Validation of Flash Flood Simulations Using Satellite Images and Community-Based Observations—Impact of Infiltration and Small-Scale Topographical Features

This work is aimed at investigating flash floods in the region of El Gouna, Egypt, by using a 2D robust shallow-water model that incorporates the Green-Ampt model to find the most realistic infiltration setting for this desert area. The results of different infiltration settings are compared to inundation areas observed from LANDSAT 8 images as well as to community-based information and photographs to validate the results despite scarce data availability. The model tends to overestimate infiltration in the study area if tabulated Green-Ampt parameters for the dominant soil texture class are considered. Specifically, bare soils with no vegetation tend to develop a surface crust, leading to significantly decreased infiltration rates during heavy rainfalls. Comparing the results of different infiltration settings with the observed data showed that the crust approach or the consideration of sandy clay loam instead of sand led to more plausible results for the considered study area than those obtained using the values for sand from two different sources in the literature. Furthermore, small-scale structures, which are not appropriately captured in the original digital surface model, but significantly affect the resulting flow field, have been included based on the available information leading to much more plausible results.

Soil Erodibility in European Mountain Beech Forests

Forests in Europe are, at present not endangered by soil erosion, however, this can change with climate change or intensified forest management practices. Using a newly established network of plots in beech forests across Europe, the aims of this study were 1) discrimination of soil properties and erodibility indices in relation to bedrock, 2) determination of geochemical properties and Corg influencing erodibility, and 3) assessment of the effect of soil depth on erodibility indices. Seventy-six soil samples from 20 beech forests were collected in 11 countries to quantify soil properties influencing erodibility indices clay ratio, modified clay ratio, sodium adsorption ratio, and oxides ratio. Results indicate that dominant soil properties, determined by bedrock, that correlate with forest soil erodibility indices are: Corg, pH, EC, Ca and Na ion concentrations, total-water soluble cations, and the % of sand. According to the tested indices, soil susceptibility to erosion follows the sequence: granite>andesite>sandstone>quartzite>limestone. Deeper soil horizons on granite are more susceptible to erosion than surface horizons, while this is not the case for soils on limestones. In conclusion, forest management should consider the predisposition of different soil types to erosion.

Comparison of Soil Biological Properties and Bacterial Diversity in Sugarcane, Soybean, Mung Bean and Peanut Intercropping Systems

Sugarcane intercropping with soybean [Glycine max (Linn.) Merr.], mung bean [Vigna radiata (Linn.) Wilczek] and peanut (Arachis hypogaea Linn.) as well as a sugarcane monoculture were conducted to study the impacts of intercropping on soil biological characteristics and bacterial diversity. The results showed that soil cultivable microorganisms, the activities of soil enzymes and microbial biomass carbon, nitrogen, and phosphorus were all significantly improved by intercropping with soybean and mung bean. Additionally, soil bacterial diversity and richness in sugarcane fields were also significantly enhanced by intercropping with soybean and mung bean. In addition, soil bacterial community structures in sugarcane fields can be altered by intercropping with different legumes. Proteobacteria, a high-nutrient-tolerant bacterial assemblage, became the dominant bacteria in the sugarcane-soybean and sugarcane-mung bean intercropped soils. Twenty four, 28, 26 and 27 dominant soil bacterial genera were found after the sugarcane-soybean, sugarcane-mung bean, sugarcane-peanut and sugarcane monoculture treatments, respectively. Sugarcane-mung bean intercropping being the most promising system for regaining and improving soil fertility and soil heath and facilitate agriculture intensification of sugarcane.

