Soils textures

The texture of the soil refers to the amount of sand, silt, and clay contained in a soil sample. The distribution of particle sizes determines the soil texture, which can be assessed in the field or by an accurate particle-size analysis in the laboratory. The classification of the particle size according to Wentworth is provided in Table 14.9. 

Sand grains in the soil feel like abbrasives. 

Makes the soil feel smooth and soapy and only very sUghtly sticky. Makes the soil easy to rolled, sticky and plastic when wet or hard and cloddy when dry  

Note that a high organic matter content tends to sraoothen the soil and can influence the feeling of clay. 

Percentages of clay (less than 0.002 mm), silt (0.002 to 0.05 mm) and sand (0.05 to 2.0 mm) in the basic soil textural classes 

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Humus The dark organic material in soils, produced by the decomposition of soils. The matter that remains after the bulk of detritus has beenconsumed (leaves, roots). Humus mixes with top layers of soil (rock particles), supplies some of the nutrients needed by plants -increases acidity of soil inorganic nutrients more soluble under acidic conditions, become more available, EX. wheat grows best at pH 5.5-7.0. Humus modifies soil texture, creates loose, crumbly texture, that allows water to soak in and nutrients retained permits air to be incorporated into soil. 

Soil texture, or appearance, depends on particle size, shape, and gradation. Therefore, using the classification in Figure 2-60 the soil texture can be specified as sandy clay or clay-sand. 

To promote the use of poor quality water for irrigation, a field research study was conducted in three semi-arid regions with water scarceness in Syria in order to define, under field conditions, the wheat yield response function to irrigation water salinity, the effect of soil texture and structural characteristics on the irrigation water salinity threshold, and to compare this value with the conventional threshold value. 

There was a discrepancy between water salinity limits for the three locations, which may be attributed to factors related to difference in soil texture and stmcture. This affects soil infiltration capacity and water retention. These soil hydrologic characteristics influence salt development in the soil profile, which affects plant... 

The results of this research study indicate that wheat tolerance for irrigation with saline water is affected by various real in-field conditions, including soil texture and structure, climate, irrigation water management and agricultural practices. 

Soil textural aspects also influence bacterial survival, possibly by affecting... 

J. Hassink, Effects of soil texture and structure on carbon and nitrogen mineralisation in grassland soils. Biology and Fertility of Soils I4 26 (1992). 

Figure 2 Gradients in Rb around a maize root as visualized by autoradiography. The depletion of Rb depends on the diffusion coefficient (D,.) which in turn depends on the soil texture. (From Ref. 12.)...

Once the targeted study regions, soil textures, space requirements, and other key aspects of study design have been determined, the search for suitable test sites... 

Soil properties A Soil texture (sand, silt, clay), organic matter/carbon content, and pH Stones, roots, and hardpans must be largely absent to allow representative sampling of soil profile Soil properties should appear uniform over test site Soil texture data should be available at time of site selection. Soil properties must match study purpose. This can be realistic use conditions, realistic worst-case or worst-case in terms of agrochemical mobility and persistence Must ensure that the majority of samples can be taken from the deepest sampling horizon. Information about sub-soils can be obtained from soil maps, test coring and on-site interviews... 

Once test sites have been identified, control soil should be collected and returned to the laboratory. This soil is used to (1) verify soil texture and related properties, (2) ensure adequate analytical recovery of target analytes, and (3) determine the presence of potential background interferences in the soil. 

Keywords Methane, emissions, rice production, agriculture, soil texture... 

Brye KR, Rogers CW, Smartt AD, Norman RJ. Soil texture effects on methane emissions from direct-seeded, delayed-flood rice production in Arkansas. Soil Sci. 2013 178 519-529. 

Bioavailable trace elements in world arid and semi-arid soils vary widely, depending upon the nature of the parent materials, soil pH, CaC03 and clay content, and soil texture. The contents of bioavailable trace elements in arid and semi-arid soils of selected countries are presented in Table 7.6. The data are recalculated from Sillanpaa (1982) and cited from Liu (1996), Han and Banin (1997, 1999) and many others. 

The Naff-Larkin-Freeman association contains fine- to medium-textured soils, moderately-well to well-drained. The Garrison-Marble-Springdale soils, on the other hand, are gravelly and sandy (coarse-textured) and are "somewhat-excessively" to "excessively drained (USDA, 1968). In addition to the soil textures, water permeabilities are described qualitatively for these soils, leading to the estimated range of intrinsic permeabilities shown in Table III for these two soil associations. 

Needelman BA, Wander MM, Bollero GA, Boast CW, Sims GK, Bullock DG (1999) Interaction of tillage and soil texture biologically active soil organic matter in Illinois. Soil Sci Soc Am J 63 1326-1334... 

We can see that due to joint effects of aridity and soil texture, the dust emission rates increase from east to west by as much as 5 orders. The maximum emission rate is 1.5 ton/ha/yr. The total dust emission amount of the Gobi desert is estimated as 25 x 106 tons per year and that in spring is 15 x 106 tons per year. The seasonal dust emission amounts in summer, autumn and winter are 1.4 x 106, 5.7 x 106 and 2.9 x 106 tons, correspondingly. 

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