Can highly saline irrigation water improve sodicity and alkalinity in sodic clayey subsoils?

Purpose

The concept of irrigating crops with saline irrigation water is not new, but impacts of this practice on soil properties remain debatable, particularly the use of highly saline water. In this work, key soil chemical properties were assessed to a depth of 300 cm following 2.5 years of application of highly saline irrigation to a sodic texture-contrast soil (Brown Sodosol) in south-eastern Tasmania, Australia.

Materials and methods

Control plots (rainfall only) were compared to irrigation treatments of low (0.8 dS/m) and high salinity (16 dS/m) waters at application rates of both 200 and 800 mm/year.

Results and discussion

Whilst significant increases in both electrical conductivity and chloride concentration occurred throughout the soil profile in the high salinity treatment, these values were well below those of the irrigation water, indicating effective deep leaching. In the upper soil profile, 0–50 cm, of the high salinity treatments both the exchangeable Na⁺ and its ratio to total base cations (ESP) were significantly increased whilst the lower soil profile between 50 and 200 cm, was improved via both reduced alkalinity and sodicity. Leaching of the exchangeable base cations Ca²⁺, Mg²⁺ and K⁺ was significant in the upper soil profile (0–50 cm). As expected, the low salinity treatment (0.8 dS/m) had minimal impacts on soil chemical properties. The upper topsoil (0–10 cm) total organic carbon was significantly reduced in the high salinity plots and was negatively correlated with Cl^? concentration.

Conclusions

The data confirms the general concerns about application of saline irrigation, namely increased whole profile salinisation and upper soil profile (0–50 cm) sodicity, but they also show unexpected and desirable reductions in the lower soil profile (>?50 cm) alkalinity and sodicity. It appears the Na⁺ ions present in the saline waters led to differential leaching of base cations from the rooting zone, especially Ca²⁺ which then ameliorate the alkalinity and sodicity deeper in the soil profile (>?50 cm). Thus, surface application of gypsum may help sustain the application of highly saline waters; alternatively, subsurface irrigation above the sodic clayey subsoils could be trailed.

     

Pikeperch (Sander lucioperca) spermatozoa motility and volume regulation under different osmotic and ionic conditions

Fish Physiology and Biochemistry - Pikeperch (Sander lucioperca) is a highly profitable commercial species whose economic value has greatly increased in the last decade. As in other species, the...     

Bioremediation of Oil Sludge in Shengli Oilfield

Large quantity of dehydrated oil sludge, generated in the disposal process of oil-containing sewage in Shengli oilfield, needs to be rendered harmless to human and to the environment. Bioremediation has been accepted as an important method for the treatment of oil sludge by employing indigenous or extraneous microbial flora. The bioremediation of a dehydrated oil sludge of 960 m³ in volume was carried out in a prepared bed in Binyi oil-containing sewage disposal station, Shengli oil fields, China. Four different treatments were made to study the impact of certain process parameters on the bioremediation efficiency. Of the oil contaminants, 52.75% was degraded within 160 days when treated in a greenhouse, while the oil contaminations decreased by only 15.46% in the untreated sludge. The variations of the physical and chemical properties of oil sludge, the amount and the functional diversity of microorganisms in sludge were characterized. The results indicated that the water-holding capacity of oil sludge, the amount and the metabolism functional diversity of microorganisms in sludge in the three treatments increased markedly compared with the control.     

Dry Deposition of Atmospheric Sulphur and Nitrogen in Russia and the Former USSR

Generally, dry deposition processes are very important for atmospheric chemistry of pollutants providing up to 30–80 % of the removal for certain compounds from the atmosphere. The model for calculating of dry deposition fluxes for a large territory seems unsophisticated in spite of the dependence on surface characteristics, pollutant properties and atmospheric conditions. The approach of combining monthly average concentrations measured at the Integrated Background Monitoring Network (IBMoN) and EMEP stations and linear dry deposition velocity was used to calculate total sulphur and nitrogen fluxes for the whole of the former Soviet Union (FSU) taking into account large-scale geographical variability in climate and lands. Most values of all SO₂ and SO₄ ^2? concentrations were below 2.9 and 3.1 mgS/m³, and NO₂ concentration were 1.5 mgN/m³ over European part and 0.6 mgN/m³ in Western Siberia. The long-term trends of oxidised sulphur and nitrogen compounds in the atmosphere were examined for 1982–1998 in certain FSU regions. Annual dry deposition of sulphur was estimated as 3.64 Mt S (in sulphate form) and 2.76 Mt S (in SO₂ form) for the whole area of FSU. Annual removal of NO₂ by dry deposition was calculated at 1.27 Mt N. These values constituted between 44 and 50% of total oxidised sulphur and nitrogen deposition.     

