Conceptualization, C. All authors have read and agreed to the published version of the manuscript. We declare that we hold no financial or personal relationship with anyone or any organization that could inappropriately influence our research.
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Find articles by Bangwei Huang. Author information Article notes Copyright and License information Disclaimer. Received Feb 4; Accepted Feb This article has been cited by other articles in PMC. Abstract As a constructed wetland ecosystem, paddy field plays an irreplaceable role in flood storage and detention, groundwater replenishment, environmental protection, and ecological balance maintenance. Keywords: new paddy field construction, shear strength, cohesion, water content, permeability property.
Open in a separate window. Figure 1. Materials and Methods 2. Figure 2. Figure 3. Sampling and Physical Properties of the Test Soils Ten kilograms of soil samples with a depth of 5—20 cm were collected at each sample point in the study area to remove large gravel blocks, animal and plant residues, and other impurities. Table 1 The physical properties of the test soils at different sample points.
The Determination of Permeability Coefficient and Shear Strength Characteristics The soil permeability coefficient was measured by using a TST permeameter variable-head permeameter produced by Nanjing Soil Instrument Factory, in which the bulk density was set to six gradients 1. Results 3. The Relationship between the Shear Stress and Displacement The shear strength of the soils under seven water contents and four vertical pressures was measured by a strain-controlled direct shear apparatus.
Figure 4. Effect of Water Content and Vertical Pressure on Shear Strength A direct shear test is used to determine the relationship between the shear stress and shear displacement under different vertical loads. Figure 5. Water Sensitivity Characteristics of the Shear Strength Parameters Cohesion is caused by the gravitational interaction between soil particles, and the water content is the main influencing factor for a particular soil mass. Figure 6. Figure 7. Permeability Characteristic of the Test Soils The permeability characteristics of the test soils were analyzed under different bulk densities 1.
Figure 8. Discussion 4. The Shear Strength of the Test Soils Decreases Obviously with Increasing Water Content The occurrence of soil damage is often caused by the destruction of internal soil particles, and the shear strength is an important indicator reflecting the ability of soil to resist shear damage.
The Permeability of Paddy Field Soils Has an Important Influence on the Construction and Operational Processes of Engineering Projects In the actual process of engineering construction, changes in soil water content and seepage state will lead to changes in soil stress, resulting in the collapse or dry shrinkage deformation of soils.
Conclusions The shear and permeability properties of soils under different land use types for engineering of new paddy field construction were investigated in a hilly mountainous region in southwestern China. Appendix A Table A1 The importation of soils at different sample points. Author Contributions Conceptualization, C.
Conflicts of Interest We declare that we hold no financial or personal relationship with anyone or any organization that could inappropriately influence our research. References 1. Chen L. Soil characteristic response times and pedogenic thresholds during the year evolution of a paddy soil chronosequence. Soil Sci. Goswami S. Crop residue management options in rice-rice system: A review. Biogeochemistry of paddy soils. Mueller-Niggemann C.
Distribution of tetraether lipids in agricultural soils—Differentiation between paddy and upland management. Timsina J. Productivity and management of rice-wheat cropping systems: Issues and challenges. Field Crops Res. Xue B. Roles of soil organic carbon and iron oxides on aggregate formation and stability in two paddy soils. Soil Tillage Res. Wang W. Effects of rice straw incorporation on active soil organic carbon pools in a subtropical paddy field.
Cui J. Physical and chemical stabilization of soil organic carbon along a year cultivated soil chronosequence originating from estuarine wetlands: Temporal patterns and land use effects. Origin of subsoil carbon in a Chinese paddy soil chronosequence. Cao Z. Science Press; Beijing, China: In Chinese [ Google Scholar ]. Rachman A. Influence of long-term cropping systems on soil physical properties related to soil erodibility.
Wei Y. The effect of water content on the shear strength characteristics of granitic soils in South China.
