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1.
Abstract

Growth response of Matricaria chamomilla, L. was investigated on a range of soil salinity and sodicity levels using fine and coarse‐textured soil types. Twenty treatments including 4 levels of salinity and 4 levels of sodicity on each soil type were examined in addition to control. On the coarse‐textured soils, chamomile responded best under relatively low saline and sodic conditions. Plant growth decreased with increase in salinity and sodicity. On the fine‐textured soils, plants endured saline conditions up to 13 ECe and grew better under sodic conditions. The best growth of plants was achieved on fine‐textured soils with sodicity level of 31.8 Esp.  相似文献   

2.
Osmotic potential (OP) of soil solution may be a more appropriate parameter than electrical conductivity (EC) to evaluate the effect of salts on plant growth and soil biomass.However,this has not been examined in detail with respect to microbial activity and dissolved organic matter in soils with different texture.This study evaluated the effect of salinity and sodicity on respiration and dissolved organic matter dynamics in salt-affected soils with different texture.Four non-saline and non-sodic soils differing in texture (S-4,S-13,S-24 and S-40 with 4％,13％,24％ and 40％ clay,respectively) were leached using combinations of 1 mol L-1 NaC1 and 1 mol L-1 CaC12 stock solutions,resulting in EC (1:5 soil:water ratio) between 0.4 and 5.0 dS m-1 with two levels of sodicity (sodium absorption ratio (SAR) ＜ 3 (non-sodic) and 20 (sodic),1:5 soil:water ratio).Adjusting the water content to levels optimal for microbial activity,which differed among the soils,resulted in four ranges of OP in all the soils:from-0.06 to--0.24 (controls,without salt added),-0.55 to-0.92,-1.25 to-1.62 and-2.77 to-3.00 Mpa.Finely ground mature wheat straw (20 g kg-1) was added to stimulate microbial activity.At a given EC,cumulative soil respiration was lower in the lighter-textured soils (S-4 and S-13) than in the heavier-textured soils (S-24 and S-40).Cumulative soil respiration decreased with decreasing OP to a similar extent in all the soils,with a greater decrease on Day 40 than on Day 10.Cumulative soil respiration was greater at SAR =20 than at SAR ＜ 3 only at the OP levels between-0.62 and-1.62 MPa on Day 40.In all the soils and at both sampling times,concentrations of dissolved organic C and N were higher at the lowest OP levels (from-2.74 to-3.0 MPa) than in the controls (from-0.06 to-0.24 MPa).Thus,OP is a better parameter than EC to evaluate the effect of salinity on dissolved organic matter and microbial activity in different textured soils.  相似文献   

3.
Salt accumulation has a negative effect on microorganisms, but plant residues may enhance the microbial activity and biomass. An experiment was conducted over 50 days to evaluate the effect of wheat and alfalfa residues on microbial activity and biomass and nitrogen (N) and phosphorus (P) availability in sandy and clayey soils at different salinity levels. Equivalent amounts of calcium (Ca+2) and sodium (Na+) salts were added to both soils. Values of electrical conductivity (EC1:5), denoted S1, S2, and S3 in each soil, were 0.16, 1.10 and 1.98 dS m?1 in the sand and 0.19, 0.82 and 1.75 dS m?1 in the clay. Residues of wheat and alfalfa were added at 2% (w/w). Cumulative respiration and microbial biomass decreased with increasing salinity, but with residue addition they increased with a greater rate in amended sandy soil than in clay soil, with a more pronounced effect for alfalfa than for wheat residue. After 10 days, with wheat residue available N values were 113, 86, and 71 μg in the clay and 144, 114, and 94 μg g?1 soil in the sand in S1, S2, and S3, respectively. Relative to wheat residue, alfalfa residue increased N availability by 9, 13, and 19% and 22, 24, and 24% in the clay and in the sand in S1, S2, and S3, respectively. Compared to the control, in the clay P availability increased by 33, 57, and 100% with wheat residue and by 58, 128, and 175% with alfalfa residue, whereas in the sand it increased by 92, 45, and 40% with wheat residue and by 130, 145, and 280% with alfalfa residue in S1, S2, and S3, respectively. Availability of N and P increased from day 10 to day 50 in both soils, but with different magnitudes. Residue addition can increase microbial activity and nutrient availability in saline soils, particularly in coarser textured soils.  相似文献   

