Alluvial Clay Soil Research Articles

Enhancing NPK Uptake and Biomass of Blueberries in Alluvial Clay Soil Using Biochar and Compost

Background: The Mekong Delta features acidic clay soil of alluvial origin with a soil texture ranging from silty clay to clay. The growth of wild blueberry plants in clay soils requires the addition of materials to enhance soil porosity and aeration. Objective: The objective of this study was to examine the effects of the combined use of biochar and compost on the growth, yield, and NPK uptake of blueberry ( Vaccinium tenellum) cultivated in the Mekong Delta. Methods: The pot experiment had a 3 × 3 factorial design, containing the application of biochar at 0, 10, and 20 t ha -1 (B0, B10, and B20, respectively), compost at 0, 5, and 10 t ha -1 (C0, C5, and C10, respectively), and NPK at 45:20:20 kgha -1 according to the growth stages of blueberries. Results: The interaction between biochar and compost provided a more efficient response in terms of plant growth, yield, and NPK uptake. Notably, in the combined application of B20 and C10, NPK uptake and biomass of blueberries were significantly increased. However, only the concentration (gkg -1) of N (14.8) and K (3.82), except for P (1.37), in the blueberry leaves were below the Trevett threshold. Conclusion: This approach effectively mitigates the challenges posed by high clay content in the soil, which results in poorer soil porosity and aeration. The findings emphasize the potential benefits of tailored soil amendment strategies to optimize blueberry cultivation in similar environments.

Effect of Ultrafine Cement (UFC) on the Corrosion Resistance of Cement Soil in Peat Soil Environment.

Many peat soils are distributed around plateau lakes, and the reinforcement of peat soils with high organic matter content by ordinary cement cannot meet the actual engineering requirements. In order to obtain better mechanical properties and durability of the reinforcement, this experiment prepared peat soil by mixing humic acid reagent into the alluvial clay soil with low organic matter content. The cement soil samples were prepared by adding cement and ultrafine cement (UFC) by stirring method; the samples were then soaked in fulvic acid solution to simulate the cement soil in the peat soil environment. Using the unconfined compressive strength (UCS) test, scanning electron microscope (SEM) test, and pores and cracks analysis system (PCAS) test, the effect of UFC content change on cement soil's humic acid erosion resistance was explored, and the optimal UFC content range was sought. The results of the UCS test show that with an increase in immersion time, the strength curves of cement soil samples gradually increase to the peak strength and then decrease. Significant differences in the time correspond to the peak strength, and the overall presentation is two processes: the strength enhancement stage and the corrosion stage of the sample. The incorporation of UFC makes the cement soil in the peat soil environment exhibit excellent corrosion resistance, and the optimal UFC content is 10%. The results of the SEM and PCAS tests show that the microstructure of cement soil after immersion time exceeds 90 days, increases with an increase in immersion time, and its structural connectivity gradually weakens. The excellent characteristics of UFC particles, such as small particle size, narrow particle size distribution, fast hydration reaction rate, high hydration degree, and many hydration products, weakened the adverse effects of humic acid on the cement soil structure to a certain extent. Therefore, although the number of macropores increases, they are not connected. It still presents a relatively compact honeycomb overall structure, which correlates well with the UCS results.

ELECTROKINETIC REMEDIATION OF ARSENIC CONTAMINATION FROM ALLUVIAL AND RED CLAY SOIL

<p>In this research the arsenic contaminations issues are exposed and suitable measures are recommended through electrokinetic remediation. The arsenic expulsion was assessed using the electro kinetic remediation from two different soil tests; alluvial clay soil and red clay soil taken from the Tamilnadu zone. Three distinct cathodic electrolytes—deionized water (DIW), potassium phosphate (KH2PO4), and sodium hydroxide—were used to test the viability of upgrading experts (NaOH).The consequences of the examinations on the alluvial mud soil shows that the potassium phosphate (0.1N) was the best in extricating arsenic (79.5% removal efficiency), likely because of anion trade of arsenic species by phosphate. Then again, the sodium hydroxide (0.1N) appeared to be the most proficient in with eliminating arsenic (63%) from the red soil. The sodium hydroxide's ability to increase soil pH and hasten the ionic migration of arsenic species through the desorption of arsenic species as well as the disintegration of arsenic-bearing minerals may help to explain and suggest this result. In order to forecast the effectiveness of removing arsenic from polluted soil, studies using response surface technique are also designed using the Box Behnken Method.</p>

