Lessons from upstream soil conservation measures to mitigate soil erosion and its impact on upstream and downstream users of the Nile River

A study was conducted to evaluate the effects of soil bunds stabilized with vetiver grass (V. zizanioides) and tree lucerne (C. palmensis) on selected soil physical and chemical properties, bund height, inter-terrace slope and barley (Hordeum vulgare L.) yield in Absela site, Banja Shikudad District, Awi administrative Zone of the Amhara National Regional State (ANRS) located in the Blue Nile Basin. The experiment had five treatments that included non-conserved land (control), a 9-year old soil bund stabilized with tree lucerne, a 9-year old soil bund stabilized with vetiver grass, a 9-year old sole soil bund, and a 6-year old soil bund stabilized with tree lucerne. Data were analyzed using one-way analysis of variance (ANOVA) and mean values for the treatments were separated using the Duncan Multiple Range Test. Results of the experiment indicated that organic carbon (OC), total nitrogen (N), bulk density, infiltration rate, bund height, and inter-terrace slope are significantly (p?0.05) affected by soil conservation measures. The non-conserved fields had significantly lower OC, total N, and infiltration rate; whereas higher bulk density as compared to the conserved fields with different conservation measures. However, no significant differences in bulk density were observed among the conservation methods. The field treated with 9-year old soil bund stabilized with tree lucerne or sole soil bund had significantly higher OC content than all other treatments. Fields having 6-year old soil bunds had lower OC and total N when compared to fields having 9-year old soil bunds irrespective of their method of stabilization. Fields with soil bunds stabilized with vetiver grass had the highest bund height and the lowest inter-terrace slope than fields with the remaining conservation measures. Barley grain and straw yields were significantly (P<0.05) greater in both the soil accumulation and loss zones of the conserved fields than the non-conserved (control) ones. In the accumulation zone, fields with the 9-year old soil bund stabilized with tree lucerne and those with the 9-year old sole soil bund gave higher grain yields (1878.5 kg ha-1 and 1712.5 kg ha-1, respectively) than fields having 9-year old soil bund stabilized with vetiver grass (1187 kg ha-1) and 6-year old soil bund stabilized with tree lucerne (1284.25 kg ha-1). When we compare the accumulation and the loss zones, the average grain yield obtained from the accumulation zones (averaged over all the Lessons from Upstream Soil Conservation Measures to Mitigate Soil Erosion and its Impact on Upstream and Downstream Users of the Nile River.Length: pp.170-183ErosionLand degradationSoil conservationBundsWater conservationSoil properties

Defect chemistry and transport properties of BaxCe0.85M0.15O3-d

The site-incorporation mechanism of M3+ dopants into A2+B4+O3 perovskites controls the overall defect chemistry and thus their transport properties. For charge-balance reasons, incorporation onto the A2+-site would require the creation of negatively charged point defects (such as cation vacancies), whereas incorporation onto the B4+-site is accompanied by the generation of positively charged defects, typically oxygen vacancies. Oxygen-vacancy content, in turn, is relevant to proton-conducting oxides in which protons are introduced via the dissolution of hydroxyl ions at vacant oxygen sites. We propose here, on the basis of x-ray powder diffraction studies, electron microscopy, chemical analysis, thermal gravimetric analysis, and alternating current impedance spectroscopy, that nominally B-site doped barium cerate can exhibit dopant partitioning as a consequence of barium evaporation at elevated temperatures. Such partitioning and the presence of significant dopant concentrations on the A-site negatively impact proton conductivity. Specific materials examined are BaxCe0.85M0.15O3-d (x = 0.85 - 1.20; M = Nd, Gd, Yb). The compositional limits for the maximum A-site incorporation are experimentally determined to be: (Ba0.919Nd0.081)(Ce0.919Nd0.081)O3, (Ba0.974Gd0.026)(Ce0.872Gd0.128)O2.875, and Ba(Ce0.85Yb0.15)O2.925. As a consequence of the greater ability of larger cations to exist on the Ba site, the H2O adsorption and proton conductivities of large-cation doped barium cerates are lower than those of small-cation doped analogs

Promoting global watershed management towards rural communities: the May Zeg-zeg initiativeLength: pp.192-195

Watershed managementRural development

Determination of Local Barley (Hordeum Vulgare) Crop Coefficient and Comparative Assessment of Water Productivity for Crops Grown Under the Present Pond Water in Tigray, Northern Ethiopia