4.
In salt-affected soils, soil organic carbon (SOC) levels are usually low as a result of poor plant growth; additionally, decomposition of soil organic matter (SOM) may be negatively affected. Soil organic carbon models, such as the Rothamsted Carbon Model (RothC), that are used to estimate carbon dioxide (CO2) emission and SOC stocks at various spatial scales, do not consider the effect of salinity on CO2 emissions and may therefore over-estimate CO2 release from saline soils. Two laboratory incubation experiments were conducted to assess the effect of soil texture on the response of CO2 release to salinity, and to calculate a rate modifier for salinity to be introduced into the RothC model. The soils used were a sandy loam (18.7% clay) and a sandy clay loam (22.5% clay) in one experiment and a loamy sand (6.3% clay) and a clay (42% clay) in another experiment. The water content was adjusted to 75%, 55%, 50% and 45% water holding capacity (WHC) for the loamy sand, sandy loam, sandy clay loam and the clay, respectively to ensure optimal soil moisture for decomposition. Sodium chloride (NaCl) was used to develop a range of salinities: electrical conductivity of the 1:5 soil: water extract (EC1:5) 1, 2, 3, 4 and 5 dS m−1. The soils were amended with 2% (w/w) wheat residues and CO2 emission was measured over 4 months. Carbon dioxide release was also measured from five salt-affected soils from the field for model evaluation. In all soils, cumulative CO2-C g−1 soil significantly decreased with increasing EC1:5 developed by addition of NaCl, but the relative decrease differed among the soils. In the salt-amended soils, the reduction in normalised cumulative respiration (in percentage for the control) at EC1:5 > 1.0 dS m−1 was most pronounced in the loamy sand. This is due to the differential water content of the soils, at the same EC1:5; the salt concentration in the soil solution is higher in the coarser textured soils than in fine textured soils because in the former soils, the water content for optimal decomposition is lower. When salinity was expressed as osmotic potential, the decrease in normalised cumulative respiration with increasing salinity was less than with EC1:5. The osmotic potential of the soil solution is a more appropriate parameter for estimating the salinity effect on microbial activity than the electrical conductivity (EC) because osmotic potential, unlike EC, takes account into salt concentration in the soil solution as a function of the water content. The decrease in particulate organic carbon (POC) was smaller in soils with low osmotic potential whereas total organic carbon, humus-C and charcoal-C did not change over time, and were not significantly affected by salinity. The modelling of cumulative respiration data using a two compartment model showed that the decomposition of labile carbon (C) pool is more sensitive to salinity than that of the slow C pool. The evaluation of RothC, modified to include the decomposition rate modifier for salinity developed from the salt-amended soils, against saline soils from the field, suggested that salinity had a greater effect on cumulative respiration in the salt-amended soils. The results of this study show (i) salinity needs to be taken into account when modelling CO2 release and SOC turnover in salt-affected soils, and (ii) a decomposition rate modifier developed from salt-amended soils may overestimate the effect of salinity on CO2 release.  相似文献   

5.
In the Far West Texas region in the USA, long‐term irrigation of fine‐textured valley soils with saline Rio Grande River water has led to soil salinity and sodicity problems. Soil salinity [measured by saturated paste electrical conductivity (ECe)] and sodicity [measured by sodium adsorption ratio (SAR)] in the irrigated areas have resulted in poor growing conditions, reduced crop yields, and declining farm profitability. Understanding the spatial distribution of ECe and SAR within the affected areas is necessary for developing management practices. Conventional methods of assessing ECe and SAR distribution at a high spatial resolution are expensive and time consuming. This study evaluated the accuracy of electromagnetic induction (EMI), which measures apparent electrical conductivity (ECa), to delineate ECe and SAR distribution in two cotton fields located in the Hudspeth and El Paso Counties of Texas, USA. Calibration equations for converting ECa into ECe and SAR were derived using the multiple linear regression (MLR) model included in the ECe Sampling Assessment and Prediction program package developed by the US Salinity Laboratory. Correlations between ECa and soil variables (clay content, ECe, SAR) were highly significant (p ≤ 0·05). This was further confirmed by significant (p ≤ 0·05) MLRs used for estimating ECe and SAR. The ECe and SAR determined by ECa closely matched the measured ECe and SAR values of the study site soils, which ranged from 0·47 to 9·87 dS m−1 and 2·27 to 27·4 mmol1/2 L−1/2, respectively. High R2 values between estimated and measured soil ECe and SAR values validated the MLR model results. Results of this study indicated that the EMI method can be used for rapid and accurate delineation of salinity and sodicity distribution within the affected area. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