Artificial macropores and water management effects on reduction of greenhouse gas emissions from rice paddy fields

Rice production is an important sector of global agriculture, sustaining more than half of the world's population. However, rice production contributes significantly to global warming through increased emission of greenhouse gasses (GHGs), primarily CH4, into the atmosphere. Therefore, this study examined countermeasures to reduce GHG emissions from paddy fields without affecting rice production. A column experiment was conducted to investigate the effects of soil macroporous structure and water management on GHG emissions from flooded alluvial clay soil (paddy soil). The soils were subjected to different management regimes: with and without artificial macropores, compost, and drainage treatment. Drainage was maintained at 6.5 mm d − 1 to ensure infiltration yet prevent excessive leakage from the paddy field. The measured parameters included GHG emissions, soil water content, redox potential, soil temperature, soil swelling, total carbon, total nitrogen, iron, and manganese. The results showed that the soil column with macropores and drainage had significantly lower CO2 and CH4 emissions than that without macropores and drainage. In addition, the soil level increment, and thus, the amount of gas (CH4) produced in the soil column with drainage were lower than that without drainage. The combination of drainage treatment and macropores might have effectively acted as a hydrodynamic gradient and a structure that promotes freshwater intrusion into deeper soil profiles, inhibiting absolute anaerobic methanogenic activity. The redox potential of the column with drainage and macropores was the highest. Moreover, CO2 and CH4 emissions were reduced at a relatively small drainage rate of 6.5 mm d − 1 by adding macropores to the soil. The findings confirmed that GHG emissions were effectively reduced by a porous soil structure at a low drainage rate. Macropore application also exhibited effectiveness at mitigating nutrient loss (TOC and TN) through the drainage. Therefore, low tillage before flooding would be preferable to conserve the macroporous structure. However, the results also highlight an adverse effect on mineral leaching (particularly Mn) through the column with macropores.

EFFECT OF LATERALS DRAIN SPACING AND GROUNDWATER DEPTH ON SOIL WATER RELATIONS AND RICE PRODUCTIVITY IN THE NORTH NILE DELTA

A field experiment was conducted in alluvial clay soil located at the north Nile Delta (Motobus District, Kafr El-Shiekh Governorate, Egypt). The soil was cultivated with rice crop (Oryza sativa L.) during two summer seasons 2018 and 2019. The impact of lateral drain spacing at 20m and 40m between laterals (main plots) with controlled drainage (CD) at 0.4, 0.8m depth and uncontrolled drainage at 1.2m below soil surface (sub plots) was studied to evaluate soil-water properties, Nitrate losses, water saving, rice productivity and economic return under rice crop cultivation. Results showed that the relative groundwater depth values (RGWD) are inversely proportional to the drain spacing treatments. The highest values of drainable porosity (0.145 and 0.141%) were achieved in the plots subjected to 20 m drain spacing with uncontrolled treatment, while the lowest values ( 0.1 and 0.101%) were obtained at 40m drain spacing with 0.4m controlled drainage in both seasons, respectively. It's clear that narrow drain spacing of 20m and water table depth at 0.4m was more efficient than the wider drain spacing at 40m in reducing values of soil salinity, SAR and bulk density compared with its values before installation of drainage system. On the other, hand it gave the highest values for water saving, nitrate saving, productivity of irrigation water, rice yields, net return, net income from water unit, economic efficiency compared to wider drain spacing (40 m) with 1.2 m ground water depth. The controlled drainage reduced drainage outflow compared to conventional drainage. It can be concluded that the treatment of controlled drainage gave more profit than the uncontrolled one.

