Salt-affected land achievements

Letter to the editor from C.V. Malcolm, Research officer, Soils Division, Department of Agriculture, South Perth. Mr. Malcolm address the letter by L.S. Walder in the June 2 issue, where L.S. Walder applauds Mr. Whittington's soil reclamation efforts and infers that he has returned a severe salt-affected property from which a livelihood was being threatened by salt to one of high production, and recommends the use of such techniques throughout the agricultural areas. Mr. Malcolm attempts to clarify the issues, listing the achievements of Mr. Whittington and his efforts involving soil conservation measures. The principles Mr. Whittington adopted are recommended by the Department of Agriculture but the details of bank design differ. The Whittington interceptor banks are large and expensive and need to be well maintained to avoid being damaged by heavy rain. PLEASE NOTE: We are unable to provide a public view of this newspaper article as the copyright is held by the publisher of The New Mercury. If you would like to obtain a copy of this newspaper article for research purposes, please ‘request a copy'. This article is part of the WISALTS (Whittington Interceptor Sustainable Agriculture Land Treatment Society Incorporated) Collection

Increased concentrations of chloride beneath stands of saltbushes (Atriplex species) suggest substantial use of groundwater

This paper examines the accumulation of soil chloride and the increase in electrical conductivity of the groundwater beneath stands of saltbushes (Atriplex species) in a plant spacing trial conducted near Keller berrin in Western Australia. The trial had a randomised block design with 5 plant spacings (1 by 1 m,1 by 2 m, 2 by 2 m, 2 by 3 m, and 3 by 3 m), 5 saltbush species (Atriplex undulata D. Dietr., A. amnicola Paul G. Wilson, A. vesicaria Heward ex Benth., A. paludosa R. Br. and A. bunburyana F. Muell.) and 3 replicate plots (each consisting of 25 plants in 5 by 5 array). The saline groundwater at the site was between 0.5 and1.2 m below the surface for the duration of the experiment. Over a 2-year period there was a substantial increase in soil chloride concentration beneath the saltbushes. These increases were proportional to salt bush ‘leaf density’ (weight per unit soil surface area) and inversely proportional to the initial concentration of chloride in the soil. There was a substantial increase in the electrical conductivity of the groundwater which was also proportional to ‘leaf density’. It is argued that the increases in soil salinity and groundwater electrical conductivity were primarily due to the use of groundwater by the saltbush stands. Salt accumulation data suggest that about 60–100 mm of groundwater was used (transpiration and evaporation) over the 2 years. These results are discussed in terms of the ability of saltbushes to lower local water tables, thereby making saline soils better suited to the growth of superior annual pasture species

Agriculture on saline soils: Direction for the future

No abstract availabl

Forage and fuel production from salt affected wasteland.

This book is the proceedings of a seminar held at Cunderdin on 19-27 May 1986 and is reprinted from Reclamation and Revegetation Research Vol. 5 Nos. 1-3. Reports of several aspects of forage and fuel production on saline soils are given from 16 different countries. Papers are presented under the following headings: salt affected wasteland: nature and distribution; salt tolerant plant resources; production from salt affected soil; establishment problems and methods; and utilization, management and social aspects. Relevant papers are abstracted separately

Comparison of three techniques for revegetating salt affected land with halophytes

No abstract availabl

Halophyte and glycophyte salt tolerance at germination and the establishment of halophyte shrubs in saline environments

Saline sites suffer variations in surface salinity, available soil water, temperature, soil crust strength and other factors which can influence germination and establishment. For establishment to occur the germinating seed must capitalise on a window of opportunity. This window can be widened by placing seeds in a low-salt niche, covering the seeds with a mulch (such as vermiculite), spraying the seed and mulch placement with a coating which may stabilise the favourable situation and raise soil temperature. In this paper it is shown that using seeds collected from plants of Atriplex amnicola which produce many volunteer seedlings in their vicinity can assist establishment from direct seeding. These seeds had the ability to germinate under saltier and cooler conditions than seeds from A. amnicola bushes which did not produce volunteers. Seeds of a halophyte (Atriplex lentiformis) and a non-halophyte (Medicago sativa) are able to imbibe water from a saline substrate in a similar manner. The water enables the seeds of both species to mobilise stored growth materials and produce and elongate radicles. When the seedlings try to erect a hypocotyl and spread their cotyledons, the non-halophyte, in a saline medium, becomes flaccid, distorted and dies. The halophyte seedling shows evidence of high salt tolerance in the form of succulence of cotyledons and trichomes on true leaves even before they are visible and goes on to successfully develop a functioning plant. Nevertheless, germination of halophyte seeds is inhibited or severely reduced at salinity levels above 250 mM NaCl and slowed and reduced progressively up to those levels

