Fabrication of electrospun meta-aramid nanofibers in different solvent systems

Meta-aramid fibers were dissolved in four different solvent systems (DMAc, DMF, NMP, and DMSO) and two kinds of salts (LiCl and CaCl₂) were also introduced in this paper. Meta-aramid fibers had a limited solubility in above four solvents, however, fast dissolution could be obtained after adding a certain amount of salt (LiCl or CaCl₂). The concentration of salts was found to be an important role in affecting meltaging, dissolving time and viscosity of electrospun solution. Electrospun meta-aramid nanofibers mats were successfully prepared. A series of characterizations had been carried out by using SEM. The results shows the diameter of meta-aramid nanofibers ranging from 100 to 500 nm. The average diameter of the nanofibers increased with the concentration of meta-aramid fiber solution and the salt solution. A preferable morphology of meta-aramid nanofibers could be obtained under LiCl/DMAc system. While the electrospun nanofibers made in CaCl₂/DMAc solvent system had a better performance in thermal stability than that prepared in LiCl/DMAc system. Among the four kinds of prepared nanofibers, the nanofibersmat electrospun in LiCl/DMAc system with a concentration of meta-aramid solution at 11 wt% exhibit the best mechanical properties.     

Growth and Saxitoxin Production by Cylindrospermopsis raciborskii (Cyanobacteria) Correlate with Water Hardness

The cosmopolitan and increasing distribution of Cylindrospermopsis raciborskii can be attributed to its ecophysiological plasticity and tolerance to changing environmental factors in water bodies. In reservoirs in the semi-arid region of Brazil, the presence and common dominance of C. raciborskii have been described in waters that are considered hard. We investigated the response of a Brazilian C. raciborskii strain to water hardness by evaluating its growth and saxitoxin production. Based on environmental data, a concentration of 5 mM of different carbonate salts was tested. These conditions affected growth either positively (MgCO₃) or negatively (CaCO₃ and Na₂CO₃). As a control for the addition of cations, MgCl₂, CaCl₂ and NaCl were tested at 5 or 10 mM, and MgCl₂ stimulated growth, NaCl slowed but sustained growth, and CaCl₂ inhibited growth. Most of the tested treatments increased the saxitoxin (STX) cell quota after six days of exposure. After 12 days, STX production returned to concentrations similar to that of the control, indicating an adaptation to the altered water conditions. In the short term, cell exposure to most of the tested conditions favored STX production over neoSTX production. These results support the noted plasticity of C. raciborskii and highlight its potential to thrive in hard waters. Additionally, the observed relationship between saxitoxin production and water ion concentrations characteristic of the natural environments can be important for understanding toxin content variation in other harmful algae that produce STX.     

Enhanced physico-mechanical properties of polyester resin film using CaCO<Subscript>3</Subscript> filler

Bio-based CaCO₃ powder was synthesized via size reduction method from waste eggshells. The XRD analysis revealed that eggshell powder consists of CaCO₃ in calcite form. The inclusion level of CaCO₃ contents were varied of 5, 10, 15, 20 and 25 wt.% of prepared CaCO₃-polyester film. Effects of different proportions of prepared chicken eggshell and commercial CaCO₃ filler on the polyester resin composites films were compared by means of mechanical and physical test. It was found that the addition of CaCO₃ filler to the polyester films leads to improve the mechanical properties. The findings revealed that the best and optimum CaCO₃ filler content was 10 wt.% and among the prepared polyester films, eggshell CaCO₃-polyester films showed the best performance. The mechanical properties of CaCO₃-polyester films were measured in terms of tensile strength, elongation-at-break, tensile modulus, flexural strength and impact strength. For eggshell CaCO₃- polyester films, the maximum values of the aforementioned mechanical properties were 52.70 MPa, 4.63 %, 1868.70 MPa, 101.20 MPa and 8.40 kJ/m², respectively, whereas for commercial CaCO₃-polyester films those values were 48.12 MPa, 4.50 %, 1790.30 MPa, 97.50 MPa and 8.21 kJ/m², respectively. Further, water absorption of the composite films as a function of time had also been investigated at 10 wt.% filler content.     