Hydraulic conductivity and sorptivity at unsaturated and saturated conditions as related to water infiltration in soils

Sorptivity (S) has been defined in terms of the horizontal infiltration equation. At unsaturated conditions (at a very short time) S represents “maximum sorption capacity”, but in saturated conditions the sorption capacity decreases with the time. Over a long time of infiltration, sorptivity was not studied as a soil water parameter that could be determined. The purpose of this study is to apply derived equations depending on the infiltration functions to predict (1) soil water sorptivity (S) at infiltration capacity ( unsaturated conditions ) and at basic infiltration rate (I b ) ( saturated conditions ), (2) the hydraulic conductivity (Saturated Ks and unsaturated K (θ ) ) into capillary-matrix and non-capillary macro pores of soils. Five alluvial (saline and non-saline clay) and calcareous soil profiles located in the Nile Delta were investigated for applying the assumed equations. A decrease in S value was observed with an increase in soil water content. At steady infiltration rate (I b ), S decreased from 1.04 to 0.647cm.min -0.5 (i.e. S decreased by 37.79%) in average in calcareous soils and from 0.537 to 0.251cm.min -0.5 (53.25%) in alluvial clay soils. The steady S w parameter was used in prediction of the hydraulic conductivities and the basic infiltration rate I b , whereas, S w is a suggested term at steady infiltration rate. The calculated values of I b were corresponding to those obtained by infiltration experiment. This confirmed the significance of steady S w as a new functional infiltration parameter. A matching factor u was calculated as a ratio between predicted I b and the measured saturated hydraulic conductivity, Ks. The mean values of u were 0.895, 0.685 and 0.360 for calcareous, clay and saline clay soils respectively. Unsaturated K (θ ) has been discriminated into saturated macro-pore K (θ ) RDP and matrix unsaturated K (θ ) h . The values of K( θ ) RDP for macro pores remained higher than those for soil matrix pores (K (θ ) h ) in the studied soils. The highest value of K (θ ) was obvious in calcareous soil profiles, while the lowest value was existed in saline clay soil. In conclusion, the predicted values of hydraulic conductivities of soil matrix (capillary) and macro (non-capillary) pores were reasonable and existed in the normal ranges of the investigated soils, indicating that the proposed equations are applicable and can be recommended to be used in coarse and fine textured soils with large scale of different properties.

The variance in growth and yield Sorghum bicolor L. Moench genotypes under different foliar nano fertilizers

A field experiment carried out in 2017 in Qurna district Al-Basra governorate in alluvial clay soil at a line of 47.27 degrees east and latitude 30.56 degrees north, with the aim of finding out the effect of foliar varieties of Nanofertilizer on the growth characteristics and yield of three varieties of the Sorghum. The results showed that the varieties differed significantly among them in most of traits, as the Alkhir variety out performed the yield components, which led to it being given the highest grain yield of 5.740 tons ha-1 and the highest protein yield of 0.608 tons. ha-1, and the results also showed the superiority of foliar with fertilizer. The nanoparticles of the both elements together are zinc and copper in the growth characteristics (161 cm, 3465 cm2) and the components of the yield (1713 grains, head-1 30.95 g), which was reflected in the grain yield, which gave the highest grain yield of 5.9 tons. ha-1 compared to the treatment of adding each element alone and the treatment of non The addition, while the significant overlap between the quality of the nanoparticle and the varieties affected some growth characteristics, grain yields and protein, as the combination (good x addition of the two elements together) gave the highest grain and protein yield, reaching 6.77 tons. ha-1 and 0.753 tons.

