Idealized soil

The ideal soil is defined as a loose, granular medium that is devoid of cohesion but possesses internal friction. In contrast, an ideal cohesive medium is one that is devoid of internal friction. Real soils generally fall between the foregoing two limiting definitions. 

Forage legumes, of which white clover is the most important, are particularly sensitive to calcium deficiency and will not thrive. Ideally, soil pH should be maintained between 5.8 and 6.5. Heavy-textured soils such as clay require more lime than sandy soils to raise pH, because the higher levels of clay and organic matter act as a buffer against change, and the same is true of peaty soils. 

Consider an idealized soil containing ferric hydroxide and readily decomposable organic matter. The following conditions hold ... 

Figure 4.7 Calculated changes in pe, pH, [O2] and [Fe +] in an idealized soil during reduction. Mineral phases Fe(OH)3 and Fe3(OH)g. Parameters for pH buffering and cation exchange differ between (a)-(d) as indicated. Units of fees (soil pH buffer power), mmolkg pH CEC (initial cation exchange capacity), cmolc kg and [X ]l (concentration of non-carbonate anions), mM. CO2 pressure = lOkPa, 9 = 0.6, p = 1.0, initial pH = 4.5...

The key to ensuring that garden soil is in a proper chemical condition is to make certain that the soil pH and nutrient element status are correct for the crops of interest. Each crop has one pH value at which it grows best. Normally, the higher the amount of organic matter in the soil, the lower is the ideal soil pH. 

Gardner and Widstoe (1921) made attempts to develop a general equation. They assumed an ideal soil to be one in which the capillary potential was a linear function of the reciprocal of the moisture-content (after Buckingham, 1907), and that the inherent moisture conductivity is independent of the moisture-content. These assumptions are necessary for mathematical reasons. For downward flow through sand, whose surface is kept saturated, the equation connecting the time t and distance from the surface L was as follows ... 

Liquid Rising—Let us consider an ideal soil made up of spheres in closest packing, and direct our attention to just two rows of such a packing as shown in Figure 85. Haines has shown that there are two... 

Studies on soil physics. II. The permeability of an ideal soil to air and water. Ibid., 5 1-26. 

For use on croplands, the ideal soil-borne herbicide is selective against the weeds, is tolerated by the crop, and at practical dosages should break down in the soil within one season so as not to leave a toxic residue for a subsequent crop. For use as a soil sterilant, a compound should resist leaching and breakdown so as to remain active in the soil for many years. 

Fig. 4.21 Idealized soil profile showing master soil horizons and horizon abbreviations. The 0, A, E and B master horizons can be further subdivided into subordinate horizons depending on composition (see Figs 4.23M-.25). Note that the O horizon is composed of fresh (L) and partially decomposed (F) organic litter. Soil profiles are typically 0.5-1.0m thick such that master horizons are typically centimetres to tens of centimetres thick. SOM, soil organic matter CEC, cation exchange capacity.

Peat humic acid Ideal soil 58.3 4.97 32.2 2.62 Christman and Oglesby (1971)... 

It is generally assumed that for soft, saturated clays 4> is close to zero, and that for granular soils C is equal to zero. Thus, for ideal soils, shear strength can be approximately represented by straight lines on diagrams as shown in Figure 2.3. These lines are called failure lines, because a state of stress which would plot above them represents a failure condition. 

These data of Dittmer, and of Pavlychenko, serve to emphasize very dramatically the importance of roots in aggregate formation and in the overall build-up of an ideal soil structure that leads to good tilth and aeration, as well as to water-holding power and ready drainage. Roots themselves are major factors in producing the conditions that they themselves require. 

Numerous studies are reported on the electrokinetic removal of heavy metals from soils (Chapter 4). Many of these studies used ideal soils, often kaolinite, as a representative low-permeabiUty soil, which were spiked with a selected single cationic metal (such as lead and cadmium) in predetermined concentration. The spiked soil is loaded in a small-scale electrokinetic test setup and electric potential is applied. The transport and removal of the metal after specified test duration are determined. It is shown that cationic metals exist in soluble ionic form due to reduced pH near the anode regions and they are transported toward the cathode. However, when they reach near the cathode, they get sorbed or precipitated due to increased pH resulting from OH transport from the cathode. The actual removal from the soil is often negligible. 

Numerous bench-scale studies that use ideal soils such as kaolin spiked with a selected single contaminant (e.g. lead or phenanthrene) to understand the contaminant transport processes have been reported. However, only a limited number of studies have been reported on real-world soils contaminated with a wide range of aged contaminants, and these studies have been helpful in recognizing complex... 

Pyrophyllite clay is known to contain approximately 60% silica of which about 85% is non-crystalline, round amorphous silica molecules. This amorphous construction gives the clay particles an exceptional amount of free surface area to attract and hold toxic compoimds, and offer its nutrients to the soil and plants. Silica-rich naturally cleans up polluted land as it increases mineral content within the soil and builds nutrients within the plant. Silica-rich pyrophyllite clay holds the potential of being an ideal soil amendment. With... 

A. J. M. Spencer. "A theory of the kinematics of ideal soils under plane strain conditions," /. Mech. Phys. Solids, 12, 337-351, 1964. 

Lettuce can be grown on a wide variety of soil types. An ideal soil has good water retention properties but is not too heavy as this may limit field access by machineiy for planting, crop applications or harvest if wet. Very light soils may require frequent irrigation and additional fertiliser appUcations. 

H.L. Morrison and O. Richmond, Application of Spencer s ideal soil model to granular materials flow, Trans. ASME J. Applied Mechanics 43, pp.49-53 (1976). 

Adjusting soil pH - Ideal soil pH is between 6.5 and 8.5 check pH annually and if soil acidity increases (the lower the number the greater the acidity) consider spreading lime to raise soil pH. Lime is cheap, effective and easy to spread. Unfortunately, it is not a permanent solution. 

Fisher, R.A. 1926. On the capillary forces in an ideal soil. Correction of formulae given by W.B. Haines. Journal of Agricultural Science 16 492—505. 

Haines, W.B. 1925. Studies in the physical properties of soils. II. A note on the cohesion developed by capillary forces in an ideal soil. Journal of Agricultural Science 15 525-535. 

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