Increased Soil Resistance Research Articles

Screening of Active Oil Destructors from Various Zones of Urban Soils (on the Example of Baku)

Active cultures of hydrocarbon-decomposing microorganisms from soils of various functional zones of Baku were screened. It was shown that 15 cultures of hydrocarbon-decomposing microorganisms isolated as a result of continuous screening belonged to the genera Rhodococcus, Pseudomonas, Bacillus, Mycobacterium, Actinomyces, Arthrobacter, Micrococcus and were able to use various hydrocarbons (crude oil, paraffin and aromatic hydrocarbons and petroleum products) as the only source of carbon and energy. According to the degree of decomposition, petroleum hydrocarbons were ranked in the series: a mixture of paraffins petroleum products aromatic hydrocarbons crude oil, while the most active strains of microorganisms were isolated from the soils of the industrial and transport zones of Baku, compared with the soils of the recreational zone. The isolated active strains can be considered promising for the creation of biological products to increase soil resistance to pollutants and activate the processes of self-purification of already contaminated soils.

Effects of tree and shrub species on soil quality, sediment detachment capacity caused by rills and surface slope stability in forest lands of Northern Iran

A root system is an important factor to increase soil resistance to detachment of soil particles. However, due to the large number of species, there is a need for studying the impacts of native plant species on soil quality and soil erodibility. This investigation did flume experiments at various soil slopes (9.2%, 18.1%, 25.1%, and 32.5%) and different water flow rates (0.56, 0.67, 0.74, 0.81, and 0.94 L/(m·s)), to evaluate sediment detachment capacity caused by rills (Dc) and rill erodibility (Kr) as well as the soil quality of hillslopes with three common species including Carpinus betulus (as a natural tree species), Alnus glutinosa (as a planted tree species) and Mespilus germanica (as a shrub species) in forestland of northern Iran. The variability of Dc has been associated with soil properties and root characteristics of Carpinus betulus. Dc was significantly lower (average, −45%) for soils under Carpinus betulus compared to soils with the two other plant species (p < 0.01). This was due to the higher values of soil properties including medium weight diameter of soil aggregates (MWD), organic carbon (OC), total nitrogen (TN), total phosphorous (TP), potassium (K), calcium (Ca), magnesium (Mg) as well as to the more extended root system, as confirmed by the negative correlations between Dc and the studied variables. Kr also was different among the studied soils and plant species. The root system of Carpinus betulus also played a useful role for increasing soil resistance to rill erosion yielding a safety factor (1.61) in the studied forest ecosystem. Overall, the current study supports a broader use of native species (such as Carpinus betulus) in areas exposed to surface erosion and instability, as an effective eco-engineering conservation technique and an alternative technology instead of utilizing artificial and expensive management practices.

Simulation of soil cutting blade wear

The results of a laboratory study of the wear patterns of blades of tillage parts are presented. To substantiate the model of soil-cutting blade wear in laboratory studies. Applied installation, providing rectilinear movement of the sample, one-time interaction of the blade with the particles of abrasive mass, and reproducing chip separation, inherent in most loamy soils. The dependence of the angle of inclination of the occipital chamfer to the bottom of the furrow, the width of the occipital chamfer and blade wear along the length of the sample from the cutting path, taken in studies for the main parameters of wear, were obtained. It was found that with increasing depth of cut, the intensity of wear increases, but when there are irregularities and undulations of the bottom of the furrow, it decreases due to the increase in the cutting path with lower loads due to the alternation of depressions and protrusions at the bottom of the furrow. With increasing hardness of the abrasive mass, the intensity of wear of the blade increases, at the same time the value of the stabilized angle of the occipital chamfer to the bottom of the furrow decreases, due to changes in the wear mechanism. With increasing cutting speed, the intensity of blade wear increases due to increased soil resistance forces and specifi c energy expended on its deformation and destruction. It was shown that the abrasive model of the soil corresponds to the real loamy soil for the study of wear of cutting elements. The expansion of the characteristics of the soil model peculiar to "nature" is due to the inclusion of additional components, in particular ceresin and vaseline, in the composition of the base "paraffin + quartz particles".