An experiment was carried out in 2010 at Mekelle, in northern Ethiopia, to measure the evapotranspiration, to estimate barley crop coefficient (kc), and to evaluate the water productivity taking into account the major crops grown under the present pond irrigation system. Four locally made lysimters were installed in the middle of barley field to measure barley evapotranspiration. The single crop coefficient approach was used to estimate barley crop coefficient. The average seasonal evapotranspiration of barley was 375 mm which is similar to many other cereal crops in the region. The single crop coefficient values for early, vegetative, mid and late crop stages were 0.6 – 0.8, 0.6 – 1.0; 1.0 – 1.05 and 0.3 - 0.4 respectively. The result showed that these crop coefficient values obtained in this experiment were similar to the crop coefficient values obtained in the past except for kc initial. Therefore, the assumption that local barley crop coefficient values differ from that of the documented values was incorrect. Furthermore, the major reason for mismanagement of irrigation water in barley fields was not due to use of wrong crop coefficient values but could be due to inadequate irrigation technical skill and knowledge of the farmer. The average economic water productivity (EWP) of barley for the very wet, wet, normal, dry and very dry seasons scenario were 0.99, 0.7, 0.65, 0.57, and 0.44 USD m-3, respectively, whereas the corresponding crop water productivity (CWP) values for grain were 1.53, 1.08, 1.0, 0.88 and 0.68 kg m-3, respectively. The EWP and CWP of barley were compared with onion and tomato under pond water irrigation at the five climatic scenarios. The crop water productivity for tomato and onion were 85 – 87% and 76 – 78% higher than that of barley, respectively. The corresponding economic water productivity for tomato and onion were 87 – 89% and 81 – 82% higher than that of barley, respectively. We concluded that growing tomato and onion would bring more income or yield per m3 of pond water supplied than growing barley. The implication is that as supply and demand determines the price of products, farmers and extension workers need to balance the crop area coverage per irrigation scheme so that undesirable price falls and rises could be avoided. Evaluation of crops based on their water productivity would improve the productivity of irrigation schemes and ultimately improve food security in the arid and semi-arid areas where water scarcity is critical problem and irrigation is a necessity for crop production. Key Words: Barley, Evapotranspiration, Crop coefficient, Water productivity

Pressure-induced amorphization, crystal-crystal transformations and the memory glass effect in interacting particles in two dimensions

We study a model of interacting particles in two dimensions to address the relation between crystal-crystal transformations and pressure-induced amorphization. On increasing pressure at very low temperature, our model undergoes a martensitic crystal-crystal transformation. The characteristics of the resulting polycrystalline structure depend on defect density, compression rate, and nucleation and growth barriers. We find two different limiting cases. In one of them the martensite crystals, once nucleated, grow easily perpendicularly to the invariant interface, and the final structure contains large crystals of the different martensite variants. Upon decompression almost every atom returns to its original position, and the original crystal is fully recovered. In the second limiting case, after nucleation the growth of martensite crystals is inhibited by energetic barriers. The final morphology in this case is that of a polycrystal with a very small crystal size. This may be taken to be amorphous if we have only access (as experimentally may be the case) to the angularly averaged structure factor. However, this `X-ray amorphous' material is anisotropic, and this shows up upon decompression, when it recovers the original crystalline structure with an orientation correlated with the one it had prior to compression. The memory effect of this X-ray amorphous material is a natural consequence of the memory effect associated to the underlying martensitic transformation. We suggest that this kind of mechanism is present in many of the experimental observations of the memory glass effect, in which a crystal with the original orientation is recovered from an apparently amorphous sample when pressure is released.Comment: 13 pages, 13 figures, to be published in Phys. Rev.

Regionalisation for lake level simulation – the case of Lake Tana in the Upper Blue Nile, Ethiopia

In this study lake levels of Lake Tana are simulated at daily time step by solving the water balance for all inflow and outflow processes. Since nearly 62% of the Lake Tana basin area is ungauged a regionalisation procedure is applied to estimate lake inflows from ungauged catchments. The procedure combines automated multi-objective calibration of a simple conceptual model and multiple regression analyses to establish relations between model parameters and catchment characteristics. &lt;br&gt;&lt;br&gt; A relatively small number of studies are presented on Lake Tana's water balance. In most studies the water balance is solved at monthly time step and the water balance is simply closed by runoff contributions from ungauged catchments. Studies partly relied on simple &lt;i&gt;ad-hoc&lt;/i&gt; procedures of area comparison to estimate runoff from ungauged catchments. In this study a regional model is developed that relies on principles of similarity of catchments characteristics. For runoff modelling the HBV-96 model is selected while multi-objective model calibration is by a Monte Carlo procedure. We aim to assess the closure term of Lake Tana's water balance, to assess model parameter uncertainty and to evaluate effectiveness of a multi-objective model calibration approach to make hydrological modeling results more plausible. &lt;br&gt;&lt;br&gt; For the gauged catchments, model performance is assessed by the Nash-Sutcliffe coefficient and Relative Volumetric Error and resulted in satisfactory to good performance for six, large catchments. The regional model is validated and indicated satisfactory to good performance in most cases. Results show that runoff from ungauged catchments is as large as 527 mm per year for the simulation period and amounts to approximately 30% of Lake Tana stream inflow. Results of daily lake level simulation over the simulation period 1994–2003 show a water balance closure term of 85 mm per year that accounts to 2.7% of the total lake inflow. Lake level simulations are assessed by Nash Sutcliffe (0.91) and Relative Volume Error (2.71%) performance measures

