Sandy Desert Soils Research Articles

Environmental conditions and soils of natural oases in the Alashan Gobi Desert, Mongolia

Environmental conditions and soils of nine natural oases in the Alashan Gobi Desert of Mongolia are characterized. All these oases are allocated to the zones of tectonic faults, where the discharge of slightly saline groundwater takes place. The absolute heights are about 1500 m a.s.l. The oases are found on piedmont plains or in hilly areas occupied by true deserts with fragments of extremely arid deserts. With respect to geomorphological conditions, four types of oases can be distinguished: isolated (isle-type) oases, oases in large mesodepressions, oases formed in naturally ponded areas, and oases within terraced valleys. Each of these types is characterized by specific soil cover patterns controlled by the geomorphological features of the territory, the character of parent materials, and the groundwater depth. At the same time, some common soil properties are typical of all the oases. Hydromorphic soils—peat meadow-swampy soils, dark-colored nonsaline meadow soils, oasis solonchaks that developed in areas with shallow nonsaline groundwater, solonchaks with different degrees of hydromorphism that developed from mottled-colored salt-bearing Cretaceous and Paleogene deposits, and soddy alluvial (floodplain) soils—predominate in the central parts of the oases. Under conditions of deep groundwater, takyric and sandy desert soils are formed. The oases are encircled by desert ecosystems with gray-brown desert and extremely arid soils and with poorly developed stony soils that formed on the low residual mounts. In the period of the study (1991), irrigated farming was only developed within one of the studied oases. The main part of the land was used for pasturing. In some cases, the high grazing pressure led to degradation (desertification) of oasis ecosystems. A comparison of the oases studied in the Alashan Gobi with the Ekhiin-Gol oasis in the Transaltai Gobi attests to the similarity of their nature.

The change in soil cover on the exposed bed of the Aral Sea

Desiccation of the Aral Sea has led to the formation of new soil cover on the exposed seabed. Investigation of the newly formed dry land is very important since it is a source of dust storms and salts transferred to long distances. A soil map of the exposed seabed for 2000 has been produced on the basis of the map for the year 1990 (Institute of Soil Science, Uzbekistan), satellite images, and selected field observations of groundwater table. During the period 1990–2000, the sea recessed 20–32 km, thus changing the soil cover characteristics. The maps of soil cover with the detailed information on soil textures, the characterization of soil types, the soil formation trends, and the changes in soil types during the sea recession process are available. Attention has been paid to erosion tendencies and susceptibility to dust and salt transfers. As a whole, the soil cover was formed as a result of the replacement of excessive wetlands (salt-marsh), located in the form of strip along the sea, by hydromorphic and semi-hydromorphic, semi-automorphic and automorphic soils. The drying seabed has complicated lithological and morphologic composition. The territory of the exposed seabed is characterized by different hydrological conditions. Groundwater depth varies from 0.5 to 10 m. With the shore's recession, the water storage groundwater is approaching the surface. With general tendency towards desertification, the initial soil cover changes. The soils that did not reach the complete genetic formation, under the influence of quickly changing hydrogeological conditions, are transformed into the other types and subtypes. Often, while becoming dry, they are self-destructed and change into sands. Currently, the following types of soils are observed on the exposed seabed: automorphic solonchaks, semi-automorphic solonchaks, semi-hydromorphic solonchaks, hydromorphic solonchaks, desert sandy soils, sands.

Retention of copper by desert sands coated with ferric hydroxides

Due to the sandy character of the desert sandy soils, surface reactivity and hence adsorption of micronutrients are very low. Therefore, different fractions from sand particles were coated with four partially hydroxylated ferric sols of OH/Fe molar ratio of 1.00, 1.50, 2.00, and 2.84. The obtained results prove that the extractability of iron is reduced by increasing the OH/Fe molar ratio before its addition to the sand particles. Iron oxide coating of sand particles increased the amount of Cu adsorbed as compared with uncoated ones. With regard to the effect of polymerization degree of ferric sols, results show that decreasing OH/Fe molar ratio of iron sols enhanced the Cu adsorption maximum capacity, as calculated from the Langmuir equation. The amount of adsorbed Cu increased by decreasing the size of sand particles. Moreover, increasing the pH value of Cu equilibrium solution from 4.5 to 7.5 resulted in more adsorption of Cu by ferric hydroxide-coated sand particles.