Water Hyacinth Biochar: A Sustainable Approach for Enhancing Soil Resistance to Acidification Stress and Nutrient Dynamics in an Acidic Nitisol of the Northwest Highlands of Ethiopia

Soil acidity impacted over 43% of Ethiopia’s arable land and debilitated agricultural productivity. Due to reacidification susceptibility, high costs, and inadequate availability of lime, biochar has emerged as an alternative soil acidity ameliorator. However, biochar application, particularly from invasive plants such as water hyacinth, as a soil acidity amendment and waste management strategy has not fully expanded in Ethiopia. Therefore, this study investigated the potential of water hyacinth biochar (WHB) to enhance soil resistance to acidification stresses and nutrient dynamics in an acidic Nitisol of the northwest highlands of Ethiopia. An incubation study was conducted using nine treatments viz. control (soil only), biochar produced using a furnace (WHBf), and a grounding method (WHBg) each at 1% and 2% application rates, lime (L), fertilizer (F), 2% WHBf combined with fertilizer (2WHBfF), and lime combined with fertilizer (LF). Soil samples, except the control, underwent simulated acidification with HNO3. The results showed that WHB decelerated nitrification, reduced H+ ions released into the soil, and enhanced available phosphorus and nitrogen dynamics. After incubation, 1% and 2% WHB applications increased soil pH in the range of 0.30–0.35 and 0.72–0.86 units, respectively, compared to the limed soil. Conversely, exchangeable acidity decreased by 26.5% to 28.8% and 58.4% to 63%, respectively. The 2WHBfF treatment led to soil pH increases of 0.71 and 0.90 units, with exchangeable acidity reductions of 49.8% and 64.7% compared to the LF and F treatments, respectively. Compared to lime, WHB treatments demonstrated more effective resistance against soil acidification from nitrification and simulated acidification with HNO3. Therefore, WHB can be used as a sustainable approach to increase soil resistance against various acidification stresses while aiding in soil nutrient management. The study’s findings can offer valuable insights to change environmental challenges into sustainable soil acidity management approaches.

CURRENT TRENDS IN THE DEVELOPMENT OF AGRICULTURAL SYSTEMS IN THE UDMURT REPUBLIC

Minimisation of soil tillage is one of the defining trends in the development of agriculture. It allows for a significant reduction in agrotechnical operations in crop cultivation, thereby reducing the technological load on soils, energy, and labour inputs in production and increasing soil resistance to erosion processes. Minimum tillage effectively promotes the restoration of potential and adequate soil fertility and aligns with the principles of adaptive landscape agriculture. Despite numerous positive aspects of minimum tillage, its implementation in production is restrained by certain drawbacks: worsening of crop phytosanitary conditions, increased plough layer density, differentiation of the plough layer by agrochemical and agrophysical indicators, and more. To assess the possibility of implementing minimum tillage in the soil and climatic conditions of the Udmurt Republic, long-term field experiments have been conducted at the Udmurt Research Institute of Agriculture since 1980. Both positive and negative aspects of three types of primary soil tillage have been identified. Moldboard ploughing, throughout the observation period, compared to other types of tillage, provided the highest crop yield (by 0.15 0.50 t per hectare or 5.6 17.5%) and energy efficiency coefficient (by 1.9 16.7%). No-till soil treatment proved to be the most environmentally friendly, increasing the organic matter content in the 0-10 cm layer by 8.1 11.5%. However, it led to a strong differentiation of the plough layer into two sub-layers: 0-10 and 10-20 cm. The lower sub-layer was characterised by higher density and lower content of mineral nutrients and humus. In most cases, combined tillage showed intermediate results. Further scientific research is needed to develop agrotechnologies with more significant minimisation of soil tillage.

Cultivar-dependent differences in tuber growth cause increased soil resistance in potato fields.