Synthesis, Structure, and Properties of Compounds in the NaHSO_4−CsHSO_4 System. 1. Crystal Structures of Cs_2Na(HSO_4)_3 and CsNa_2(HSO_4_)3

Exploratory synthesis in the NaHSO₄-CsHSO₄ system, aimed at discovering novel proton conducting solids, resulted in the new compounds CsNa₂(HSO₄)₃ and Cs₂Na(HSO₄)₃. Single-crystal X-ray diffraction (performed at room temperature) revealed CsNa₂(HSO₄)₃ to crystallize in the cubic space group P2₁3 with lattice parameters a=10.568(2)Å and Z=4, whereas CS2Na(HSO₄)₃, studied by both single-crystal neutron and X-ray methods, crystallizes in the hexagonal space group P6₃/m. The latter compound has lattice parameters a=8.5712(17) and c=9.980(2)Å, and Z=2. The unit cell volumes are 1180.4(4) and 634.9(2)ų, respectively, giving calculated densities of 2.645 and 3.304 mg m⁻³. Refinement using all observed reflections yielded a weighted residual, R-w(F²), of 0.0515 based on F² X-ray values for CsNa₂(HSO₄)₃. For Cs₂Na(HSO₄)₃ the analogous X-ray and neutron values were 0.0483 and 0.1715, respectively. Both structures contain a single, crystallographically distinct, asymmetric hydrogen bond (as confirmed by NMR investigations) and unique, three-membered (HSO₄)₃ rings. The geometric match between the NaO₆ octahedra and the rings suggests the sodium polyhedra may serve to template the (HSO₄)₃ unit. In CsNa₂(HSO₄)₃ the rings form a distorted cubic close-packed array. The Cs atoms are located within the "octahedral" sites of this array, and the Na atoms, within the "tetrahedral" sites. The rings in CS₂Na(HSO₄)₃ are linked together by NaO6 octahedra to form infinite Na(HSO₄)₃ chains that extend along 001. The hexagonal compound exhibits disorder about the sulfate tetrahedron that suggests a P6₃/m → P6 phase transition may occur upon cooling

Single-crystal neutron diffraction study of β-Cs_3(HSO_4)_2[H_(2-x)(S_xP_(1-x)O_4] (x ≃ 0.5) at 15 K

The structure of β-Cs_3(HSO_4)_2[H_(2-x)(S_xP_(1-x)O_4] has been examined by single-crystal neutron diffraction at 15 K. The compound crystallizes in space group C2/c and contains four formula units in the unit cell, with lattice parameters a = 19.769(9), b = 7.685(2), c = 8.858 (3) Å and β = 100.60 (4)°. Refinement of P, S and H site occupancies indicated that the value of x (in the stoichiometry) is 0.500 (6). This, together with the unit-cell volume of 1322.8(14) Å^3, implies a density of 3.463 Mg m^(-3). The structure contains zigzag rows of XO_4 anions, where X = P or S, that alternate, in a checkerboard fashion, with zigzag rows of Cs cations. Moreover, there is one proton site, H(3), with an occupancy of 0.25 and one X-atom site, X(1), that is occupied by 0.5 P and 0.5 S. These features are in general agreement with a previous X-ray structure determination carried out at 298 K. In contrast to the X-ray study, however, it was found that two different structural models adequately fit the diffraction data. In the first model, the proton vacancies and the P atoms were assumed to be randomly distributed over the H(3) and X(1) sites, respectively, and to have no impact on the local structure. In the second model, several atoms were assigned split occupancies over two neighboring sites, to reflect the presence or absence of a proton vacancy, and the presence of P or S on the X(1) site. Refinement assuming the first model, in which anisotropic displacement parameters for 12 of 14 atom sites in the asymmetric unit were employed, yielded residuals wR(F^2) = 0.084 and wR(F) = 0.038. For the second model, in which anisotropic displacement parameters were utilized for only the five atoms that were not split relative to the first model, the residuals were wR(F^2) = 0.081 and wR(F) = 0.036