Field-specific nutrient management using Rice Crop Manager decision support tool in Odisha, India.

The requirement of rice (Oryza sativa L.) for fertilizer can depend on crop and soil management practices, which can vary among fields within a rice-growing area. A web-based decision support tool named Rice Crop Manager (RCM) was developed previously to calculate field-specific rates of fertilizer N, P, and K for rice in Odisha State in eastern India. We compared field-specific nutrient management calculated by RCM with farmers' fertilizer practice (FFP) and a blanket fertilizer recommendation (BFR), which used a uniform 80 kg N ha-1, 17 kg P ha-1, and 33 kg K ha-1. A total of 209 field trials were conducted in two seasons (kharif and rabi) for two years across ten districts in six agro-climatic zones. Grain yield was consistently higher with fertilization recommended by RCM than with FFP. Higher yield with RCM was attributed to a combination of applying more of the total fertilizer N at the critical growth stage of panicle initiation, applying more fertilizer N in kharif, and applying zinc. The RCM recommendation frequently increased yield compared to BFR as a result of improved N management, which included the adjustment of N rate for a target yield set slightly higher than historical yield reported by a farmer. Fertilization based on RCM rather than BFR reduced the risk of financial loss. The effectiveness of an RCM recommendation relative to BFR and FFP was consistent across rice varieties with different growth duration, irrigated and rainfed rice, and three categories of soil clay content. The RCM recommendation failed to increase yield relative to BFR in one of the six agro-climatic zones, where a higher rate of fertilizer P and/or K was apparently required. The nutrient management calculations used by RCM can be improved as new information and research findings become available. Experiences with RCM in Odisha can help guide the development of comparable nutrient management decision tools in other rice-growing areas.

Structural and Magnetic Properties of Dilute Ca²âº Doped Iron Oxide Nanoparticles.

Undoped and calcium substituted hematite (α-Fe2O3) nanoparticles are synthesized by surfactant-directed co-precipitation and post annealing method. The annealed nanoparticles were found to be in single phase in nature and crystallize in the rhombohedral structure with space group R3c as confirmed by Rietveld refinement of the X-ray diffraction (XRD) data. Average crystallite sizes are calculated to be 20 to 30 nm and 50 to 60 nm for the nanoparticles annealed at 400 and 600 °C respectively. Mössbauer spectra for all the nanoparticles could be fitted with a sextet corresponding to the single magnetic state of the iron atoms in its Fe³âº state in the hematite matrix. The FTIR and Raman spectra of all the samples correspond to specific modes of α-Fe2O3. UV-Vis spectra of annealed samples showed broad peaks in the range of 525-630 nm resulting from spin-forbidden ligand field transition together with the spin-flip transition among the 2t2g states. The estimated band gap energies were in the range of 1.6 to 1.9 eV which are much lower than the reported values for nano hematite. From the room temperature magnetic hysteresis loop measurements, weak ferromagnetic behavior is observed in all undoped and Ca²âº doped hematite samples. Morin temperature (T(M)) is calculated to be 257 and 237 K for 1.45% doped samples with particle size 54 and 27 nm respectively. The sample with Ca content of 1.45 wt% when annealed at 400 °C showed that the particles were of different shapes which included both quasi spherical and rod shaped. On annealing the same sample at 600 °C, the nanorods collapsed to form bigger spherical and ellipsoidal particles.

2-line ferrihydrite: synthesis, characterization and its adsorption behaviour for removal of Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions.

Nano-structured 2-line ferrihydrite was synthesized by a pH-controlled precipitation technique at 90 °C. Chemical, X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman analyses confirmed the sample to be 2-line ferrihydrite. The nano nature of the prepared sample was studied by transmission electron microscopy (TEM). The surface area obtained by the Brunauer-Emmett-Teller (BET) method was 175.8 m(2) g(-1). The nanopowder so obtained was used to study its behaviour for the removal of Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions. The relative importance of experimental parameters such as solution pH, contact time and concentration of adsorbate on the uptake of various cations was evaluated. By increasing the pH from 2.0 to 5.5, adsorption of the four cations increased. The kinetics parameters were compared by fitting the contact time data to both linear as well as non-linear forms of pseudo-second-order models. Linear forms of both Langmuir and Freundlich models fitted the equilibrium data of all the cations except for Pb(II) which was also fitted to the non-linear forms of both the models as it gave a low R(2) value of 0.85 for the Langmuir model. High Langmuir monolayer capacities of 366, 250, 62.5 and 500 mg g(-1) were obtained for Pb(II), Cd(II), Cu(II) and Zn(II), respectively. Presence of chloride or sulfate had an adverse effect on cation adsorption. The interactive effects on adsorption from solutions containing two, three or four cations were studied. Surprisingly no Cd(II) adsorption was observed in Pb(II)-Cd(II), Pb(II)-Cd(II)-Zn(II) and Pb(II)-Cd(II)-Cu(II)-Zn(II) systems under the studied concentration range. The overall loading capacity of the adsorbent decreased in mixed cation systems. Metal ion loaded adsorbents were characterized by XRD, FTIR and Raman techniques. The high adsorption capability of the 2-lines ferrihydrite makes it a potentially attractive adsorbent for the removal of cations from aqueous solutions.

