Showing papers on "Soil salinity published in 1971"

Water Relations and Growth of Cotton as Influenced by Salinity and Relative Humidity1

Abstract: Soil salinity and atmospheric relative humidity influence plant growth, but few data are available showing the interaction between them. This interaction was studied with cotton (Gossypium hirsutum) in four sunlit climate chambers at temperatures cycling daily between 38 and 26 C. Relative humidity was controlled at 25, 40, 65, and 90%. The root medium was maintained at osmotic potentials of −0.4, −5, −10, and −15 bars. Relative humidity significantly affected shoot growth only in the 90% relative humidity treatment, where growth was increased about 40%. The shoot-to-root ratio at high humidities was at least double the ratio at low humidities. The 50% yield decrement based on leaf area or plant dry weight occurred at an osmotic potential of −5 bars. Because the anthers of the cotton flowers in the 25 and 90% relative humidity treatments did not dehisce, seed cotton yields at these relative humidities were essentially zero. Seed cotton yields per plant at 40 and 65% relative humidities were comparable to or greater than field yields. Transpiration per unit leaf area for the entire experiment increased an average of 80% for all salinity levels as the relative humidity decreased from 90 to 25% and decreased slightly with increasing salinity in all humidity treatments. Transpiration per unit leaf area decreased as the plants matured and tended to approach the same value for all treatments near the end of the experiment. The relative yield of dry matter and leaf area as a function of salinity was the same at all relative humidities, indicating that no interaction between salinity and relative humidity occurred.

Chemistry of Saline Soils and Their Physical Properties

Abstract: An outline of the forces involved in clay particle interaction (swelling and dispersion) is given as a background for the interpretation of the physical behaviour of sodic soils, especially in relation to electrolyte levels. The electrolyte concentration below which appreciable decreases in soil permeability are encountered has been termed the threshold concentration and this concentration increases with the degree of sodium saturation of the soil colloids. The application of the threshold concentration concept to the management and reclamation of sodic soil is discussed.

Reliability of Salinity Sensors for the Management of Soil Salinity1

Abstract: Laboratory-constructed and commercial salinity sensors were evaluated for stability of calibration and accuracy of measurement of soil salinity. Of the commercial sensors 85% were stable and performed satisfactorily for at least 1.5 years with an estimated accuracy of ± 0.6 mmho cm⁻¹. Laboratory-constructed sensors were accurate to ± 1 mmho cm⁻¹. Commercial sensors were used to monitor soil salinity in a field hi the Imperial Valley, demonstrating their value for salinity control. The salinity data revealed differences in water infiltration caused by surface topography and by the disturbance of soil during the installation of the sensor.

Shrub Ecotypes in a Salt Desert

Abstract: A SALINITY gradient extends from the highly saline beaches of the Great Salt Lake of Utah to the surrounding non-halomorphic soils, with a correlated vegetation gradient in which a succession of plant communities grows in concentric zones. The chief communities, in decreasing order of soil salinity, are dominated by (1) Salicornia–Allenrolfea; (2) Sarcobatus vermiculatus; (3) Atriplex–Eurotia; and (4) Artemisia tridentata1. Within these communities are perplexing local distributions of co-dominant species. Typical communities within the Atriplex–Eurotia zone include pure Atriplex confertifolia, Atriplex–Eurotia, pure Eurotia lanata, A. confertifolia Artemisia spinescens–Eurotia grass, and pure Atriplex nuttallii. Although these communities are separated by sharp ecotones, local soil variations are insufficient to explain the distribution of the different plant communities2.

Plant indicators in Iraq. I. Native vegetation as indicators of soil salinity and waterlogging

Abstract: SummaryEach of the major native halophytes was found to grow in soils with a definite range of total soluble salts. The descending ranking of the various species for soil salinity and ground water mineral content, when they were dominant, was:Halocnemum strobilaceum, Suaeda spp.,Seidlitzia rosmarinus, andCressa cretica. Salsola vermiculata indicates low salinity in sandy soils and low to high salinity in heavier soils.Prosopis farcta andAlhagi maurorum can grow in both saline and non-saline soils. As expected, non-halophytic communities were mostly found in the northern part of Iraq.All halophytes were found in soils with a ground water depth ranging from 0.6 to 2.0 meters, exceptSalsola vermiculata which could be used as an indicator of a ground water depth greater than 2 meters. Plant indicators of soil texture and recommendations concerning the possibility of reclaiming halophyte-inhabited soils are discussed.

Effects of Irrigation Water Temperature on Soil Temperature1

Abstract: Soil temperatures were measured in fields irrigated with normal and cold water and in unirrigated soil, to study the effects of irrigation water temperature on soil temperature. Temperatures were measured with probes made of thermocouple wire enclosed in 3 mm O.D. stainlesssteel tubing. The probes were inserted vertically into the soil. Errors in temperature measurement resulting from heat conduction along the probes were on the order of 0.1 C or less. The effects of irrigation water temperature on soil temperature were small and of short duration. Differences in soil temperature resulting from irrigation with water of 27 and 14 C lasted for less than 24 hours at 5 and 10 cm, and for 60 hours at 30 cm. Irrigated soil temperatures were significantly reduced by evaporative cooling from the soil surface after irrigation in mid-April, though not in mid-February.

Salinity and Water Use: Future Research Directions

Abstract: Future research directions in salinity at the molecular level are already predetermined, and will probably concern the details of ion pumping in cell membranes, the development of new antibiotics, the emergence of salt-tolerant plants and the like. The real problems lie in the catchments and will need the application of terrestrial field research for their solution. A brief analysis of the status of field research is presented and some reasons for its unpopularity are suggested. It is concluded that new research should concentrate on the location of saline soils, sediments and groundwaters more intensively than hitherto, on the origin of terrestrial salt, on the factors responsible for secondary salinity in soils, water supplies and irrigation areas, and on the criteria for evaluating salt-affected soils and techniques for their reclamation. There is acute need for research on the social consequences of a contracting population in irrigation enterprises that suffer partial failure.

Leaching of euphrates saline soil in lysimeters

Abstract: Summary A saline soil from Euphrates alluvium at Abu-Ghraib was leached in two lysimeters with river water and the changes in composition of the soils and of the leachates were measured as well as the hydraulic conductivity. The results show that the presence of gypsum prevents the soils becoming sodic as leaching with irrigation water of favourable composition proceeds.