste extract (ECe) values as high as 9.06, 28.7 cmol(+)Nakg-1, and 14dSm-1 were measured. Out of 90 blocks, 10 blocks (11%) showed slight to strong salt effects. Two blocks (2%) has been abandoned, and in some cultivated blocks zero yields were recorded due to salt content. The different levels of salinity development in the project area suggest site-specific remediation and appropriate management options be developed to improve crop production. These include rehabilitation of the irrigation infrastructure, use of farmyard manure as a soil amendment and growing salt-tolerant rice varieties. Furthermore, it is important to create awareness among farmers of the problem of salt-affected soil on rice productivity.

Physical and chemical degradation of grassland soils in semi-arid regions: A case from Central Anatolia, Turkey

The aim of this study is to determine some hydro-physical and chemical characteristics of soils on the grassland areas under semi-arid conditions in terms of soil degradation processes. Three sampling plots of 20 × 20 m size were selected from the Emen Plain as Locations-I, II and III basing on the area covered with vegetation and visual soil properties; and total 108 soil samples from 2 points and 3 depth levels (0–20 cm, 20–40 cm, 40–60 cm) of each sampling plot. Soils of the research area are in degradation process in terms of some physical and chemical characteristics. It was observed that soil properties (i.e. bulk density, total porosity, organic matter, pH, electrical conductivity and saturated hydraulic conductivity) in Location-II and Location-III changed negatively in comparison to Location-I almost at all depths. In the Location-III grassland, bulk density, pH, electrical conductivity and Na + values are higher than those in Location-I, whereas the organic matter, total porosity and saturated hydraulic conductivity values are low. Grassland area is vulnerable to erosion. High Exchangeable Sodium Percentage (ESP) values in Locations-II and III indicates the sodicity problem in these areas.

Effect of gypsum on exchangeable sodium percentage and electrical conductivity in the Daeho reclaimed tidal land soil in Korea—a field scale study

A reclaimed tidal land along the shore has poor soil properties such as high exchangeable sodium percentage (ESP), and electrical conductivity (EC) due to excess sodium (Na) content. Therefore, Na content should be decreased to improve the land productivity, and for this, gypsum has been widely used. The objective of this study was to determine the changes in ESP and EC of the gypsum-treated reclaimed tidal soil in a field scale. For this, gypsum was applied to Daeho reclaimed tidal land (500 ha) in Korea for 5 years (2006 to 2010). The Daeho reclaimed tidal land has been used as reclaimed paddy fields since 1993. The application rate of gypsum was calculated based on exchangeable calcium (Ca) contents and soil cation exchange capacity (CEC) to maintain 60 % exchangeable calcium percentage (ECP) of CEC in soil and the average amount treated was 1570 kg ha−1 year−1. The changes in ESP and EC were monitored from 2006 to 2010, and 2013. The ESP dropped from 80 % in 2006 to 34 % in 2013. The EC of the soil was decreased by 73 %, from 11.5 dS m−1 in 2006 to 3.1 dS m−1 in 2013. Eventually, it was estimated that the ESP will be lowered below 15 % in 2023 with continuous treatment of gypsum according to ECP calculation, and EC will be declined to reach at 0.5 dS m−1 in 2035, the average EC level of Korean rice paddy. This field scale study evidenced that gypsum application effectively improves the soil properties of reclaimed tidal soil by decreasing ESP and EC.

The abundance of functional genes, cbbL, nifH, amoA and apsA, and bacterial community structure of intertidal soil from Arabian Sea

The Gulf of Cambay is a trumpet-shaped inlet of the Arabian Sea, located along the west coast of India and confronts a high tidal range with strong water currents. The region belongs to a semi-arid zone and saline alkaline intertidal soils are considered biologically extreme. The selected four soil types (S1–S4) were affected by salinity, alkalinity and sodicity. Soil salinity ranged from 20 to 126dS/m, soil pH 8.6–10.0 with high sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP). Abundance of the key functional genes like cbbL, nifH, amoA and apsA involved in biogeochemical cycling were targeted using qPCR, which varied from (2.36±0.03)×104 to (2.87±0.26)×108, (1.18±0.28)×106 to (1.01±0.26)×109, (1.41±0.21)×106 to (1.29±0.05)×108 and (8.47±0.23)×104 to (1.73±0.01)×106 per gram dry weight, respectively. The microbial community structure revealed that soils S1 and S3 were dominated by phylum Firmicutes whereas S4 and S2 showed an abundance of Proteobacterial clones. These soils also represented Bacteroidetes, Chloroflexi, Actinobacteria, Planctomycetes and Acidobacteria clones. Molecular phylogeny showed a significant variation in the bacterial community distribution among the intertidal soil types. A high number of novel taxonomic units were observed which makes the intertidal zone a unique reservoir of unidentified bacterial taxa that may be explored further.