Genetics and ecology of plant species occurring on the Banded Iron Formations in the Yilgarn, Western Australia

Banded Iron Formations (BIFs) are a distinctive feature in the Yilgarn craton of southern Western Australia occurring as geographically isolated ranges within a mosaic of alluvial clay soils interspersed with sandplains and occasional granite outcrops. They are prominent features across a flat, highly weathered plateau, forming unique geologically stable components in an unglaciated landscape. The topographic complexity of BIFs provides areas of key environmental heterogeneity in a subdued landscape, offering a mosaic of habitats and abundance of niche microhabitats that support unique plant communities with high species diversity including many narrowly endemic species and those with distributions centred on these banded iron formations. Genetic and ecological studies have been undertaken on several species that are endemic to, or have distributions centred on, the banded iron formations of the Yilgarn. These studies provide a basis for understanding the diversity and evolutionary history of the plant communities that occur in these diverse environments. This Special Issue brings together studies on several these species to complement studies already published, and this overview provides a summary of the genetics and ecology of 21 species that are restricted to, or have distributions centred on, BIFs. Many of these species have conservation status under national and state legislation and understanding of genetics and ecology of these species assists with conservation strategies. A range of genetic patterns was identified among these species making generalisations difficult and indicating analysis of individual species is required in order to provide information for conservation and management decisions.

Persistence and stochasticity are key determinants of genetic diversity in plants associated with banded iron formation inselbergs.

The high species endemism characteristic of many of the world's terrestrial island systems provides a model for studying evolutionary patterns and processes, yet there has been no synthesis of studies to provide a systematic evaluation of terrestrial island systems in this context. The banded iron formations (BIFs) of south-western Australia are ancient terrestrial island formations occurring within a mosaic of alluvial clay soils, sandplains and occasional granite outcropping, across an old, gently undulating, highly weathered, plateau. Notably, these BIFs display exceptionally high beta plant diversity. Here, we address the determinants and consequences of genetic diversity for BIF-associated plant species through a comprehensive review of all studies on species distribution modelling, phylogenetics, phylogeography, population genetics, life-history traits and ecology. The taxa studied are predominantly narrowly endemic to individual or a few BIF ranges, but some have more regional distributions occurring both on and off BIFs. We compared genetic data for these BIF-endemic species to other localised species globally to assess whether the unique history and ancestry of BIF landscapes has driven distinct genetic responses in plants restricted to this habitat. We also assessed the influence of life-history parameters on patterns of genetic diversity. We found that BIF-endemic species display similar patterns of genetic diversity and structure to other species with localised distributions. Despite often highly restricted distributions, large effective population size or clonal reproduction appears to provide these BIF-endemic species with ecological and evolutionary resilience to environmental stochasticity. We conclude that persistence and stochasticity are key determinants of genetic diversity and its spatial structure within BIF-associated plant species, and that these are key evolutionary processes that should be considered in understanding the biogeography of inselbergs worldwide.

Impact of soil and foliar fertilization on yield and net income of maize plants alluvial clay soil.

Impact of soil and foliar fertilization on yield and net income of maize plants alluvial clay soil.

English

Two locally prevailing hetyerocystous cyanobacterial isolates, collected from alluvial clay soil and identified as Nostoc muscorum and Anabaena variabilis, were tested (either singly or mixed) for their potency to colonize the roots of wheat seedlings. N. muscorum formed close association with root hairs, whereas A. variabilis showed loose binding. The mixture of both cyanobacterial strains formed weak association with the roots of wheat seedlings. The tight colonization of N. muscorum led to accumulation of Chl "a" in the roots, as well as showed a beneficial influence on stimulating nitrogenase activity. Such tight association by N. muscorum significantly increased the growth parameters of wheat seedlings. Dry weight of the inoculated plant seedlings roots augmented by more than 3-fold of the control, wherever the shoots were promoted by more than 36% as compared to the control has no inoculation. However, the loose attachment shown by A. variabilis contributed to the weak association of the mixture of both cyanobacterial agents. Key words: Nostoc muscorum, Anabaena variabilis, Triticum variabilis, cyanobacterial isolates.