Wuddivira M. Influence of cohesive and disruptive forces on strength and erodibility of tropical soils. Zhang B. Soil Mechanics and Foundation China. Horn R. Stress-strain effects in structured unsaturated soils on coupled mechanical and hydraulic processes.
Rahardjo H. Shear strength of a compacted residual soil from consolidated drained and constant water content triaxial tests. Hoyos L. Residual shear strength of unsaturated soils via suction-controlled ring shear testing.
Variability of residual soil properties. Fasinmirin J. Strength and hydraulics characteristics variations within a tropical Alfisol in Southwestern Nigeria under different land use management. Paddy Soils of China. Han Z. Response of soil erosion and sediment sorting to the transport mechanism on a steep rocky slope. Earth Surf. Wei C. Anthropic pedogenesis of purple rock fragments in Sichuan Basin, China.
Dane J. Zhong S. Shear strength features of soils developed from purple clay rock and containing less than two-millimeter rock fragments. Guo N. The signature of shear-induced anisotropy in granular media. The water carries dissolved minerals salts that accumulate in the soil as the water is evaporated from the soil surface or transpired through the plants to the atmosphere. In general, these soils are not recommended for irrigation. Saline and sodic soils may be of natural or man-made origins.
One of the man-made processes is related to irrigation. Under some conditions, sodium can be controlled in the upper part of the soil through the use of soluble calcium amendments. The replacement of sodium by calcium improves the structure of the soil. Calcium soil amendments can be helpful in situations where land with a majority of unaffected irrigable soils contains pockets inclusions of sodium-affected soils.
Under irrigation, calcium soil amendments will help where surface crusting has become a problem. Special irrigation management practices may be required on these soils. Leaching or controlling the water table elevation can manage salt concentrations. Leaching is accomplished by applying more water than the soil will hold in the root zone. Large rainfall events, applying additional irrigation water or both will carry some of the salts below the root zone.
Planting a deep-rooted crop, such as alfalfa, or installing subsurface drainage can accomplish water table control. Deep ditches and tiling are methods of subsurface drainage that have been used successfully in many parts of the world to control the level of the water table.
Soil salt and sodium contents need to be measured to determine precisely the severity of the problem. The salt content of the soil is estimated from an electrical conductivity measurement using one of the following: a soil water extract, soil water slurry or soil paste.
The sodium content of the soil often is measured on a soil water extract and expressed as the ratio between the sodium and calcium plus magnesium; it is given the term sodium adsorption ratio SAR. Soil sampling the surface layer top 6 inches on a periodic basis every three to five years will track the change in accumulated salt or sodium. The SAR of the soil samples will indicate if a buildup of sodium has occurred. Generally, soils with an SAR of 13 from the saturated extract will exhibit significant physical problems due to dispersal of clay particles.
Usually a soil with an SAR of 6 or lower from the saturated extract will not have physical problems associated with dispersed clay. However, if periodic sampling indicates that the SAR is increasing, say from 6 to 9, then you may need to consider corrective action. Topography, or the "lay of the land," has a large impact on whether a field can be irrigated.
Relief is a component of topography that refers to the difference in height between the hills and depressions in the field. The topographic relief will affect the type of irrigation system to be used, the water conveyance system ditches or pipes , drainage requirements and water erosion control practices. The shape and arrangement of topographic landforms and the type of surface waterway network also will influence irrigation management. For example, a low spot in the field where water typically accumulates after a rain may become a place that is continually wet with the addition of irrigation water.
With some crops, such as potatoes, a wet low spot could become a source of disease. For a center pivot, a tower that travels through the low spot could become stuck. Slope is important to soil formation and management because of its influence on runoff, soil drainage, erosion, the use of machinery and choice of crops. Slope is the incline or gradient of a surface and commonly is expressed in percents. The percent of slope is determined by measuring the difference in vertical elevation in feet over feet of horizontal distance.
For example, a 5 percent slope rises or falls 5 feet per feet of horizontal distance. The shape of the slope is another important characteristic. A convex slope curves outward like the outside surface of a ball, a concave slope curves inward like the inside surface of a saucer, and a plane slope is like a tilted flat surface.