6.
Saline–sodic and sodic soils are characterized by the occurrence of sodium (Na+) to levels that can adversely affect several soil properties and growth of most crops. As a potential substitute of cost‐intensive chemical amelioration, phytoremediation of such soils has emerged as an efficient and low‐cost strategy. This plant‐assisted amelioration involves cultivation of certain plant species that can withstand ambient soil salinity and sodicity levels. It relies on enhanced dissolution of native calcite within the root zone to provide adequate Ca2+ for the Na+ Ca2+ exchange at the cation exchange sites. There is a lack of information for the Na+ balance in terms of removal from saline–sodic soils through plant uptake and leaching during the phytoremediation process. We carried out a lysimeter experiment on a calcareous saline–sodic soil [pH of saturated soil paste (pHs) = 7.2, electrical conductivity of the saturated paste extract (ECe) = 4.9 dS m−1, sodium adsorption ratio (SAR) = 15.9, CaCO3 = 50 g kg−1]. There were three treatments: (1) control (without application of a chemical amendment or crop cultivation), (2) soil application of gypsum according to the gypsum requirement of the soil and (3) planting of alfalfa (Medicago sativa L.) as a phytoremediation crop. The efficiency of treatments for soluble salt and Na+ removal from the soil was in the order: gypsum ≈ alfalfa > control. In the phytoremediation treatment, the amount of Na+ removed from the soil through leaching was found to be the principal cause of reduction in salinity and sodicity. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

7.
Historically many towns in inland Australia disposed of their treated sewage by pumping into local rivers. This is no longer a feasible proposition. Alternatives to river pumping include irrigation and/or aquaculture. As treated sewage effluent may contain large amounts of nitrogen, phosphorus and sodium salts, if not managed carefully, soil salinity, sodicity and nutrient accumulation could increase. The objective of this study was to evaluate if gypsum application had any effect on soil‐quality changes in a Vertisol due to irrigating a cotton–wheat rotation with tertiary treated sewage effluent. The treatments were application of 2·5 t ha−1 of gypsum in June 2000 before commencing irrigation and an untreated control. Annually, between June 2000 and April 2004, irrigation water quality and soil changes in nitrate‐N, EC1:5, pH, organic carbon, Cl, dispersion index, and exchangeable cations to a depth of 1·8 m were measured and deep drainage inferred with the chloride mass balance method. Cotton lint yield and fibre characteristics were also evaluated. Irrigation with treated sewage effluent increased exchangeable Na in all depths, and exchangeable Ca and K in the clayey‐textured surface 0·6 m, but decreased exchangeable Ca and K, and SOC in the coarser clay‐loam‐textured depths > 0·6 m. Nitrate‐N leaching, associated with deep drainage had occurred, as the crops had not used all the N in irrigation water. Gypsum application decreased exchangeable Ca, increased dispersion and during the 2003–2004 season deep drainage, but had no effect on salinity, sodicity or pH. Application of commercial gypsum at sub‐optimal rates with sodium‐rich irrigation water is, therefore, unlikely to improve soil properties. Stubble incorporation before sowing cotton in 2003 appears to have mobilized gypsum applied during 2000. Gypsum application reduced cotton lint yield and fibre quality during 2003–2004. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