The synergy effect of Graphene/SiO<Subscript>2</Subscript> hybrid materials on reinforcing and toughening epoxy resin

Based on the situ preparation of silica nanoparticles (SiO₂) on the surface of Graphene nanoplatelets (GNPs) in the previous work, these unique three dimensional (3D) materials were introduced into epoxy resin to study the reinforcing and toughening synergy effect on the composites. Firstly, the tensile tests showed that Graphene/SiO₂ hybrid materials attached with different size of SiO₂ particles exhibited different reinforcing and toughening effect on the composites. With the increasing of the diameter of SiO₂ particles, the toughness and strength properties of the composites firstly improved and then decreased, and when the average diameter was 0.14 μm, the elongation reached the max.. Meanwhile, the fractured surfaces presented on SEM images were consistent with the results of the tensile tests, which further explained the hybrid materials increased the interfacial adhesion between the fillers and matrix, leading to significant improvement in mechanical properties. Moreover, the DSC curves demonstrated that Graphene/SiO₂ hybrid materials accelerated the curing process of epoxy resin due to the cross-link structure between fillers and matrix. Lastly, the crack propagation modes were built to clarify the synergy effect mechanism of reinforcing and toughening on nanoparticles/epoxy resin composites.     

Nano-SiO2in-situ hybrid polyurethane leather coating with enhanced breathability

A novel in-situ nano hybrid technique combined with industrialized wet phase inversion coating-forming process was developed for the modification of polyurethane (PU) leather coating with nano-SiO₂. During the wet phase inversion process, nano-SiO₂ particles were in-situ generated synchronously as polyurethane resin coagulated. Scanning electron microscope analysis indicated that when the SiO₂ concentration was limited within 1.5 wt%, the size scale of in-situ generated nano-SiO₂ ranged from 70 to 150 nm, which were well-separated and dispersed uniformly throughout the PU coating. After nano hybridization, extra mesopores were detected in the PU coating by nitrogen adsorption/desorption experiment. These mesopores were correlated with enhanced water vapor and gas (hydrogen, nitrogen, and oxygen) permeability, which could improve the breathability or wear comfort of PU leather. In spite of extra mesopores, the hybrid PU coating maintained comparable hydrostatic pressure to control. Nevertheless, when the SiO₂ concentration was increased up to more than 1.5 wt%, micro-SiO₂ particles and agglomerates dominated throughout the PU coating, which obstructed mass transportation and lowered the breathability of the coating. Without disturbing established wet phase inversion coating-forming process in PU leather industry, the novel in-situ nano hybrid technique developed in this study may be of great potential for producing PU leather with improved breathability on an industrial scale.     

Influence of synergism caused by organic montmorillonite and nanometer calcium carbonate on mechanical properties and crystallization of polyamide 1010-based composites

This account showed that nanometer-active calcium carbonate (CaCO₃) improved polyamide 1010/organic montmorillonite (OMMT) composites and OMMT boosted polyamide 1010/CaCO₃. The mechanical performance suggested the composites to be reinforced through adsorption forces present between the nanofillers and the matrix. The synergistic effect of CaCO₃ and OMMT increased the yields and shrunk cavities when observed by scanning electron microscopy. The obvious resulting synergism was verified by X-ray scattering techniques after the addition of OMMT. The concentration of CaCO₃ did not change lamellar-size or influence the crystal growth. The effect of CaCO₃ on melting behavior was found less significant than that exert on crystallization behavior.     

低温胁迫下外源CaCl2对玉米种子萌发及幼苗生长的影响

以杂C-546为试材,采用10、20、40、80、160 mmol/L外源CaCl_2浸种和叶面喷施不同浓度处理种子,比较分析低温胁迫下玉米种子发芽率、发芽势、发芽指数和幼苗叶片相对电导率、可溶性蛋白、Pn、Fv/Fm、POD和SOD活性等生理生化指标的变化。结果表明,在低温抑制玉米幼苗生长条件下,一定浓度CaCl_2(10~80 mmol/L)处理可降低玉米幼苗生长伤害程度。80 mmol/L CaCl_2浸种处理对玉米低温胁迫的缓解效果最佳,与对照比较,发芽率提高8%,发芽势提高24.6%,发芽指数提高33.2,相对电导率降低51.8%,可溶性蛋白含量增加76.3%,SOD活性增加35.7%。适宜浓度的CaCl_2在低温条件下可促进玉米种子的萌发,降低低温对玉米幼苗造成的伤害。     

Homogeneous self-cleaning coatings on cellulose materials derived from TIP/TiO2 P25