Slopes are described as simple or complex. Simple slopes have a smooth appearance, with surfaces extending in one or perhaps two directions. For example, slopes on alluvial fans and foot slopes of river valleys are regarded as simple. Complex areas have short slopes that extend in several directions and consist of convex and concave slopes much like the knoll and pothole topography found on glacial till plains. Gravity surface irrigation can be used only on simple slopes of 2 percent or less.
In general, simple and complex slopes greater than 1 percent should be irrigated only with sprinkler or drip systems. Center pivot sprinkler irrigation systems can operate on slopes up to 15 percent, but generally simple slopes greater than 9 percent are not recommended.
To accommodate gravity or sprinkler irrigation systems, land smoothing can be used to modify the slope in a field. However, land smoothing may cause yield reductions for one to three growing seasons.
The places where topsoil was removed are most likely to have yield reductions. Special management using increased organic matter may be required to accelerate soil building in these areas. The quality of some water sources is not suitable for irrigating crops. Irrigation water must be compatible with the crops and soils to which it will be applied. A water analysis and legal description of the land proposed for irrigation are required before a recommendation can be made.
The quality of water for irrigation purposes is determined by its total dissolved salt content. An analysis of water for irrigation should include the cations calcium, magnesium and sodium and the anions bicarbonate, carbonate, sulfate and chloride. Because some crops are sensitive to boron, it often is included in the analysis. The two most important factors to look for in an irrigation water quality analysis are the total dissolved solids TDS and the sodium adsorption ratio SAR.
The TDS of a water sample is a measure of the concentration of soluble salts in a water sample and commonly is referred to as the salinity of the water. EC can be expressed in many different units, and this often causes confusion. On an irrigation water test report, you might see one of the following units The SAR of a water sample is the proportion of sodium relative to calcium and magnesium.
Because it is a ratio, the SAR has no units. Laboratories that perform irrigation water analysis may provide a suitability classification based on a system developed at the U. Salinity Laboratory in California Figure 5. This classification system combines salinity and sodicity.
For example, a water sample classified as C3-S2 would have a high salinity rating and a medium SAR rating. Figure 5. Diagram showing the classification of irrigation water. From Agriculture Handbook No. The scale for sodicity is not constant because it depends on the level of salinity.
In general, any water with an EC greater than 2, or an SAR value greater than 6 is not recommended for continuous irrigation in North Dakota. In cases where sporadic irrigation is practiced a particular piece of land is irrigated one year out of three or more , lower-quality water may be used. Calcium added to irrigation water can lower the SAR and reduce the harmful effects of sodium.
The effectiveness of added calcium depends on its solubility in the irrigation water. Calcium solubility is controlled by the source of the calcium for example, calcium carbonate, gypsum, calcium chloride and the concentration of other ions in the irrigation water.
Compared with calcium carbonate and gypsum, calcium chloride additions will result in higher concentrations of soluble calcium and be the most effective at lowering irrigation water SAR. However, calcium chloride is considerably more expensive than calcium carbonate and calcium sulfate gypsum. C1 - Low-salinity water: Can be used for irrigation with most crops on most soils with little likelihood that soil salinity will develop. Some leaching is required, but this occurs under normal irrigation practices except in soils of slow and very slow permeability.
C2 - Medium-salinity water: Can be used if a moderate amount of leaching occurs. Plants with moderate salt tolerance can be grown in most cases without special practices for salinity control.
C3 - High-salinity water: Cannot be used on soils with moderately slow to very slow permeability. Even with adequate permeability, special management for salinity control may be required and plants with good salt tolerance should be selected. C4 - Very high salinity water: Is not suitable for irrigation under ordinary conditions but may be used occasionally under very special circumstances.