8.
The individual effects of salinity and sodicity on organic matter dynamics are well known but less is known about their interactive effects. We conducted a laboratory incubation experiment to assess soil respiration and dissolved organic matter (DOM) dynamics in response to salinity and sodicity in two soils of different texture. Two non-saline non-sodic soils (a sand and a sandy clay loam) were leached 3–4 times with solutions containing different concentrations of NaCl and CaCl2 to reach almost identical electrical conductivity (EC1:5) in both soils (EC1:5 0.5, 1.3, 2.5 and 4.0 dS m?1 in the sand and EC1:5 0.7, 1.4, 2.5 and 4.0 dS m?1 in the sandy clay loam) combined with two sodium absorption ratios: SAR < 3 and 20. Finely ground wheat straw residue was added (20 g kg?1) as substrate to stimulate microbial activity. Cumulative respiration was more strongly affected by EC than by SAR. It decreased by 8% at EC 1.3 and by 60% at EC 4.0 in the sand, whereas EC had no effect on respiration in the sandy clay loam. The apparent differential sensitivity to EC in the two soils can be explained by their different water content and therefore, different osmotic potential at the same EC. At almost similar osmotic potential: ?2.92 MPa in sand (at EC 1.3) and ?2.76 MPa in the sandy clay loam (at EC 4.0) the relative decrease in respiration was similar (8–9%). Sodicity had little effect on cumulative respiration in the soils, but DOC, DON and specific ultra-violet absorbance (SUVA) were significantly higher at SAR 20 than at SAR < 3 in combination with low EC in both soils (EC 0.5 in the sand and EC 0.7 and 1.4 in the sandy clay loam). Therefore, high SAR in combination with low EC is likely to increase the risk of DOC and DON leaching in the salt-affected soils, which may lead to further soil degradation.  相似文献   

9.
The effects of zeolite application (0, 4, 8 and16 g kg?1) and saline water (0.5, 1.5, 3.0 and 5.0 dS m?1) on saturated hydraulic conductivity (K s) and sorptivity (S) in different soils were evaluated under laboratory conditions. Results showed that K s was increased at salinity levels of 0.5‐1.5 dS m?1 in clay loam and loam with 8 and 4 g zeolite kg?1 soil, respectively, and at salinity levels of 3.0–5.0 dS m?1 with 16 g zeolite kg?1 soil. K s was decreased by using low and high salinity levels in sandy loam with application of 8 and 16 g zeolite kg?1, respectively. In clay loam, salinity levels of 0.5–3.0 dS m?1 with application of 16 g kg?1 zeolite and 5.0 dS m?1 with application of 8 g zeolite kg?1 soil resulted in the lowest values of S. In loam, all salinity levels with application of 16 g zeolite kg?1 soil increased S compared with other zeolite application rates. In sandy loam, only a salinity level of 0.5 dS m?1 with application of 4 g zeolite kg?1 soil increased S. Other zeolite applications decreased S, whereas increasing the zeolite application to 16 g kg?1 soil resulted in the lowest value of S.  相似文献   

10.
Development of alternative sources through wastewater reuse is important to meet water demands in arid regions. However, effects of wastewater irrigation on soil properties and crop performance must be evaluated before advocating its widespread use. Objectives of this study were to evaluate: (i) effects of prior evaporative disposal of saline‐sodic blowdown water (BW) on soil (fine‐loamy, mixed, and thermic Typic Calciorthods) properties in the disposal area, and (ii) effects of flood irrigation with three water qualities (control, BW 1X, and BW 2X) on soil salinity and alfalfa performance using a greenhouse soil column study (soil collected from same study area as objective (i)). Results indicated that although prior land disposal of BW had increased salinity and sodicity of soil, they were within the tolerance limits of the intended crop, alfalfa. Mass balance calculations indicated measured (15·6 Mg ha−1) and calculated (13·2 Mg ha−1) salt accumulation at the test site used for evaporative disposal were similar. Alfalfa grown using BW under greenhouse conditions produced prime quality hay and biomass yield similar to the control treatment (8·3 g column−1 vs. 10·5 g column−1 in control). Although 3·6 years equivalent of flood irrigation with BW 1X did not result in saline soil (BW 1X irrigated soils EC ranged from 2·2 to 3·5 dS m−1), BW 2X irrigation resulted in saline soils. Sodicities of irrigated soils were greater in fine textured deep soils than coarse textured surface soils (e.g., SAR of 6·1 at 0–5 cm vs. 19·5 mmol1/2 L−1/2 at 30–60 cm in BW 1X), indicating the need for high solubility Ca amendments for long‐term irrigation with BW on fine texture soils within the soil profile. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