Disturbance of biological soil crusts: impacts on potential wind erodibility of sandy desert soils in southeastern Utah

Friction threshold velocities (FTVs) were determined for biological soil crusts in diAerent stages of recovery. Particles on the surface of crusts that had been relatively undisturbed for at least 20 years were found to have significantly higher FTVs than those that had been disturbed 5, 10 or 1 years previously (376, 87, and 46 cm sec ˇ1 , respectively). FTV’s for crust breakage was also much higher for undisturbed crusts when compared to the previously disturbed crusts (573, 148, and 88 cm sec ˇ1 , respectively). All crusted surfaces were more stable than bare sand, which had an FTV of 16 cm sec ˇ1 . Disturbance treatments were then applied to the three crustal classes. Disturbance significantly reduced the FTVs of all classes by 73‐92 per cent. Comparing crustal FTVs with mean and high monthly wind speeds found in this region, it was observed that only crusts that had been undisturbed for approximately 20 years or more were able to protect soil surfaces from wind gusts expected on the average of once a month. Other crustal classes, as well as all disturbance treatments, had FTVs lower or equal to that of commonly occurring winds in this region. Because most of the crustal biomass occurs in the top 0.3 mm of soils, even slight soil loss can negatively influence stability and nutrient inputs to this ecosystem. #1997 John Wiley & Sons, Ltd.

Physiological and chemical responses of sunflower to the application of previous organic waste composts to sandy soil

Describes field experiments to determine the effects of previous organic waste composts, using different types and application rates, on sunflower yield. Oil, carbohydrates and metal content were evaluated. Experiments were conducted in the Nuclear Research Centre Farm, in sandy, infertile soil. Results show a remarkable increase in dry matter and seed yields, due to previous single compost additions. A mixture of water hyacinth and biosolid compost showed an improvement. The results of this research indicate that application of organic waste composts is a feasible and valuable recycling method in sandy desert soils.

Soil radioactivity atlas of Kuwait

Background radionuclide concentrations in surface soil (5 cm loop) across Kuwait were measured by gamma spectroscopy with a HPGe detector. These measurements were made as part of a program for assessment of radiation doses from natural sources for the Kuwait population. The sampling program provided background information at 83 sites in different geological formations. The nationwide average concentrations in Bq/kg were as follows: for 40K - 332 ± 104 Bq/kg (arithmetic 50), for 226Ra - 11.8 ± 4.0 Bq/kg, for 238U - 13.3 ± 5.0 Bq/kg, for 232Th - 10.0 ± 3.4 Bq/kg, and for 137Cs - 2.6 ± 2.6 Bq/kg. The average concentrations of 232Th and 238U radionuclides were lower than the world average since a large area of Kuwait is covered with desert sandy soil. In most cases, the daughter radionuclides of uranium and thorium series were found almost in radioactive equilibrium. On the basis of these measurements and dose rate per unit concentration in soil adopted from UNSCEAR (1989), the average absorbed dose rate in the air (at 1 m height) from the gamma field of primordial radionuclides was estimated at 0.23 mGy per y for Kuwait.

Mobility of oil and other sludge constituents during oily sludge treatment by landfarming

Five levels of oily sludge application were made to the surface layer of a desert sandy soil in Kuwait. The migration of the constituents of the sludge to subsurface soil layers was investigated at intervals over a period of 29 months. The data show very limited mobility to subsurface soil layer (40–70 cm depth) but not to 70–90 cm depth. The environmental impact of the added sludge is related to soil pH and to the Zn equivalent value of the sludge. Zn equivalent for the soil treated with oily sludge was 612 mg kg −1, which is much lower than permissible limits. This soil can accept more than 1000 t ha −1 from this type of sludge. However, due to the heterogeneous composition of sludge the Zn equivalent value should be calculated for each batch. Addition of oily sludge to the desert soil susceptible to wind erosion had a significant effect on minimizing soil loss under wind tunnel conditions. This effect is attributed to aggregation of the soil particles in the surface soil layers.