The aim of this research was to study TiO₂ nanocoatings formation and to investigate their self-cleaning effects when applied on cellulose materials. Two different approaches for achieving nanocoatings were used. First, coatings were generated in situ through an acid and alkaline catalyzed sol-gel process with or without added water. Another type of coatings was prepared starting from commercial TiO₂ P25 powder. In order to acquire homogeneous coatings from TiO₂ P25 nanoparticles with uniform nanoparticles size distribution, pH of aqueous TiO₂ P25 dispersions was varied. The dispersion preparation conditions were studied by dynamic light scattering (DLS) and zeta potential (ζ-potential) analysis. The resulting TiO₂ nanocoatings were analyzed in terms of their surface morphology using scanning electron microscopy (SEM). Nanocoatings obtained from pure aqueous dispersions of TiO₂ P25 nanoparticles were inhomogeneous with huge agglomerates; however by changing the pH of dispersion and consequently changing the surface charge of TiO₂ P25 nanoparticles as well, more homogeneous nanocoatings with uniform TiO₂ nanoparticles distribution were prepared. Significant differences between solgel derived coatings were observed. Sol-gel process without added water yielded more homogeneous coatings than sol-gel process with addition of water. Completely different surface morphologies were obtained using alkaline or acid catalyst. Acid catalyzed sol-gel process yielded nanocoatings with long, extended, thin structures; contrary, under alkaline conditions particles grow in size with decrease in number. Fourier transform infrared (FTIR) spectroscopy was used to study the coatings’ microstructure. Furthermore the formation of mono-disperse nanoparticles on the fiber surface resulted in enhanced photocatalytic activity. Degradation of colored stain applied on TiO₂-treated samples was investigated by colorimetric measurements. Photocatalytic activity of nanocoatings prepared via acid catalyzed sol-gel process without water addition was comparable to that of nanocoatings derived from aqueous dispersions of commercial TiO₂ P25 nanoparticles.     

Effect of calcium carbonate nanoparticles on barrier properties and biodegradability of polylactic acid

In this study, the effect of calcium carbonate (CaCO₃) nanoparticles on the barrier properties and biodegradability of polylactic acid (PLA) was investigated. For this purpose, nanocomposite films with various CaCO₃ nanoparticle contents (0, 3, 5, 10, and 15 wt%) were prepared by solution casting method. The gas permeability of nitrogen (N₂), oxygen (O₂), and carbon dioxide (CO₂) was evaluated through a constant volume and variable pressure apparatus at different pressures and temperatures. According to results, barrier properties were improved by loading CaCO₃ nanoparticles up to 5 wt%, and the gas permeability of CO₂, O₂, and N₂ was decreased from 1.4, 0.31, and 0.07 Barrer to 0.48, 0.095, and 0.019 Barrer, respectively. In addition, it was also observed that the gas permeability of samples was decreased by increasing feeding pressure and increased by enhancing temperature. Furthermore, morphological results confirmed the formation of agglomerations and large clusters over 5 wt% CaCO₃ nanoparticles. Finally, the thermal properties and biodegradability of PLA were increased by employing CaCO₃ nanoparticles. These results suggested PLA nanocomposites as favorable candidates for food packaging applications.     

Thermal and mechanical properties of modified CaCO3 filled poly (ethylene terephthalate) nanocomposites

Poly(ethylene terephthalate) (PET)/CaCO₃ and PET/modified-CaCO₃ (m-CaCO₃) nanocomposites were prepared by melt blending. The morphology indicated that m-CaCO₃ produced by reacting sodium oxalate and calcium chloride, was well dispersed in PET matrix and showed good interfacial interaction with PET compared to CaCO₃. No significant differences in the thermal properties such as, glass transition, melting and degradation temperatures, of the nanocomposites were observed. The thermal shrinkage of PET at 120 °C was 10.8 %, while those of PET/CaCO₃ and PET/m-CaCO₃ nanocomposites were 2.9–5.2 % and 1.2–2.8 %, respectively depending on filler content. The tensile strength of PET/CaCO₃ nanocomposite decreased with CaCO₃ loading, whereas that of PET/m-CaCO₃ nanocomposites at 0.5 wt% loading showed a 17 % improvement as compared to neat PET. The storage modulus at 120 °C increased from 1660 MPa for PET to 2350 MPa for PET/CaCO₃ nanocomposite at 3 wt% loading, and 3230 MPa for PET/m-CaCO₃ nanocomposite at 1 wt% loading.     