11.
Excess of exchangeable sodium (Na) in salt-affected soils causes ion toxicity and decrease in nutrient uptake by plants, particularly potassium (K). A number of studies have been conducted to investigate the effect of K-fertilization on plant growth under sodic and saline-sodic conditions but the results are much diverse to process for concrete recommendations. To explore the possible reasons, it was hypothesized that Na applied as NaCl to produce salinity/sodicity in the soil may release non-exchangeable K, minimizing the effect of K-fertilization. Incubation studies were conducted for 2, 4 and 6 days in the light (sandy loam) and heavy (clay loam) textured soils producing two saline/sodic levels, i.e. 20 and 30 sodium adsorption ratio (SAR) along with control (SAR 3). Potassium fertilizer applied was calculated according to 40 (general recommendations based on soil-nutrient status), 80 and 160 kg K ha?1. Interestingly, it was observed that addition of NaCl possibly released non-exchangeable K from the soil minerals and increased the K concentration in soil solution. Total K release was more in heavy textured soil but initial release was more in light textured soil. This release may eliminate the effect of K-fertilization applied under salt stress induced by NaCl. Therefore, it is suggested that while studying Na–K interaction in salt-affected soils, NaCl should be avoided to produce salinity, and naturally occurring saline-sodic soils may be used. Soil Na–K interaction studies including ameliorating effect of K under sodic or saline-sodic conditions should be conducted carefully considering the above-stated argument.  相似文献   

12.
The effect of total electrolyte concentration (TEC) and sodium adsorption ratio (SAR) of water on ESR‐SAR relationships of clay (Typic Haplustert), clay loam (Vertic Haplustept) and silt loam (Lithic Haplorthent) soils was studied in a laboratory experiment. Twenty four solutions, encompassing four TEC levels viz., 5, 10, 20, and 50 mmolc l—1 and six SAR levels viz., 2.5, 5, 10, 15, 20, and 30 mmol1/2l—1/2 were synthesized to equilibrate the soil samples using pure chloride salts of calcium, magnesium, and sodium at Mg:Ca = 1:2. SAR of equilibrium solution decreased as compared to the equilibrating solution and more so in waters of low salt concentration and high SAR. At low electrolyte concentration, high SAR values were not attained in the equilibrium solution because of addition of calcium and magnesium from the mineral dissolution and from the exchange phase. Irrespective of TEC, exchangeable sodium in all the soils increased by about 4.5 to 5‐fold and irrespective of SAR, it increased by about 1.4‐ to 1.8‐fold. A positive interaction of TEC and SAR influenced the ESP build‐up and CEC played a major role in the visual disparity in sodication of these soils. At higher TEC levels, considerable increase in ESP was observed when it was corrected for anion exclusion and more so in silt loam followed by clay loam and clay soils. The values for Gapons' constant were in the range 0.0110—0.0176, 0.0142—0.0246, and 0.0189—0.0344 mmol—1/2l1/2 in clay, clay loam, and silt loam soils, respectively. Increase in TEC from 5 to 50 mmolc l—1 resulted in 5.84, 8.33, and 9.77 % decrease in Gapons' constant of clay, clay loam, and silt loam soils, respectively. The soils exhibited differential affinity for Ca2+, Mg2+ or Na+ under different quality waters. Regression coefficients of ESR‐SAR relationship were lower for low TEC as compared with high TEC waters. The exchange equilibrium was strongly affected by TEC of the solution phase. Variation in soil pH was gradual with respect to TEC and SAR of equilibrating solution and no sharp change was observed. Soluble salt concentration was doubled upon equilibration with low salt waters at all SAR levels in all the soils. However, the salt concentration remained unchanged upon equilibration with high salt waters. Considering pH 8.5 a boundary between soil salinity and sodicity, ESP values attained at TEC 5 mmolc l—1 were 7.34, 8.02, and 14.32 for clay, clay loam, and silt loam soils, respectively.  相似文献   

13.
Saline‐sodic water is a by‐product of coalbed natural gas (CBNG) production in the Powder River Basin of Wyoming, USA and is being beneficially used in places as irrigation water. This study evaluated effects of 2 years of natural precipitation on soil properties of a hay field after the cessation of managed irrigation with CBNG water. The hay field had been irrigated with only CBNG water [CBNG(NT)], CBNG water amended with gypsum [CBNG(G)] or gypsum plus sulfur via a sulfur burner [CBNG(GSB)] in combination with soil amendments—gypsum ( +G ), elemental sulfur ( +S ), and both ( +GS ). Results indicated that infiltration rates were the lowest on fields irrigated with CBNG(NT), followed by CBNG(G) and CBNG(NT) +G treatments (12·2, 13·2, and 13·5 cm h−1, respectively). The CBNG(GSB) +GS treatment had the highest infiltration rates (33·5 cm h−1). By the second year, salinity and sodicity of treated soils had decreased in the A‐horizon of most CBNG‐water irrigated plots, whereas in Bt1‐ and Bt2‐horizons salinity generally decreased but sodicity increased; S and GS soil amended plots had higher profile salinities compared with NT and G soil treatments. Although Na+ leaching was observed in all fields that received soil and/or water amendments, CBNG(GSB) +GS plots had the lowest sodicity in the A‐ and Bt1‐horizons. Effective managed irrigation requires knowledge of site‐specific soil properties, plant suitability, water chemistry, and amendments that would be needed to treat the CBNG waters and soils. This study indicates the greatest success was realized when using both soil and water amendments. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