Since soil compaction of potato fields delays shoot emergence and decreases total yield, the causes and effects of this compaction need to be better understood. In a controlled environment trial with young (before tuber initiation) plants, roots of cv. Inca Bella (a phureja group cultivar) were more sensitive to increased soil resistance (3.0 MPa) than cv. Maris Piper (a tuberosum group cultivar). Such variation was hypothesized to cause yield differences in two field trials, in which compaction treatments were applied after tuber planting. Trial 1 increased initial soil resistance from 0.15 MPa to 0.3 MPa. By the end of the growing season, soil resistance increased three-fold in the upper 20cm of the soil, but resistance in Maris Piper plots was up to twice that of Inca Bella plots. Maris Piper yield was 60% higher than Inca Bella and independent of soil compaction treatment, whilst compacted soil reduced Inca Bella yield by 30%. Trial 2 increased initial soil resistance from 0.2 MPa to 1.0 MPa. Soil resistance in the compacted treatments increased to similar, cultivar-dependent resistances as trial 1. Maris Piper yield was 12% higher than Inca Bella, but cultivar variation in yield response to compacted soil did not occur. Soil water content, root growth and tuber growth were measured to determine whether these factors could explain cultivar differences in soil resistance. Soil water content was similar between cultivars, thus did not cause soil resistance to vary between cultivars. Root density was insufficient to cause observed increases soil resistance. Finally, differences in soil resistance between cultivars became significant during tuber initiation, and became more pronounced until harvest. Increased tuber biomass volume (yield) of Maris Piper increased estimated mean soil density (and thus soil resistance) more than Inca Bella. This increase seems to depend on initial compaction, as soil resistance did not significantly increase in uncompacted soil. While increased soil resistance caused cultivar-dependent restriction of root density of young plants that was consistent with cultivar variation in yield, tuber growth likely caused cultivar-dependent increases in soil resistance in field trials, which may have further limited Inca Bella yield.

The Effects of Particle Size Distribution and Moisture Variation on Mechanical Strength of Biopolymer-Treated Soil

Biopolymers have recently shown great potential to replace traditional binding materials in geotechnical engineering; however, more research is required to reach a deeper understanding of biopolymer-treated soil behavior. The objective of this study was to investigate the most important parameters that affect the behavior of biopolymer-treated soil, including biopolymer content, dehydration time, soil type effect, and durability. Sodium alginate and agar biopolymers were used due to their stability under severe conditions and the reasonable costs to study these parameters. A broad range of soil particle sizes was used to optimize the kaolinite-sand combination. As one of the main concerns in the behavior of biotreated soils, durability was investigated under five cycles of wetting and drying. In addition, a comprehensive microstructural study was performed by FTIR analysis and SEM images, as well as chemical interaction analysis. The results indicated that the optimized biopolymer content was in the range of 0.5-1% (to soil weight) and the dehydration time was 14 days. A soil combination of 25% kaolinite and 75% sand provided the highest compressive strength. Under wetting and drying conditions, biopolymers significantly increased soil resistance against strength reduction and soil mass loss. This study provides an understanding how agar and sodium alginate changes the behavior of the soil and can be used as a reference for further studies in the future.

COMPARATIVE ASSESSMENT OF AGROPHYSICAL PROPERTIES UNDER DIFFERENT TECHNOLOGIES OF SOIL PROCESSING IN CROP ROTATION

World and domestic experience in the use of technologies has led to the need to revise approaches to soil cultivation, directions are primarily concerned with its minimization. The purpose of the research is to compare and substantiate the impact of different tillage technologies in a three-field crop rotation on the physical properties of typical chernozem. Applied materials and methods research results in a field experiment, analysis, generalization and statistical processing of data from stock and modern literary materials. The results of the study of the application of soil tillage technologies on the density and hardness of the soil, the productivity of soybeans of the central forest-steppe of Ukraine are presented. It was established that the density of the soil under "No-till" technology and minimal tillage leads to an increase in the density of the soil compared to plowing. Its increase occurred most in the 20-30 cm layer of typical chernozem with minimal tillage. Replacing the shelf with zero and minimal tillage increased soil resistance. The hardness in the soil laver 0-30 cm after disk tillage was higher than plowing by 5.5 kg/cm2, after "No-till" technology – by 8.2 kg/cm2. Soybean productivity with soil discing decreased by 5.4% compared to plowing. According to the "No-till" technology and plowing the yield of soybean grain was obtained at the same level, which is 2,19 and t/ha, respectively. A promising direction for further research is the study of the structural and aggregate composition and reserves of available moisture in the meter-thick soil laver.