Fluoride adsorption studies on mixed-phase nano iron oxides prepared by surfactant mediation-precipitation technique.

Mixed nano iron oxides powder containing goethite (α-FeOOH), hematite (α-Fe(2)O(3)) and ferrihydrite (Fe(5)HO(8)·4H(2)O) was synthesized through surfactant mediation-precipitation route using cetyltrimethyl ammonium bromide (CTAB). The X-ray diffraction, FTIR, TEM, Mössbauer spectroscopy were employed to characterize the sample. These studies confirmed the nano powder contained 77% goethite, 9% hematite and 14% ferrihydrite. Fluoride adsorption onto the synthesized sample was investigated using batch adsorption method. The experimental parameters chosen for adsorption studies were: pH (3.0-10.0), temperature (35-55°C), concentrations of adsorbent (0.5-3.0 g/L), adsorbate (10-100 mg/L) and some anions. Adsorption of fluoride onto mixed iron oxide was initially very fast followed by a slow adsorption phase. By varying the initial pH in the range of 3.0-10.0, maximum adsorption was observed at a pH of 5.75. Presence of either SO(4)(2-) or Cl(-) adversely affected the adsorption of fluoride in the order of SO(4)(2-)>Cl(-). The FTIR studies of fluoride loaded adsorbent showed that partly the adsorption on the surface took place at surface hydroxyl sites. Mössbauer studies indicated that the overall absorption had gone down after fluoride adsorption that implies it has reduced the crystalline bond strength. The relative absorption area of ferrihydrite was marginally increased from 14 to 17%.

Synthesis of Mg(II) doped goethite and its cation sorption behaviour.

Modified goethite samples were prepared with Mg(II) content varying in the range of 0-1.36%. A typical TEM of Mg(II) doped sample showed needle shaped goethite particles having 10-30 nm width and 100-400 nm length. Sorption studies of cations namely Pb(II), Cu(II), Cd(II), Zn(II) and Fe(III) were conducted onto the Mg(II) doped modified goethite surface. Goethite doping with 0.18 M Mg (GMg(2)) showed better sorption capacity for Pb(II), Cu(II) and Cd(II). Therefore, the effect of contact time, solution pH, sorbate and sorbent concentrations on the sorption of various metal ions was studied on this sample in batch experiments. The time data fitted to pseudo-second-order kinetics for all the metal ions. Sorption on GMg(2) sample for the metal ions increased with the increase in pH from 2 to 4. The isothermic data showed good fit to both Langmuir and Freundlich isotherms except for Cd(II) which followed only the later model. The sorption capacities with respect to Pb(II), Cd(II), Zn(II), Cu(II) and Fe(III) were found to be 87.7, 153.25, 86.25, 33.4 and 72.5mg/g respectively. The results of sorption studies on GMg(2) from binary and ternary solutions have also been presented. The XRD patterns of metal ion loaded GMg(2) samples confirmed that metal ion adsorption resulted in shifting of d-values/altering of relative intensity (RI) of major planes of goethite.

Sorption behavior of Pb(II) and Cd(II) on iron ore slime and characterization of metal ion loaded sorbent.

The present investigation evaluates the sorption effectiveness of Pb(II) and Cd(II) ions on iron ore slime (IOS) obtained from Jindal Steel Ltd., Vijayanagaram, India. The sorption followed pseudo-second-order kinetics for both the cations. Pb(II) and Cd(II) sorption increased with the increase in pH from 2 to 4.5. The sorption data fitted well to Freundlich model as compared to Langmuir model. Synergistic effect of Pb(II) and Cd(II) on their sorption on IOS sample showed that Pb(II) sorption increases in presence of Cd(II) whereas Cd(II) sorption decreases. Presence of chloride or sulphate resulted in increased Pb(II) sorption but adversely affected Cd(II) sorption. The XRD patterns of Pb(II) adsorbed on IOS sample showed disappearance of some silica peaks and shifting of hematite peaks corresponding to 104 and 110 plane. For Cd(II) sorbed IOS sample, only peak shift for hematite of 104 and 110 plane was observed. Shifting of IR bands indicated that the Pb(II) sorption occurred through an inner sphere mechanism where as Cd(II) sorption occurred through outer sphere mechanism. EPMA studies showed that Pb(II) form a uniform thin layer and Cd(II) concentrate only on iron oxide phase. Regeneration and stability data on metal ion loaded IOS sample has been included.