14.
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15.
Abstract: In recent years, sulfur (S) deficiencies in winter wheat (Triticum aestivum L.) have become more common, particularly on coarse‐textured soils. In Study I, field experiments were conducted in 2001/2002 through 2003/2004 on Mississippi River alluvial soils (Experiment I) and an upland, loessial silt loam (Experiment II) to evaluate the influence of spring S rates of 0, 5.6, 11.2, and 22.4 kg ha?1 and a fall rate of 22.4 kg sulfate (SO4)‐S ha?1 on grain yield of three varieties. In Study II, field experiments were conducted in 2001/2002 and 2004/2005 on alluvial soils to evaluate the influence of spring S rates of 0, 5.6, 11.2, and 22.4 kg SO4‐S ha?1 in fields where S‐deficiency symptoms were present. Grain yield response to applied S occurred only on alluvial, coarse‐textured, very fine sandy loam soils (Study II) that had soil SO4‐S levels less than the critical level of 8 mg kg?1 and organic‐matter contents less than 1 g kg?1 in the 0‐ to 15‐, 15‐ to 30‐, and 30‐ to 45‐cm depths. Soil pH increased with soil depth. Optimum S rate was 11.2 kg SO4‐S ha?1 in 2001/2002 and 5.6 kg SO4‐S ha?1 in 2004/2005. On the upland, loessial silt loam soil, soil SO4‐S levels accumulated with depth, whereas organic‐matter content and pH decreased. In the loessial soils, average soil SO4‐S levels in the 15‐ to 30‐ and 30‐ to 45‐cm soil depths were 370% greater than SO4‐S in the surface horizon (0 to 15 cm).  相似文献   

16.
Understanding soil water dynamics and storage is important to avoid crop failure on highly weathered, porous and leached soils. The aim of the study was to relate soil moisture characteristics to particle-size distributions and chemical properties. On average, Atterberg limits were below 25% in the A-horizon and not more than26.56% in the B-horizon, whereas soil bulk density was between 1.27 and 1.66Mgm?3. The saturated hydraulic conductivity (Ksat) was generally between 0.20 and 5.43 cm h?1 in the top soil and <1.31 cm h?1 in the subsoil. The higher Ksat values for the A-horizons were attributed to the influence soil microorganisms operating more in that horizon. The amount of water retained at field capacity or at permanent wilting point was greater in the B-horizons than in the A-horizons, suggesting that clay accumulation in the B-horizon and evapotranspiration effects in the A-horizon may have influenced water retention in the soils. Soil moisture parameters were positively related to clay content, silt content, exchangeable Mg2+, Fe2O3 and Al2O3, and negatively related to sand content, SiO2, sodium absorption ratio, exchangeable sodium percentage and bulk density. The low clay content may explain why drainage was so rapid in the soils.  相似文献   

17.
The large genotypic variation for salt tolerance in rice and wheat is the driving force behind efforts to identify appropriate cultivars for salt‐prone environments where large variations in salinity (electrical conductivity, EC) and sodicity (sodium adsorption ratio, SAR) levels exist. An evaluation of the commonly grown rice and wheat cultivars at different EC/SAR ratios may thus help in coping with the crop failures on salt‐affected soils. Accordingly, we evaluated some salt‐tolerant cultivars of rice and wheat for growth and yield at different soil salinity and sodicity levels in a sandy clay loam soil. Among the cultivars tested, rice ‘SSRI‐8’ produced the highest productive tillers and paddy yield, and wheat cultivar ‘SIS‐32’ produced the highest tillers and grain and straw yields. The high EC/SAR ratios proved more hazardous for rice than for wheat. Irrespective of the varieties tested, the highest levels of EC and SAR (T5 and T6) caused significant reduction in paddy yield, whereas at the lowest levels of EC and SAR (T1 and T2), paddy yield was not affected significantly when compared with the control. However, in case of wheat crop, all the levels [i.e., the lowest (T1 and T2), medium (T3 and T4), and the highest (T5 and T6) of EC and SAR tested] affected wheat yield adversely with significant differences. For both the crops, there were little or no differences in yield between the two ratios tested (i.e., 1:2 and 1:4) at all the levels of EC and SAR.  相似文献   