ЗАВИСИМОСТЬ СТРУКТУРНО-ФУНКЦИОНАЛЬНЫХ СВОЙСТВ ПОЧВЫ ОТ ЕЕ ОБРАБОТКИ ПРИ ВОЗДЕЛЫВАНИИ ГОРЧИЦЫ

The article presents the results of studies on the study of the influence of various tillage systems on the bulk density, structural aggregate composition and water resistance of the arable layer under mustard crops. The studies were carried out in 2019-2021 in Ulyanovsk region. Five tillage systems were studied: 1. Moldboard - (plowing at 20-22 cm PLN-4-35) control; 2. Differentiated different-depth - (alternating plowing by 25-27 cm PLN-4-35 and disking by 6-8 cm); 3. Comb-shaped (OP-3C for 13-15cm); 4. Disc - (BDM for 6-8cm); 5. Flat-cut processing - (KPSh-3 by 13-15 cm). The soil of the experimental plot is represented by slightly leached heavy loam}- chernozem with a humus content of 5.8-6.1%. The dependence of some agrophysical properties of leached chernozem on reducing the intensity of influence on the treated layer is determined. Replacing plowing with non-moldboard loosening (options with comb, disc and flat-cut cultivation) or its periodic use against the background of disc cultivation in crop rotation (variant with differentiated cultivation) had a positive effect on the soil structure, increasing not only the structural coefficient, but also the water resistance of the aggregates, contributing to increasing soil resistance to water erosion. It was found that in these options, the content of agronomically valuable structural and water-resistant aggregates increased by 1.4-2.3 and 0.8-1.7% compared to traditional plowing, the structural coefficient increased by 0.29-0.49 units The lowest density of the soil structure at a depth of 0-30 cm was noted in the variant with differentiated tillage of 1.07 g cm3. On non-arable variants, the density of soil composition increased by 0.04-0.16 g/cm3 or 3-14%, compared with the control, but did not go beyond the optimal. According to the reserves of productive moisture in the meter layer of soil, differentiated and comb-shaped treatments were not inferior to the control

Research on Lightning Overvoltage of Oil-Gas Pipeline Caused by Lightning Strikes on Adjacent Electrical Transmission Line

As natural lightning strikes on a transmission tower, lightning current will flow along grounding lines into the adjacent tower grounding grid. As lightning current is dispersed from the tower grounding grid into the soil, a lightning overvoltage may be produced on adjacent pipelines. In this paper, the lightning current shunt characteristics in multi-tower scenarios are calculated by simulation method under different soil resistivity conditions. Then, based on the lightning current shunt characteristics, the current dispersion process among multi-tower grounding grids and the pipeline is analyzed with different soil resistivities, gap distances, and lightning current amplitudes. Finally, the protective effect of “drain wire” and “forced commutation” on pipeline overvoltage are compared. Simulation results showed that with increasing soil resistivity, tower grounding resistance was increased and tower shunt coefficient decreased. Considering lightning current through the multi-tower grounding grids, pipeline overvoltage is much larger than that of a single tower. Pipeline overvoltage is increased with soil resistivity and lightning current amplitude, while it is decreased with “pipeline-line” distance. Both “drain wire” method and “forced commutation” method can effectively reduce pipeline potential.

Soil reinforcement potential of cultivated cardoon (Cynara cardunculus L.): First data of root tensile strength and density

Plant roots play a key role in erosion control by increasing soil resistance to shear stress. Root tensile strength data have been published for natural systems, less is available on cultivated crops. Cardoon (Cynara cardunculus L.) is raising a growing interest as multipurpose crop for marginal lands. In this work we measured cardoon roots tensile strength, topsoil root area ratio, root length density and estimated soil reinforcement potential. Root samples were collected in late spring and at the beginning of fall and were subjected to tensile strength tests in laboratory. Tensile strength (σmax) ranged between 1.57 and 254.78 MPa, decreasing with by a power-law relationship with high determination coefficients (>0.75), with differences between summer and fall roots. We measured root length density (RLD) and root area ratio (RAR) in surface soil (top 5 cm) at different positions in the row and inter-row. RAR was used to calculate soil reinforcement potential (Cr = 1.2 * ∑σmax (kPa) * RAR (cm2 cm−2)). Average RLD was quite high 8.68 cm cm−3 with a mean value of 9.183 cm cm−3 on the row and 8.179 cm cm−3 on the inter-row, though differences between row and inter-row, were not significant. RAR was on average 0.017 cm2 cm−2. Average soil reinforcement was 194 kPa with values ranging from 67.34 kPa to 265 kPa. This is not to be interpreted as absolute reinforcement values, due to drawbacks of the simple model used, but they are useful for comparisons within the framework of crop choices. Cardoon produces a dense mat of fine roots that can contribute to increase soil cohesion, thus providing important ecosystem services.