Soil fertility and leaf nutrient status of litchi orchard sites

Twelve soil and twelve leaf samples were collected from twelve litchi (Litchi chinensis Sonn.) orchards from different locations of Dinajpur to evaluate some physico-chemical properties and nutrient status of soil, and concentration of nutrients in litchi leaf. The pH of the soil varied from very strong acidic to medium acidic (4.8 - 5.7), organic matter content varied from 0.84 - 1.88%, EC varied from 302.4 - 310.2 μS/cm. The dominant soil textural class was clay loam. The average particle density was 2.49g/cm3. Total N, P, K and S in soils were 0.053 - 0.180%, 0.02 - 0.07%, 0.046 - 0.370 meq/100 g, and 0.015 - 0.028%, respectively. Available N, P, K, S, Zn, Fe, Mn and B in soils 30.40 - 57.8 mg/kg, 10.53 - 14.33 mg/kg, 0.03 - 0.32 meq/100 g, 20.03-34.80 mg/kg, 0.68-1.50 μg/g, 31.8 - 41.5 μg/g, 6.75 - 7.39 μg/g and 0.25-0.51 μg/g, respectively. The concentration of total N, P, K, S, Zn and Mn in the leaf were 1.74 - 2.20%, 0.11 - 0.188%, 0.104- 0.198%, 0.129 - 0.430%, 12 - 14 μg/g and 30 - 74 μg/g, respectively. The overall results indicated that the fertility status of the soils under the litchi plantation in the Dinajpur area are medium fertile. So, farmers could be advised to grow litchi plants after applying amendments to the soils to improve the physico-chemical properties in the Dinajpur area of Bangladesh. Dhaka Univ. J. Biol. Sci. 30(2): 141-149, 2021 (July)

Evaluation of the Sulphur-Supplying Ability of Soils to Support Plant Growth and Assessment of Relative Crop Response to Sulphur Application through Neubauer Technique

Sulphur plays a vital role in the nutrition of oilseeds and pulses. Along with nitrogen and phosphorus, it plays an important role in the formation of proteins and is involved in the metabolic and enzymatic processes of all living cells. Several biological techniques have been studied in order to assess sulphur deficiency or sufficiency in different groups of sulphur fertilizer for achieving the optimum yield of crops of which Neubauer technique is generally considered as one such tool that can be used for piloting the sulphur supplying capacity of the soils to supplement its requirement for the establishment of the plant. Surface (0-15 cm) soil samples from typical rice and pulse growing fields spread over the dominant soil groups of West Bengal which belong under 16 identified soil series were collected for this study. In order to assess sulphur availability in soils Neubauer technique was employed. Under sulphur treatment, the lowest dry matter yield and uptake by shoot was recorded in Bankul soil. Among the soils, the lowest root dry matter yield at control treatment was recorded in patapahari soil and the highest was in Hijalgara soil. A similar trend was also observed in case of S uptake by the shoot. While highest dry matter yield and maximum sulphur uptake by shoot was registered in Sukhnibasa and kusmi soil respectively. Likewise for N, P and K elements, the Neubauer technique may be used as one of the biological techniques for evaluating S response to crops as well as S supplying capacity of the soil to support plant growth.

The Influence of Drying-Wetting Cycles on the Suction Stress of Compacted Loess and the Associated Microscopic Mechanism

To better understand and analyze the unsaturated stability of loess filling body, it is necessary to study the changes in suction stress before and after the drying-wetting cycles. In this study, the SWCC of compacted loess before and after drying-wetting cycles was tested using the filter paper method. Then, the suction stress was calculated and the microstructure of the loess sample was determined by the SEM and NMR. The results showed that the drying-wetting cycles had an important influence on the SSCC and microstructure of compacted loess. The change in suction stress before and after the drying-wetting cycles can be well explained by the loess microstructure. The drying-wetting cycles did not significantly change the basic trend of the compacted loess’s SSCC, but it increased the porosity and the dominant pore diameter of loess, and reduced the suction stress under the same matric suction. The main significant change in suction stress with matric suction occurred within the range of the dominant soil pores. The larger the dominant pore diameter, the smaller the suction stress under the same matric suction. In addition, this study proposes a new method for calculating suction stress based on the PSD parameters.