Climate variability during the past 2,000 years and past economic and irrigation activities in the Aral Sea basin

The lake level history, here based on the relative abundance of Ca (gypsum), is used for tracing past hydrological conditions in Central Asia. Lake level was close to a minimum before approximately a.d. 300, at about a.d. 600, a.d. 1220, a.d. 1400 and since 1960s it is lowering again. Lake water level was lowest during the fourteenth or early fifteenth centuries as indicated by a coeval settlement, which today is still under water near the well-dated mausoleum of Kerderi. Pollen data from riparian vegetation indicate generally wet conditions between a.d. 400 and a.d. 900, intermitted by short intervals with drier conditions (AD 550–600; a.d. 650–700) and riverbanks were again dry from a.d. 900–1150, a.d. 1450–1550, and from a.d. 1970 onward moisture decreased steadily. Irrigation activities were at a maximum between 300 b.c. and a.d. 300 (Classical Antiquity) and between a.d. 800 and a.d. 1300 (Medieval Age) and after a.d. 1960.     

A unique genotype of Leptospira interrogans serovar Pomona type kennewicki is associated with equine abortion

Although serologic data indicate horses in N. America are exposed to a variety of leptospiral serovars, abortion is almost always associated with Leptospira interrogans serovar Pomona type kennewicki. A variety of wildlife including raccoons, white tailed deer, striped skunks, opossums, and red and grey foxes have been shown to host serovar Pomona and have therefore been suspect as sources of infection for pregnant mares. The aim of the present study was to examine genetic diversity in serovar Pomona type kennewicki in wildlife and in aborting mares. Our approach utilized PCR that targeted tandem repeats at the VNTR - 4 locus and a 1235 bp 5'-sequence of the lk73.5 (sph2) and adjacent upstream sequence unique to serovar Pomona. All isolates/specimens of equine origin in 1992 and 2008 yielded amplicons of 1235 and 595 bp, whereas 14 isolates/specimens from wildlife yielding a 1235 bp amplicon characteristic of serovar Pomona produced amplicons of 1300, 550 bp (3), 1300 bp (10), or 595 bp (6) with the VNTR - 4 primer set. Wildlife therefore hosted at least three different genetic variants of type kennewicki including the genetic variant that predominated in aborting mares. The data are consistent with other studies indicating specific genetic variants of type kennewicki show a strong tendency to be associated with a specific host. Levels of antibody in wildlife sera reactive with rLk73.5, rLig130 and sonicate of type kennewicki were poorly correlated with PCR data, although rLk73.5 was superior to rLig130 in detection of antibody responses. PCR is therefore a more reliable tool for studies of wildlife reservoirs of Leptospira sp. than serologic surveillance that targets host induced proteins or LPS-rich sonicate.     

Stellar feedback in dwarf galaxy formation

Dwarf galaxies pose substantial challenges for cosmological models. In particular, current models predict a dark-matter density that is divergent at the center, which is in sharp contrast with observations that indicate a core of roughly constant density. Energy feedback, from supernova explosions and stellar winds, has been proposed as a major factor shaping the evolution of dwarf galaxies. We present detailed cosmological simulations with sufficient resolution both to model the relevant physical processes and to directly assess the impact of stellar feedback on observable properties of dwarf galaxies. We show that feedback drives large-scale, bulk motions of the interstellar gas, resulting in substantial gravitational potential fluctuations and a consequent reduction in the central matter density, bringing the theoretical predictions in agreement with observations.     

Strong, transparent, multifunctional, carbon nanotube sheets

Individual carbon nanotubes are like minute bits of string, and many trillions of these invisible strings must be assembled to make useful macroscopic articles. We demonstrated such assembly at rates above 7 meters per minute by cooperatively rotating carbon nanotubes in vertically oriented nanotube arrays (forests) and made 5-centimeter-wide, meter-long transparent sheets. These self-supporting nanotube sheets are initially formed as a highly anisotropic electronically conducting aerogel that can be densified into strong sheets that are as thin as 50 nanometers. The measured gravimetric strength of orthogonally oriented sheet arrays exceeds that of sheets of high-strength steel. These nanotube sheets have been used in laboratory demonstrations for the microwave bonding of plastics and for making transparent, highly elastomeric electrodes; planar sources of polarized broad-band radiation; conducting appliqués; and flexible organic light-emitting diodes.