Effect of Adsorbents on Resistance Parameters of Heavy Metal-contaminated Clayey Sand Soils

Combining soil with some adsorbents improves soil structure and shear strength. Thus, an optimal ratio of some adsorbents in the soil composition enhances soil adsorption capacity, reduces the possibility of groundwater contamination with these hazardous compounds, and leads to increase soil resistance parameters. This paper investigates the effect of heavy metals and adsorbents on the geotechnical behavior of clayey sand soils contaminated with lead and zinc as heavy metals as well as zeolite and rice husk ash as adsorbents. Clayey sand (mixture of sand with 20% kaolinite or bentonite) was considered as a base composition and the behavior of it was studied in both contaminated and uncontaminated states. Then, for increasing the heavy metal adsorption capacity of clayey sand, two types of adsorbents (zeolite and rice husk ash ) were added to the base composition and their behavior were investigated in the case of Lead and Zinc contamination. The results revealed that replacing the rice husk ash and zeolite adsorbents in the sand combination with 20% kaolinite clay significantly reduced the concentration of lead and zinc nitrate in the solution. Replacing 15% of rice husk ash with kaolinite heightened the absorption of lead nitrate and zinc nitrate by 228.8% and 291.6% in kaolinite sand. It was also found that adding nitrate to kaolinite increased the liquid and plastic limits. According to the results, in kaolinite, the value of the liquid limit rose from 49.8 to 59.1 upon elevating the concentration of lead to 5000 ppm, while the plastic limit also increased from 31 in the non-contaminated state to 36.4 in 5000 ppm in the infected state. According to obtained results, the dispersed structure is formed by increasing the concentration of lead nitrate in composition of sandy clay with low plasticity adsorbent; thus, shear resistance decreased. Changing in type of clay minerals to high plasticity cause the different trend in shear resistance parameters. Increasing the concentration of lead nitrate in bentonite composition, lead to flocculated structure be formed and shear strength increased.

Do roots bind soil? Comparing the physical and biological role of plant roots in fluvial streambank erosion: A mini-JET study

The roots of riparian vegetation can reduce fluvial streambank erosion by increasing soil resistance to erosion or by altering the applied hydrodynamic force of flowing water; however, the relative importance of these mechanisms is unknown. To assess the physical and biological effects of plant roots on streambank fluvial erosion, laboratory-scale testing was conducted using a mini Jet Erosion Testing (JET) device. Data analysis was conducted on three treatment groupings: (1) no roots (NR, n = 24); (2) synthetic roots (SR, n = 24); and (3) live roots (LR, switchgrass [Panicum virgatum], n = 12). Soil erosion was quantified by measuring the final volume of soil loss and calculating critical shear stress (τc) and the soil erodibility coefficient (kd). Potential explanatory soil and root properties, including percent water stable aggregates, root length density, and extracellular polymeric substances, were also measured. Kd was lower in rooted soil samples compared to NR when root length density was 2 cm cm−3 or higher, indicating that soil with densely packed fibers (either live and synthetic) have an impact on the applied hydrodynamic forces. However, τc was significantly higher in LR compared to both NR and SR, suggesting that only living roots provide additional soil protection by increasing soil resistance to fluvial erosion. The results of this study further emphasize that plant roots protect streambank soils from fluvial erosion through multiple mechanisms; nevertheless, further research is needed to determine which mechanism(s) plays a dominant role.

Simulation of soil cutting blade wear

The results of a laboratory study of the wear patterns of blades of tillage parts are presented. To substantiate the model of soil-cutting blade wear in laboratory studies. Applied installation, providing rectilinear movement of the sample, one-time interaction of the blade with the particles of abrasive mass, and reproducing chip separation, inherent in most loamy soils. The dependence of the angle of inclination of the occipital chamfer to the bottom of the furrow, the width of the occipital chamfer and blade wear along the length of the sample from the cutting path, taken in studies for the main parameters of wear, were obtained. It was found that with increasing depth of cut, the intensity of wear increases, but when there are irregularities and undulations of the bottom of the furrow, it decreases due to the increase in the cutting path with lower loads due to the alternation of depressions and protrusions at the bottom of the furrow. With increasing hardness of the abrasive mass, the intensity of wear of the blade increases, at the same time the value of the stabilized angle of the occipital chamfer to the bottom of the furrow decreases, due to changes in the wear mechanism. With increasing cutting speed, the intensity of blade wear increases due to increased soil resistance forces and specific energy expended on its deformation and destruction. It was shown that the abrasive model of the soil corresponds to the real loamy soil for the study of wear of cutting elements. The expansion of the characteristics of the soil model peculiar to «nature» is due to the inclusion of additional components, in particular ceresin and vaseline, in the composition of the base "paraffin + quartz particles".