The soils must have rapid permeability, drainage must be adequate, irrigation water must be applied in excess to provide considerable leaching, and very salt-tolerant crops should be selected. S1 - Low-sodium water: Can be used for irrigation on almost all soils with little danger of the development of harmful levels of exchangeable sodium. S2 - Medium-sodium water: Will present an appreciable sodium hazard in fine-textured soils, especially under low leaching conditions.
This water may be used on coarse-textured soils with moderately rapid to very rapid permeability. S3 - High-sodium water: Will produce harmful levels of exchangeable sodium in most soils and requires special soil management, good drainage, high leaching and high organic matter additions. S4 - Very high sodium water: Generally is unsatisfactory for irrigation purposes except at low and perhaps medium salinity.
Carbonate and bicarbonate ions in the water combine with calcium and magnesium to form compounds that precipitate out of solution. The removal of calcium and magnesium increases the sodium hazard to the soil due to the irrigation water.
The increased sodium hazard often is expressed as "adjusted SAR. Nozzles of sprinkler systems have been plugged by carbonate minerals in some states but this has not been observed in North Dakota. However, carbonate minerals have plugged the emitters in drip irrigation systems in North Dakota.
To control this problem, add a mild acid to lower the pH of the irrigation water. Boron is essential for the normal growth of all plants, and the quantity required is low compared with other minerals. However, some plants are sensitive to even low boron concentrations. Dry beans are very sensitive to small amounts of boron, but corn, potatoes and alfalfa are more tolerant.
In fact, the concentration of boron that will injure the sensitive plants often is close to that required for normal growth of tolerant plants. Although no problems with boron in water used for irrigation in North Dakota have been documented, testing for this element in irrigation water is a precautionary practice.
Boron does occur in some North Dakota ground water at concentrations that are theoretically toxic to some crops. A boron concentration greater than 2 parts per million ppm may be a problem for certain sensitive crops, especially in years that require large quantities of irrigation water.
Soil is a medium that stores and moves water. If a cubic foot of a typical silt loam topsoil were separated into its component parts, about 45 percent of the volume would be mineral matter soil particles , organic residue would occupy about 5 percent of the volume and the rest would be pore space. The pore space is the voids between soil particles and is occupied by air or water. The quantity and size of the pore spaces are determined by the soil's texture, bulk density and structure.
Water is held in soil in two ways: as a thin coating on the outside of soil particles and in the pore spaces. Soil water in the pore spaces can be divided into two different forms: gravitational water and capillary water Figure 6.
Gravitational water. The pore spaces are Capillary water is held in the pore space against the force filled with water in excess of their capillary capacity, of gravity. Figure 6. When soils become dispersive, because of the accumulation of salts by evaporation, this can cause an order of magnitude drop in the permeability.
International Conventions and agreements. Although attention is given to soil depth and erosion as key indicators, a good case could be made for soil permeability as it gives early warning. It is not just soil depth that is important but the capacity of the soil to store water and to retain its integrity under the forces of erosion.
Secondary objectives of the indicator. As a general measure of soil quality and management performance. Definitions and basic concepts. In arid, semi-arid and dry sub-humid areas, soil permeability is spatially and temporarily highly variable.
Distinctions are made between the types of macro-meso-micro permeability that occur on cultivated and natural systems. With macro-permeability, there may be a ploughpan with a low permeability at a depth of about 30 - 40 cm. At the micro scale, permeability reflects the activities of soil organisms. Irrigation can have a negative impact on permeability if soils are not managed properly.
Values of permeability are highly variable in semi-natural systems e. During rainfall values decline as soils respond to wetting. Macro pores mean that very highly permeable conditions frequently exist adjacent to zones of low permeability.
Methods of measurement. In situ measurements and estimations can be made using improvised ring infiltrometers constructed from cans, or by augering a hole and measuring the rate at which water poured into it declines during a specified period of time.
With a ring, the water should be kept at a constant head about 3 cm above the surface and the amount of water added to the ring recorded. Field testing kits are described in the literature. Rain water or demineralised water should be used for the test. For larger areas rainfall simulation experiments can be used.
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