Phase curve and geometric albedo of WASP-43b measured with CHEOPS, TESS, and HST WFC3/UVIS

Context. Observations of the phase curves and secondary eclipses of extrasolar planets provide a window onto the composition and thermal structure of the planetary atmospheres. For example, the photometric observations of secondary eclipses lead to the measurement of the planetary geometric albedo, Ag, which is an indicator of the presence of clouds in the atmosphere. Aims. In this work, we aim to measure the Ag in the optical domain of WASP-43b, a moderately irradiated giant planet with an equilibrium temperature of ~1400 K. Methods. For this purpose, we analyzed the secondary eclipse light curves collected by CHEOPS together with TESS along with observations of the system and the publicly available photometry obtained with HST WFC3/UVIS. We also analyzed the archival infrared observations of the eclipses and retrieve the thermal emission spectrum of the planet. By extrapolating the thermal spectrum to the optical bands, we corrected for the optical eclipses for thermal emission and derived the optical Ag. Results. The fit of the optical data leads to a marginal detection of the phase-curve signal, characterized by an amplitude of 160 ± 60 ppm and 80a-? 50+60 ppm in the CHEOPS and TESS passbands, respectively, with an eastward phase shift of ~50 (1.5Ï ? detection). The analysis of the infrared data suggests a non-inverted thermal profile and solar-like metallicity. The combination of the optical and infrared analyses allows us to derive an upper limit for the optical albedo of Ag< 0.087, with a confidence of 99.9%. Conclusions. Our analysis of the atmosphere of WASP-43b places this planet in the sample of irradiated hot Jupiters, with monotonic temperature-pressure profile and no indication of condensation of reflective clouds on the planetary dayside.ISSN:0004-6361ISSN:1432-074

Large Interferometer For Exoplanets (LIFE): I. Improved exoplanet detection yield estimates for a large mid-infrared space-interferometer mission

One of the long-term goals of exoplanet science is the atmospheric characterization of dozens of small exoplanets in order to understand their diversity and search for habitable worlds and potential biosignatures. Achieving this goal requires a space mission of sufficient scale. We seek to quantify the exoplanet detection performance of a space-based mid-infrared nulling interferometer that measures the thermal emission of exoplanets. For this, we have developed an instrument simulator that considers all major astrophysical noise sources and coupled it with Monte Carlo simulations of a synthetic exoplanet population around main-sequence stars within 20 pc. This allows us to quantify the number (and types) of exoplanets that our mission concept could detect over a certain time period. Two different scenarios to distribute the observing time among the stellar targets are discussed and different apertures sizes and wavelength ranges are considered. Within a 2.5-year initial search phase, an interferometer consisting of four 2 m apertures covering a wavelength range between 4 and 18.5 μm could detect up to ~550 exoplanets with radii between 0.5 and 6 R⊕ with an integrated SNR≥7. At least ~160 of the detected exoplanets have radii ≤1.5 R⊕. Depending on the observing scenario, ~25-45 rocky exoplanets (objects with radii between 0.5 and 1.5 ⊕) orbiting within the empirical habitable zone (eHZ) of their host stars are among the detections. With four times 3.5 m aperture size, the total number of detections can increase to up to ~770, including ~60-80 rocky, eHZ planets. With four times 1 m aperture size, the maximum detection yield is ~315 exoplanets, including ≤20 rocky, eHZ planets. In terms of predicted detection yield, such a mission can compete with large single-aperture reflected light missions