Impacts of near soil surface factors on soil detachment process in benggang alluvial fans

Soil detachment processes are greatly impacted by vegetation recovery. However, the understanding of these relationships on bengggang alluvial fans in southeast China is limited. In this research, the impacts of near soil surface factors (litter stems, biological crusts, and roots) on soil detachment is quantitated by overland flow with two introduced grass species (Paspalum mandiocanum and Pennisetum giganteum) in the alluvial fans. Flow scouring was performed on soil samples obtained from two grasslands under nine forms of shear stress ranging from 2.70 to 10.51 Pa. Paspalum mandiocanum and Pennisetum giganteum significantly reduced the soil detachment capacity of alluvial fans by 94% and 98%, respectively. The roots of the two kinds of grass were most effective in reducing soil detachment (48% and 63%), the situation of >80% was caused by root binding; besides, the contribution of biological crusts (37% and 20%) was higher than that of litter-stems (9% and 15%). Compared with bare land, roots and biological crusts under Paspalum mandiocanum and Pennisetum giganteum decreased rill erodibility by 43% and 40%, 60% and 20%, respectively; meanwhile, they increased the critical shear stress by 0.92- to 3.02-fold, 1.15- to 3.34-fold, respectively. Roots of the two plants increased soil resistance more than the biological crusts mainly by root binding. Overall, Pennisetum giganteum (a deep roots plant) showed a slightly better performance in controlling soil detachment than Paspalum mandiocanum (a shallow roots plant); among them, the roles of roots and litter-stems of Pennisetum giganteum were greater than those of Paspalum mandiocanum while the role of biological crusts of Paspalum mandiocanum was greater than that of Pennisetum giganteum. These findings highlight the significance of litter-stems, biological crusts and roots in controlling soil erosion and are helpful for selecting suitable grasses for vegetation recovery in alluvial fans of benggang.

Cathodic protection design optimization of a buried vessel by FEM simulation

AbstractInstalling linear anode loops around a buried vessel is one of the latest cathodic protection anode arrangements for buried vessels. In this arrangement, besides the physical properties of the environment, for example, soil resistivity and oxygen content, the distance of anode loops to the vessel, number of anode loops, and distance between each loop are three main designing parameters. In the present study, the cathodic protection of a buried vessel (8‐m long; 2.5 m in diameter) with complete nonlinear polarization at the protected surface is studied with finite element method simulation. The analyzed variables are the number of anode loops from one to three, the anode‐to‐vessel distance from 0.2 to 0.6 m, the distance between loops from 0.2 to 1.6 m. Soil resistivity varies from 10 to 500 Ω·m, and oxygen limiting current density changes from 5 to 100 mA/m2. Increasing anode‐to‐vessel distances will reduce the potential differences, and the best condition is the maximum distance, 0.6 m. The optimum number of anode loops is two. Increasing soil resistivity will increase the potential difference, but in an optimum design, its effect is not significant.

DIGITAL IMAGE PROCESSING FOR EVALUATION OF PASPALUM MILLEGRANA SCHRAD ROOT SYSTEM1

ABSTRACT The characterization of the plant root system is of great importance for the understanding of its contribution to soil shear resistance, constituting an important tool for decision making in soil bioengineering works. The objective of this work was to evaluate the growth and distribution characteristics of the root system of Paspalum millegrana Schrad. grass in Entisol using Digital Imaging Processing (DIP). The data were obtained by opening a soil pit to expose the root system of Paspalum grass up to 1.70 m depth. The profile wall and volumetric ring methods were used to collect quantitative information of the root system. The SAFIRA software and the ArcMAP software belonging to the ArcGIS suite were used for image processing. The profile wall method showed that Paspalum grass has a large volume of roots in the first 0.40 m to 1.30 m soil depth. It was observed that the root length and volume of Paspalum grass reach depths beyond 1.70 m, which is important to increase soil resistance to erosion processes. The profile wall method when compared to the volumetric ring method proved to be more efficient to understand the behavior of the Paspalum grass root system since it enables an assessment of its spatial distribution with better detailing.