18.
盐化和有机质对土壤结构稳定性及阿特伯格极限的影响   总被引：14，自引：1，他引：14  
对甘肃景电灌区盐化和有机质对土壤团聚体的稳定性、黏粒的分散性及阿特伯格极限进行了调查研究。研究结果表明该灌区盐化土壤中水溶性盐以钠盐为主,土壤具有钠质现象。随含盐量和交换性钠离子百分率（ESP）的增加土壤团聚体的稳定性显著降低,黏粒的分散性显著增加,阿特伯格极限具有降低的趋势,明确地说明盐化和伴随着的钠质化是土壤结构性能退化的主要原因。随有机质含量的增加,土壤团聚体的稳定性显著增加,黏粒的分散性显著降低,阿特伯格极限显著增加,说明增加有机质含量可以显著改善盐化土壤的结构性能。可以根据如下公式利用有机质含量（OM）和ESP预测团聚体的稳定性:WSAR=19.4 0.98OM-1.43 ESP（R2=0.5741,n=67）。团聚体稳定性、黏粒分散性、流限和塑限互相之间显著相关,说明流限和塑限可以作为反映盐化土壤结构状况的指标。  相似文献   

19.
Abstract

Electrical conductivity (EC) methods were tested using combinations of surrogate irrigation (SI) waters, soil salinity levels, and soils ground or retaining aggregates. The EC varied in low-salinity soils saturated with SI; the sum of the baseline ECe and SI EC were not equal to the measured EC. The baseline ECe and the SI EC sum in the high‐salinity ground soils were not equal to the any measured ECs. Salt‐removal potential from gypsiferous soils was examined using multiple extractions from the same soil sample. Calcium concentrations remained consistent over 14 extractions, whereas Na concentrations decreased. The ECe decreased from more than 8 dS m?1 in the initial extraction, to approximately 4 dS m?1 by the 9th to 14th extraction. Multiple extraction data suggest that improved leaching will not lower soil ECs to less than approximately 4 dS m?1 because of gypsum and calcite reservoirs in the tested soils.  相似文献   

20.
The aim of this study was to determine the effects of plant absence or presence on microbial properties and enzyme activities at different levels of salinity in a sandy clay soil. The treatments involved five salinity levels—0.5 (control), 2.5, 5, 7.5, and 10 dS m?1 which were prepared using a mixture of chloride salts—and three soil environments (unplanted soil, and soils planted with either wheat or clover) under greenhouse conditions. Each treatment was replicated three times. At the end of the experiment, soil microbial respiration, substrate-induced respiration (SIR), microbial biomass C (MBC), and enzyme activities were determined after plant harvest. Increasing salinity decreased soil microbial properties and enzyme activities, but increased the metabolic quotient (qCO2) in both unplanted and planted soils. Most microbial properties of planted soils were greater than those of unplanted soils at low to moderate salinity levels, depending upon plant species. There was a small or no difference in soil properties between the unplanted and planted treatments at the highest salinity level, indicating that the indirect effects of plant presence might be less important due to significant reduction of plant growth. The lowered microbial activity and biomass, and enzyme activities were due to the reduction of root activity and biomass in salinized soils. The lower values of qCO2 in planted than unplanted soils support the positive influence of plant root and its exudates on soil microbial activity and biomass in saline soils. Nonetheless, the role of plants in alleviating salinity influence on soil microbial activities decreases at high salinity levels and depends on plant type. In conclusion, cultivation and growing plant in abandoned saline environments with moderate salinity would improve soil microbial properties and functions by reducing salinity effect, in particular planting moderately tolerant crops. This helps to maintain or increase the fertility and quality of abandoned saline soils in arid regions.  相似文献   

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