Manufacture of non-resin wheat straw fibreboards

Wheat straw was used as raw material in the production of fibreboards. The size-reduced straw was pretreated with steam, hot water and sulphuric acid before the defibration process to loosen its physical structure and reduce the pH. No synthetic binder was added. Adhesive bonding between fibres was initiated by activation of the fibre surfaces by an oxidative treatment during the defibration process. Fenton’s reagent (ferrous chloride and hydrogen peroxide) was added. Two different levels of hydrogen peroxide (H₂O₂), 2.5% or 4.0% were used. The resulting fibres were characterized in terms of fibre length distribution, shive content, pH and pH-buffering capacity. The properties of finished fibreboards were compared with medium-density fibreboard (MDF) with density above 800 kg/m³ produced from straw and melamine modified UF resin. The modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB) were lower than those of conventional manufactured wheat straw fibreboards but close to the requirements of the MDF standard (EN 622-5: 2006). The water absorption properties for the H₂O₂ activated straw fibreboards were relatively high, but were reduced by 25% with the addition of CaCl₂ into the defibrator system as a water-repelling agent. Increased levels of hydrogen peroxide improved the mechanical and physical properties of the straw fibreboard.     

Performance of PTT fabric treated with CNTs/SiO<Subscript>2</Subscript>/thiazole dye hybrid materials

A series of CNTs/SiO₂/thiazole dye hybrid materials prepared via the sol-gel process is synthesized from carbon nanotubes (CNTs) and tetraethoxysilane with heteroaryl 4-phenyl-2-amino-thiazole dyes. Heterocyclic 4-phenyl-2-aminothiazole dyes are processed with the hydrolysis-condensation reaction at a constant ratio of vinyltriethoxysilane and tetraethoxysilane condensed with modified CNTs in appropriate proportion under a catalyst. The structures of the CNTs/SiO₂/thiazole dye hybrid materials are characterized by Fourier transform infrared spectroscopy (FTIR). Polytrimethylene terephthalate (PTT) fabrics are used to evaluate the morphology structure by scanning electron microscopy (SEM). SEM images show that a uniform dyeing on the PTT fabrics to confirm the reaction of hybrid materials with PTT fabrics. The washing fastness, color evenness, water contact angle, air permeability, electric conductivity, and weatherability of PTT fabrics dyed with CNTs/SiO₂/thiazole dye hybrid materials are evaluated, with results indicating improved conductivity and water-repellent.     

Fabrication of PVA-BaSO4 hybrid nanofibers and dispersion of BaSO4 particles via ultrasonic electrospinning

We reported the preparation and characterization of the poly(vinyl alcohol) (PVA)/BaSO₄ hybrid nanofibers prepared by normal and ultrasonic electrospinning, respectively. Compared to normal electrospinning, BaSO₄ particles in the resultant PVA/BaSO₄ hybrid nanofibers prepared by ultrasonic electrospinning were well-dispersed without severe agglomerations, as confirmed by scanning electron microscopy (SEM) analysis. X-ray diffraction (XRD) analysis indicated that typical crystalline peaks of PVA and BaSO₄ particles were dramatically decreased by ultrasonication during electrospinning. Moreover, the size of BaSO₄ aggregates became smaller.     

Structure and performance of<Emphasis Type="Italic">Bombyx mori</Emphasis> silk modified with nano-TiO<Subscript>2</Subscript> and chitosan

Bombyx mori (B. mori) silk was modified with the nano-TiO₂ and chitosan dispersion system by the crosslinking reactions of citric acid (CA) and maleic anhydride (MA). The average size of the nano-TiO₂ particles in the aqueous dispersion system was 36.7 nm. The scanning electron microscopy (SEM) micrographs showed that the nano-TiO₂ particles were spherical and homogeneously dispersed in the dispersion system, and the surface ofB. mori silk fiber treated with the nano-TiO₂ and chitosan dispersion system was rougher than that of the untreated one. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) Spectrometry indicated that the crystallinity of theB. mori silk fiber increased after treatment. It was also found that the nano-TiO₂ and chitosan contributed to significantly enhance the mechanical properties including breaking strength, breaking elongation, initial modulus, rupture work, and elastic recovery property of theB. mori silk fiber. The wrinkle-resistant performance of the treatedB. mori silk fabrics was also greatly improved.     