Soil Physical Quality After 21 Years of Cultivation in a Brazilian Cerrado Latosol

Long-term studies aiming soil quality evaluation under different soil management strategies are no common. Long-term evaluations provided more reliable contributions to decision-making and practices adoption. This study evaluated the soil physical quality of a Brazilian Cerrado Latosol after 21 years of three different soil management strategies: disc plowing (DP), no-tillage (NT), and disc harrowing+subsoiling (DHS). In comparison to the reference, a soil from a native Cerrado area, the removal of the original vegetation and the implementation of the three soil management strategies increased the soil bulk density (Bd) and reduced soil porosity, macroporosity, soil organic carbon (SOC) and the size of water-stable aggregates, but did not change the glomalin-related soil protein (GRSP) contents and clay flocculation. Similar effects were diagnosed on soil physical quality when is considered only the three different management strategies, especially on soil porosity, Bd, size of water-stable aggregates, SOC and GRSP contents. Strategies of DP and NT increased soil resistance to penetration in the superficial layers, while the annual use of DHS reduced this soil mechanical characteristic. The NT system did not provide increasing of soil organic carbon in comparison to other management practices evaluated. In conclusion, removing the native vegetation affected soil physical quality, but the Brazilian Cerrado soil is resilient to physical damage even when different intensive farming practices are implemented for more than two decades. The limitation of the NT system in improving the soil physical quality is related to climate conditions that determine the non-maintenance of straw on the soil surface.

Improvement stability of earth canal banks using geo-technical approaches

ABSTRACTSplash erosion is one of the common erosional features, which is happening in the steep slope of sidewall of earth structures. Accordingly, it is necessary to use erosion control procedures in some sections of the route, especially in the intersection with other structures or in the intervals of channel route in the vicinity of access road or agricultural lands. Application of bio-mulches and well-known natural modifying agents are being used to control erosion. This research aimed to control splash and rill erosion processes along the steep slope of sidewall of earth structures and to find out the best modifying agents and bio-mulches to enhanced stability of soil profile. The research method was formulated to use experimental methods to simulate rainfall in different intensities and durations using rain simulation laboratory of soil protection and watershed management research institute. In addition, modifying agents and bio-mulches were applied in order to discover optimum compounds to improve stability of soil resistance parameters on the sidewalls of irrigation and drainage channels. Further, geometry of the irrigation and drainage channels (Khuzestan Province, Southwestern of Iran) was use to setup experimental procedures. In total, 290 tests were conducted using 15 types of modifiers and bio mulches. The resultant data have emphasized on effectiveness treatments using bio-mulches and groups of cements such as sulfate, slurry and lime, and soil mixture with a confidence level of 95 percent. For instance, bio-mulches were increased soil resistance upon to 89% rate of erosion along the sidewalls of drainage channels. Sulfate resistant cement slurry treatment has represented the best performance among other soil-modifying agents with a rate of 98%. The present research has introduced applicability methods of the bio-mulch and soil-modifying agents in soil erosion control.

EFFECT OF VETIVER ROOTS ON SOIL RESISTANCE TO PENETRATION IN A TYPIC FLUVIC NEOSSOL IN THE SÃO FRANCISCO RIVERBANK

ABSTRACT The aim of this study was to evaluate the effect of the root of vetiver grass (Chrysopogon zizanioides (L.) Robert) on the soil Resistance to penetration (RP) in the margins of the lower São Francisco River. Vetiver grass seedlings were planted on the riverbank margins in order to increase soil resistance to erosion processes, and RP assessments were made at soil depths of 0-0.20, 0.20-0.40, and 0.40-0.60 m in different situations (near the plants and within rows). RP data was obtained using an automated penetrometer. Gravimetric moisture data was also collected, as well as particle size data by densimetry, and root density data by the monolith method. The results of the RP, moisture, and root density studies were subjected to analysis of variance (p &lt;0.05) and then the averages were compared by the Tukey test using SISVAR software. The samples next to the vetiver grass showed an average RP of 1793.94 kPa and an average moisture content of 11.78%, statistically differing from that of the sampled points within rows. RP and soil moisture did not differ statistically at the depth assessed. The vetiver grass produced an adequate ground cover, leading to higher water retention and hence a reduced resistance to penetration.