SPATIAL DISTRIBUTION OF THE WESTERN JADWAL SOILS PROPERTIES AND SUITABILITY EVALUATION FOR WHEAT CROP CULTIVATION BY GEOMATICS TECHNOLOGY

The study area was chosen in the district of the western Jadwal in Karbala governorate - Iraq, which is located between E44o05'10'' to E44o13'03'' and N32o38'30'' to N32o27'40'', as 100 locations were identified for the depth of 0-30 cm by auger hole sampling method samples were obtained from each site, and kept laboratory measurements. The results of the study showed that the dominant soil texture is medium clay and silt are the predominant separates in the soil. As for the salinity of the soil represented by electrical conductivity, it was low of the dissolution the salts and the land use for cultivation besides the presence of a drainage network a percentage of the organic matter is good. As for assessing the suitability of the land for cultivation, Results showed the use of the standard addition method of land evaluation for the wheat crop by Sys,1993 is better and more accurate than the standard multiplication method for the wheat crop that was also suggested by Sys, 1980, where the very suitable class S1 and the suitable S2 were the predominant cultivars of the addition method, while the non- suitable class N and the least suitable S5 were classes when the methods of multiplication were used.

INTERACTION OF SOIL ORDERS AND LEVELS OF APPLIED PHOSPHORUS ON P-STATUS OF SOIL CALTIVATED WITH WHEAT AT ELONGATION STAGE

A pot experiment was carried out during autumn growing season of 2016-2017 at the Gerdarasha field of College of Agriculture Engineering Sciences, to study the effect of three dominant soil orders (Mollisols (M), Vertisols (V) and Aridisols (A)), five levelsof applied triple super phosphate (TSP) fertilizer (0, 80, 160, 240 and 320 kg TSP ha-1) and combination between them on chemical availability of phosphorus (P) using solubility diagram at elongation stage and wheat yield. The factorial experiment was depended using a completely randomized design (CRD) with three replicates. The results indicated that the soil orders were affected on phosphorus status, it has appeared that the studied soil order was located between TCP and HA for both Aridisols and Vertisols it means the solubility of phosphorus is low. but in Mollisols is slightly more than Vertisols and Aridisols. It is the P-status and availability was very low since shifting towards TCP, it means precipitation of P in a non-available form then decrease in its availability. The application of phosphorus fertilizers caused shifting the points towards a more soluble form of phosphorus. The results indicated that the application of TSP fertilizer increased the solubility of P in the studied dominate soil orders. Then, the treatment combination (M, V, A) TSP0 were the nearest point to TCP falling between TCP and OCP which were the lowest soluble of phosphorus there less available, phosphorus application of phosphorus caused to shifting towards DCP In contrast, for treatment combination (M,V and A) TSP320 kg ha-1 were located between OCP and DCP the nearest point treatment combination for DCP

The Influence of Drying-Wetting Cycles on the Suction Stress of Compacted Loess and the associated Microscopic Mechanism

In order to better understand and analyze the unsaturated stability of loess fillings, it is necessary to study the changes in suction stress before and after the drying-wetting cycles. In this study, the soil-water characteristic curve (SWCC) of compacted loess before and after drying-wetting cycles was tested using the filter paper method. Then, the suction stress was calculated and the microstructure of the loess sample was determined by the scanning electron microscope（SEM）and nuclear magnetic resonance (NMR). The results showed that the drying-wetting cycles had an important influence on the suction stress characteristic curve (SSCC) and microstructure of compacted loess. The change in suction stress before and after the drying-wetting cycles can be explained by the loess microstructure. The drying-wetting cycles did not significantly change the basic trend of the compacted loess's suction stress, but it increased the porosity and the diameter of the dominant pore (i.e., the inter-aggregate pore) of the sample, and reduced the suction stress when the same matrix suction was applied. The main significant change in suction stress with matrix suction occurred within the range of the dominant soil pores. The larger the diameter of the dominant pore, the smaller the suction stress under the same matrix suction. In addition, this study also proposes a new method for calculating suction stress based on the pore size distribution（PSD） parameters, which is more convenient than traditional calculation methods based on SWCC parameters.