Synthesis,structure and thermal protective behavior of silica aerogel/PET nonwoven fiber composite

In recent years, flexible, mechanically strong and environmental friendly thermal insulation materials have attracted considerable attention. In this work, silica aerogel/polyethylene terephthalate (PET) nonwoven fiber composite with desirable characteristics was prepared via a two-step sol-gel process followed by an ambient drying method through immersing the PET nonwoven fiber into silica sol. The silica aerogel particles were characterized by FTIR, FE-SEM, TGA and nitrogen adsorption analysis. The morphology and hydrophobic properties of neat PET nonwoven fiber and its silica aerogel composite were also investigated. For studying thermal protective properties, the thermal diffusivity was calculated from temperature distribution curves. The mean pore size of 11 nm, the surface area of 606 m²/g and the total pore volume of 1.77 cm³/g for the silica aerogel particles in the composite are obtained from nitrogen adsorption analysis, indicating the aerogel can maintain its high porosity in the nonwoven composite structure. Silica aerogel particles were efficiently covered the surface of the PET fibers and completely filled the micron size pores of the nonwoven fiber leading to a stronger hydrophobicity and higher thermal insulation performance in the aerogel composite samples compared to the neat PET nonwoven. In this regard, an almost 64 % decrease in the thermal diffusivity was achieved with 66 wt% silica aerogel.     

Effects of various chemical blanchings on the texture of French fries

Trial blanching with CaCl₂, MgCl₂ and Ca-citrate improved the texture of low specific gravity fries. For overall textural improvement, CaCl₂ was considered most effective. Best results were obtained by blanching for 15 minutes at 158 F in 0.5% calcium chloride salt solution.     

Wood-wool cement board using mixture of eucalypt and poplar

This study was carried out to explore the possibility of making cement-bonded wood-wool composite building products using eucalypt (Eucalyptus camaldulensis) and poplar (Populus deltoides). The experimental design consisted of three treatments - ratio of wood-wool mixture, percentage concentration of cement, and calcium chloride (CaCl₂). The mechanical properties in terms of modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB) strength were investigated. The ratios of wood-wool to cement were 40:60 and 60:40 by weight. The addition of the woody material to cement clearly reduced the maximum hydration temperature and increased the time to maximum temperature. Eucalypt was generally less compatible with cement than poplar wood. Test results showed that boards made with poplar wood-wools had superior properties compared to the eucalypt and mixed wood-wools. The presence of eucalypt in mixture of woody materials typically resulted in decrease in mechanical properties. It has been noted that a dose of 5% of CaCl₂ by weight of cement can enhance the effect of cement. Application of Duncan's Multiple Range Test for the mean values of the results showed that the effects of all variables and their interactions on the mechanical properties in terms of MOR, MOE and IB were highly significant (p ≤ 0.01%). The mechanical properties of most produced boards were found to satisfy the minimum requirements of ISO standard.     

Sound absorption properties of spiral vane electrospun PVA/nano particle nanofiber membrane and non-woven composite material

In this research, we fabricated a series of PVA membranes loaded with 0 wt.%, 1 wt.%, 3 wt.%, 5 wt.% ZrC and 0 wt.%, 1 wt.%, 3 wt.%, 5 wt.% TiO₂ using a spiral vane electrospun machine respectively. There were 2 sizes of TiO₂ nano particles: 10 nm and 200 nm. We tested sound absorption properties of needle-punched nonwovens as well as the composite of nano membranes and needle-punched nonwovens by an impedance tube at the frequency range from 500 Hz to 6500 Hz. Besides, we tested morphological characterization of nano membranes by scanning electron microscope (SEM) and crystalline properties by X-ray diffraction (XRD). We investigated the sound absorption properties of composites as well as the effect of ZrC, TiO₂, nano particle sizes and cavity depth on sound absorption properties. Results showed that sound absorption properties of composites increased at the whole range of frequency compared to those of needle-punched nonwovens. When loaded with ZrC nano particles, sound absorption properties of composite shifted to a higher frequency region, and with increasing content of ZrC, sound absorption properties were better above 2500 Hz. However, when loaded with TiO₂, sound absorption properties were better at lower frequency. With 3 wt.% TiO₂, sound absorption coefficient reached the best at the frequency range from 500 Hz to 1500 Hz. Besides, 200 nm TiO₂ was more conductive to the increase of sound absorption properties at lower frequency region compared to 10 nm TiO₂. Sound absorption properties of composites with air back cavity shifted to a lower frequency region, too. SEM showed that there was nano particle aggregation when loaded TiO₂ nano particles. XRD showed that ZrC nano particles loaded in PVA nano fiber retained their crystalline structure while TiO₂ didn’t. It appeared from the results that nano particles had an effect on sound absorption materials, with different kinds and different sizes, sound absorption properties will improve in different ranges of frequency     