Morphogenetic features of soils in the Cat Tien National Park, southern Vietnam

Morphogenetic features of soils on the selected plots in the Cat Tien National Park in southern Vietnam have been studied with the use of a set of morphological, analytical, and instrumental methods. The lithological factor and topographic position play the leading role in the development of the particular genetic soil features. The soils can be subdivided into four groups according to these factors. The soils developing from volcanic deposits with a predominance of tephra can be classified as thin clayey brown tropical soils (Dystric Skeletic Rhodic Cambisols (Clayic)), and the soils developed from less weathered colluvial derivatives of basalts with some admixture of tephra can be classified as dark-humus clayey tropical soils (Skeletic Greyzemic Umbrisols (Clayic)). Very poor soils developed from the eluvium of argillites are classified as thin weakly developed clayey tropical soils (Dystric Regosols (Clayic)). The soils forming from the alluvial sediments of different textures are classified as alluvial loamy sandy soils (Dystric Fluvisols (Arenic, Drainic)) and as alluvial clay loamy soils (Eutric Fluvisols (Episiltic, Endoclayic)).

INTERRELATIONSHIPS OF THE SWELLING AND THE SHRINKAGE OF THE CLAY AND THE LOESSIAL SOILS

The article considers the character of the interrelationship between the relative swelling and the volumetric shrinkage of the clay and the loessial soils. The possibility of their adequacy (accordance) or antagonism (contradiction) was estimated. Examples are given from the practice of engineering surveys in Turkey (Ankara clays), Russia (eolian clays, the city of Nevinnomyssk in the North Caucasus) and the USA (forecasting the swelling of clayey soils, Oklahoma), which show the need for simultaneous study of these dangerous properties and elucidation of the factors of their manifestation. The results of experiment and investigations were presented for three objects: the proluvial loessial soils (p III–IV) of the lithological section Desyatnikov (Buryatia); the lacustrine clays (l III–IV) of the test hole 45-b (Primorye, the area of the lake Khanka); the clays of the Jurassic coal-bearing formation (engineering geological boreholes on the survey area, the microdistrict Topkinskiy, c. Irkutsk). The programs «Standard statistics» and «Cluster analysis» of the R-type microstructural parameters were determined by the method of «Microstructure», the composition of clay minerals — using X-ray diffraction analysis. The absence of interrelations between swelling and shrinkage is confirmed by the results of the experiment under conditions of a change in the moisture content of the paste samples (alluvial clay soils), the data for determining these indices for proluvial loess-like sandy loams and cohesive sands of the Desyatnikovo (Buryatiya) section and the clay of the Jurassic coal-bearing formation (Irkutsk). The manifestation of the correlation of swelling and shrinkage was established only for lake clays from the area of Fr. Khanka (Primorye), enriched with smectite. It is shown that the main factors of swelling of clayey and loess soils are the composition of clay minerals, the degree of aggregation (the number of aggregates), the actual content of the fraction < 0,002 mm, the content of primary (free) fine-fine sand (0,25–0,05 mm) particles; as well as shrinkage with the listed swelling factors, is most likely not connected, which is, apparently, the reason for the discrepancy in the manifestation of these physicochemical properties; to determine the degree of danger of the soil strata in connection with swelling or shrinkage, it is necessary to determine the value of these indicators in the course of engineering surveys in laboratory conditions on duplicate samples.