Effect of bitumen mulch on the growth of garlic under different field conditions

Summary A field experiment was conducted on garlic plants grown in a desert sandy soil treated with bitumen emulsion as a soil conditioner at 0 and 50 g/m 2 , under drip irrigation. Three different irrigation intervals (2, 3 and 4 days) and two planting densities (2 and 4 rows per dripline) were compared. Bitumen mulch had a positive effect on individual plant weight and obtainable yield, regardless of the number of plantrows (2–4 rows), under the 4 day interval. The 2 day irrigation interval had only a positive effect on the germination per cent under the 4 row density. Total yield, individual plant weight and bulb characteristics were best under the 3 day irrigation interval and 4 row planting density. The highest water use efficiency was obtained under the 4 day irrigation interval and 4 row density. Doubling the number of rows per dripline reduced the individual plant weight and had only little effect on the yield. Bulb characteristics were not affected by increasing the density. Yield of air dry bulbs increased due mainly to higher number of plants. Water use efficiency was positively influenced by doubling the plant rows per dripline. An irrigation interval of 3 days with a 4 row density gave the best results from most points of view. Bitumen application has some positive effects under higher water stress conditions.

Water retention and nutrient availability in a fly ash amended desert sandy soil: A studyin vitro

Abstract The effect of fly ash application on some physicochemical properties of a desertic sandy soil was examined under laboratory conditions. Fly ash collected from two sources, that is, directly from an electric precipitator and an old deposit, were mixed with soil each at 0, 8, and 15% and maintained moist at 50% field capacity. After one month, the treated soil was analyzed for moisture retention characteristics, available nutrients, and phosphate adsorption. Addition of fly ash resulted in a considerable improvement in available water holding capacity and a marginal increase in available N, P, K, Fe, Mn, Zn, and Cu of the sandy soil. Adsorption maxima of phosphates increased while the bonding energy constant decreased due to addition of fly ash. Fly ash collected directly from the electric precipitator was more effective in improving the moisture retention capacity and available nutrient status of the sandy soil.

Reduction of ammonia volatilization from urea by rapid nitrification

Abstract Loss of NH3 from urea fertilizer in a cultivated sandy desert soil was evaluated by using various fertilizer treatment regimes. The nitrification of added urea increased with the pretreatment of (NH4)2SO4. The increase in nitrification rate was directly related to the amount of (NH4)2SO4 added. These results suggested that when urea was applied after sufficient increase in nitrification rate, i.e., 3 to 5 weeks after the pretreatment with NR+ 4 fertilizers, the NH+ 4 produced by the hydrolysis of urea was quickly nitrified, leaving low concentration of NH+ 4 in soil and resulting in decreased losses of NH3. Among the different NH+ 4 containing or forming fertilizers, (NH4)2SO4 was significantly better in arresting NH3 loss from a subsequent application of urea. The decreased loss of N was reflected in higher yields of pearl millet.

Salts in sandy desert soils, southwestern Egypt

Different sandy soils,derived from mesozoic sandstone and pleistocene dune sands in the southwestern desert of Egypt, have been examined referring to the distribution of water soluble salts. Despite a low groundwater table (>25 m) and a very low mean annual rainfall (<1 mm) the salt contents are maximal in the subsoil. The salt composition is clearly related to soil depth and temperature and influenced by sodium adsorption. With soil depth the solubility of the salts increase, so that enrichment and distribution of salts here are both caused by rainfall. The results have been discussed for present and former climatic conditions and it was assumed that this type of salinization is caused by episodic rainstorms of the subrecent time.

Some studies on hydrothermal regime and daytime heat fluxes in a desert sandy soil with and without vegetation

The results of the studies conducted during 1977–78 show higher moisture regime of a bare sandy soil of Jodhpur than the soil with vegetative cover. Mean maximum temperature of a bare soil at 5 cm depth, in general, was 1 to 2°C higher than the soil with vegetative cover except during July when there was considerable fall in temperature of a bare soil. Daytime soil temperatures at 5 cm depth during summer were higher than the lower depths leading thereby to downward movement of heat. In winter, however, the temperatures of lower layers were higher facilitating the upward flow of heat and the vapour flux. A high variability in heat fluxes with generally positive daytime heat fluxes in summer and negative in winter were observed.

Use of an asphalt subsurface barrier for improving the productivity of desert sandy soils

Field studies were conducted during 1974–8 to determine the effect of an asphalt subsurface barrier 2 mm thick at a depth of 60 cm on crop production, water and nitrogen conservation. The results showed 100 per cent increase in moisture and nitrogen retention. This led to an average increase in the production of pearl millet (Pennisetum typhoides) of 40–60 per cent.