Si-Al hybrid effect of waterborne polyurethane hybrid sizing agent for carbon fiber/PA6 composites

The interface of fiber-reinforced composites has remained a vexing problem that limits the use of the excellent properties of carbon fiber (CF) in composite applications. In the present study, waterborne polyurethane (WPU) hybrid sizing agents were prepared to improve the performances of CFs and the interface strength of CF/PA6 composites. The structural and mechanical properties of the single-CF and CF/PA6 composites were systematic investigated. The results showed that the mechanical properties of the CF/PA6 composites were significantly improved by adding of WPU hybrid sizing agent. The tensile and flexural strengths of the WPU/SiO₂/Al₂O₃ hybrid sizing agent treated CF/PA6 composites were increased by 24.0 % and 25.7 % than those of no-sizing treated CF/PA6 composites, respectively.     

Effects of long-term use of sodic water irrigation, amendments and crop residues on soil properties and crop yields in rice-wheat cropping system in a calcareous soil

One of the options to ameliorate the deleterious effects of sodic water irrigation is to apply gypsum to soil. We examined whether the application of organic manures or crop residue can reduce the need for gypsum in calcareous soils. A long-term field experiment with annual rice-wheat cropping rotation was conducted for 15 years (1991-2006) on a non-saline calcareous sandy loam soil (Typic Ustochrept) in northwestern, India. The irrigation water treatments included good quality canal water (CW) and sodic water (SW) with residual sodium carbonate (RSC) of 10 mmol_c L⁻¹ from 1991 to 1999 and of 12.5 mmol_c L⁻¹ from 2000 onwards. Gypsum was applied at 0, 12.5, 25, and 50% of the gypsum requirement (GR), to neutralize RSC of the SW. Three organic material treatments consisted of application of farmyard manure (FYM) at 20 Mg ha⁻¹, Sesbania green manure (GM) at 20 Mg ha⁻¹, and wheat straw (WS) at 6 Mg ha⁻¹. The organic materials were applied every year to the rice crop. Continuous irrigation with sodic water for 15 years without gypsum or organic materials resulted in a gradual increase in soil pH and exchangeable sodium percentage (ESP), deterioration of soil physical properties, and decrease in yields of both rice and wheat. The cumulative yield loss in SW irrigated plots without gypsum and organic materials remained <1.5 Mg ha⁻¹ for up to eight years in the case of rice and up to nine years in the case of wheat. Thereafter, marked increase in pH and ESP resulted in further depression in yields of rice by 1.6 Mg ha⁻¹ year⁻¹ and wheat by 1.2 Mg ha⁻¹ year⁻¹. Application of gypsum improved physical and chemical properties of the soil. The beneficial effects on crop yields were visible up to 12.5% GR in rice and up to 50% GR in wheat in most of the years. All the organic materials proved effective in mobilizing Ca²⁺ from inherent and precipitated CaCO₃ resulting in decline in soil pH and ESP, increase in infiltration rate, and a increase in the yields of rice and wheat crops. Although the application of organic materials resulted in comparable reductions in pH and ESP, the increase in yield with SW was higher for both crops with FYM. Pooled over the last six years (2000-2006), application of FYM resulted in 38 and 26% increase in rice and wheat yields, respectively, over SW treatment; corresponding increases in 50% GR treatment (recommended level) was 18 and 19%. During these years, application of GM and WS increased wheat yields by 20%; for rice, GM resulted in 22% increase compared to 17% in WS amended SW irrigated plots. Combined application of gypsum and organic materials did not increase the yields further particularly in the case of FYM and GM treated plots. This long-term study proves that organic materials alone can be used to solubilize Ca from inherent and precipitated CaCO₃ in calcareous soils for achieving sustainable yields in sodic water irrigated rice-wheat grown in annual rotation. The results can help reduce the dependency on gypsum in sodic water irrigated calcareous soils.