Bioremediation of chemically polluted soil cultivated with Faba bean and Maize

A greenhouse pot experiment was undertaken to ascertain the efficiency of some organic materials on decreasing the mobility of heavy metals in soil and subsequent rates of their absorption by growing plants. An alluvial clay soil was amended with each of compost, biogas manure or humic acid, at doses of 0.5 & 1.0 %C. Faba bean (Vicia faba), as a leguminous winter crop, and maize (Zea mays), as a cereal summer crop, were planted in the amended soil. A mixture of Zn+ Pb + Cu was added at the permissible safe level of each mineral and double that permissible level. Controls of no organic or mineral addition were included. Rates of Zn, Pb & Cu uptake by plants had been measured at two plant growth periods, i.e. 45& 90 days for faba bean and 30 & 60 days for maize. Total and bioavailable amounts of those minerals were also determined in the cultivated soil at termination of the experiment. The obtained results indicated that humic acid was superior as to handicap the activity of heavy metals in soil, and thus diminished their uptake by plants, greatly at the higher rate of application, and followed descendingly by biogas manure and compost; that was the case at the first detection time. However, at the later growth period, humic acid had moved back to exchange the position with compost. Capacity of plant absorption for such metals showed the order: Zn> Cu>Pb. Faba bean took up higher amounts of the assigned minerals than maize. Contents of the heavy metals in soil oppositely reflected the position revealed in the grown plants.

Rheological properties of different minerals and clay soils

Rheological properties of kaolinite, montmorillonite, ferralitic soil of the humid subtropics (Norfolk island, southwest of Oceania), alluvial clay soil of arid subtropics (Konyaprovince, Turkey) and carbonate loess loam of Russian forest-steppe zone were determined. A parallel plate rheometer MCR-302 (Anton Paar, Austria) was used in order to conduct amplitude sweep test. Rheological properties allow to assess quantitatively structural bonds and estimate structural resistance to a mechanical impact. Measurements were carried out on samples previously pounded and capillary humidified during 24 hours. In the amplitude sweep method an analyzed sample was placed between two plates. The upper plate makes oscillating motions with gradually extending amplitude. Software of the device allows to receive several rheological parameters such as elastic modulus (G’, Pa), viscosity modulus (G, Pa), linear viscoelasticity range (G’>>G”), and point of destruction of structure at which the elastic modulus becomes equal to the viscosity modulus (G’=G”- crossover). It was found out that in the elastic behavior at G '>> G strength of structural links of kaolinite, alluvial clay soil and loess loam constituted one order of 10 5 Pa. Montmorillonit had a minimum strength - 10 4 Pa and ferrallitic soil of Norfolk island [has] - a maximum one -10 6 Pa. At the same time montmorillonite and ferralitic soil were characterized by the greatest plasticity. Destruction of their structure (G '= G) took place only in the cases when strain was reaching 11-12%. Destraction of the kaolinite structure happened at 5% of deformation and of the alluvial clay soil and loess loam - at 4.5%.

Inclusion of upland crops in rice‐based rotations affects chemical properties of clay soil

AbstractIn the Mekong Delta, alluvial clay soils have been used intensively over many generations for rice monoculture. Currently, farmers are confronted by problems of declining land productivity. Rotations comprising rice and upland crops can increase soil quality, but appropriate cropping systems for paddy soils have received relatively little attention. We therefore established a multiyear field experiment to evaluate the long‐term effects of cropping systems with different rotations on soil chemical quality. Systems laid out in a randomized complete block design with four replications were as follows: (i) traditional rice monoculture with three rice crops per year (R‐R‐R), (ii) rotation with two rice crops and maize (R‐M‐R), (iii) rotation with two rice crops and mung bean (R‐Mb‐R) and (iv) rotation with one rice crop and two upland crops – mung bean and maize (R‐Mb‐M). We hypothesized that systems with rotations of upland crops and their temporary beds improve chemical quality of paddy rice soil. Soil chemical parameters were determined to better understand and evaluate the sustainability of the cropping systems. Results showed an improvement in soil chemical quality for cropping systems with rotations of rice and mung bean or maize grown on temporary beds (R‐M‐R, R‐Mb‐R and R‐Mb‐M), particularly the content of soil organic carbon and a presumed hydrolysable labile carbon fraction compared with rice monoculture. Less pronounced improvements in EC, CEC and total acidity were also found with inclusion of upland crops. Cropping systems of rice with upland crops improved rice grain and straw yield in subsequent season in contrast with rice monoculture.

Changes in the composition, texture, and properties of clay soils under the influence of microbiological denitrification and fermentation

The effect of a concentrated mixture of denitrifying and fermenting bacteria on the composition, structure, state, and properties of alluvial clay soils sampled in Perm City has been studied. The results demonstrate an increase in the volume of a sample when soaked in a solution of microorganisms, changes in the mineral composition of soils, an increase in their porosity and humidity, a decrease in the density and stress-strain characteristics. The processes of interaction between microorganisms and the components of soils are mentioned, which can lead to such effects.

Effect of Cropping System on Physical Properties of Clay Soil Under Intensive Rice Cultivation

AbstractCropping systems are thought to alter soil quality in paddy rice fields. This study was conducted to quantify the long‐term effects of continuous crop production under different cropping systems with different crop rotations on physical properties of alluvial clay soil in the Mekong Delta, Vietnam. Soil samples were collected from four treatments: (i) traditional intensive rice monoculture with three rice crops per year (R–R–R); (ii) rotation with two rice crops and maize (R–M–R); (iii) rotation with two rice crops and mung bean (R–Mb–R); and (iv) rotation with one rice and two upland crops, mung bean and maize (R–Mb–M). We hypothesized that cropping systems with rotations of upland crops and their temporary beds improve the physical quality of paddy rice soil; hence, they are better options towards sustainable agriculture. Results show an improvement of soil physical quality for systems with two rice crops and one upland crop (R–M–R and R–Mb–R) and those with one rice crop with two upland crops (R–Mb–M) compared with intensive rice monoculture (R–R–R). This was translated in decreased bulk density and soil strength, increased soil organic carbon and total porosity, and higher aggregate stability index, plant‐available water capacity, and Dexter's S index, especially at depths of 10–20 and 20–30 cm. The systems with different upland crops (maize or mung bean) showed similar high physical quality improvement. To maintain soil quality in future seasons, introducing a cropping system with at least one upland crop in rotation with rice is recommended. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Features of changing of alluvial soils of the east part of the Nile delta at anthropogenous influences

The results of researches concerning changes of properties of alluvial soils of the Nile valley are stated in work. The morphological structure, agrophysical and chemical properties of the alluvial sandy soil, alluvial loamy and meadow and alluvial clay soils of the Nile Delta are studied. It is revealed that the meadow and alluvial soils possess epy most favourable qualities. As a result of long-term meliorative and agricultural influence there was some deterioration of physical and chemical properties of alluvial soils.

Prediction of hydraulic conductivity and sorptivity in soils at steady-state infiltration

The purpose of this study was (1) to find a matching factor (u) between infiltration rate and hydraulic conductivity during steady-state infiltration, and (2) to propose equations based on infiltration and soil moisture-retention functions for prediction of the hydraulic conductivity K(θ) within the rapidly (non-capillary) drainable pores (RDP) and capillary-matrix pores of soils. The K(θ) of capillary pores was divided into K(θ)SDP, K(θ)WHP and K(θ)FCP within slowly drainable pores (SDP), water-holding pores (WHP) and fine capillary pores (FCP), respectively. Five soil profiles of calcareous sandy loam, alluvial saline and non-saline clay, located at the Nile Delta, were used to apply the proposed equations. The highest and the lowest values of K(θ)RDP were observed in calcareous and saline clay soil profiles, respectively. Values of K(θ)RDP remained higher than those for capillary pores in the studied soils. The predicted values of K(θ) in capillary and non-capillary pores classes were in the expected range for unsaturated hydraulic conductivity. Water sorptivity (S) was determined at initial unsaturated soil water conditions and calculated at steady-state infiltration (S w) using a derived equation. There was a decrease in S with an increase in soil water content; i.e. at steady-state infiltration, S decreased by 35–40% in calcareous soils and by 45–60% in alluvial clay soils. The parameter values of u and S w tended to be uniform in calcareous soils, but nonuniform in saline and non-saline clay soils.