Evidence soil moisture

The moisture removal from the subslab can be very substantial, and could amount to many gallons of water per day.13-15 Unless the piping design allows for that water to drain back into the soil, the water could block flow of air in the piping or interfere with the fan operation. Evidence of moisture and other debris has also been found in the staining of roofs near the exhaust pipes of the SSD systems. 

Much of what we know about the nutrient stocks of secondary forests is based on soil measurements made to depths of only 0.1 to 1.0 m (Uhl and Jordan, 1984, Buschbacher et al., 1988, Koutika et al. 1997, Neill et al. 1997). However, water balance studies and direct measurements of deep soil moisture and roots provide evidence that forests across much of seasonally dry Amazonia depend upon root systems that extend well beyond this conventional sampling depth to absorb water during the dry season (Nepstad et al. 1994, Jipp et al. 1998, Hodnett et al. 1997, Holscher et al. 1997). The occurrence of root systems extending to 18 m depth in Amazonian forests (Nepstad et al. 1994) demands a re-examination of our thinking about the nutrient stocks of these ecosystems, and the recovery of these nutrient stocks in secondary forests. If the rooting zone of Amazonian forests extends to several meters depth, instead of several centimeters depth, are these forests less vulnerable than previously believed to nutri-... 

Soil structure, geologic strata, and topography influence the location and movement of variable source areas of surface runoff in a watershed. Eragipans or other layers, such as clay pans of distinct permeability changes, can determine when and where perched water tables occur. Shale or sandstone strata also influence soil moisture content and location of saturated zones. For example, water will perch on less permeable layers in the subsurface profile and become evident as surface flow or springs at specific locations in a watershed. Converging topography in vertical or horizontal planes, slope breaks, and hill slope depressions or spurs, also influence... 

From the examples given here, it is evident that soil adhesion can be reduced by surface modification through the application of a coating that minimizes adhesion or by forming a layer of water between the contact surfaces. The adhesion depends on the soil moisture content and the soil particle size distribution. By changing the moisture content and by the use of electroosmosis, the adhesion of soil to solid surfaces can be reduced. 

Soil moisture regime dry to aquic. Major soil property featureless soil bodies. Diagnostic horizons typically absent, albic. Epipedon ochric. Characteristics little or no evidence of soil development. Description recently formed soils such as land surfaces that are very young (e.g., alluvium, colluvium, mudflows), extremely hard rocks, sandy parent material, disturbed material (e.g., mined land, highly compacted soils, or toxic material disposal). Exhibit A/C or A/R profiles. May have an Ap horizon. 

Evidently the ideal sampling depth from the viewpoint of a constant Rn signal is 2 m or more. In practice such a depth is seldom attained because of practical difficulties. Quite often overburden thicknesses are less than 2 m, and as was shown above, variation in depth from site-to-site in near-surface surveys can have a pronounced effect on the soil-gas Rn concentration, apart from any meteorological variations. The meteorological variables responsible for these large changes in the soil-gas Rn concentration are barometric pressure, moisture content of soil, wind, temperature, convection and Earth tremors. 

Since this early discovery there has been considerable appreciation for the role of the soil microbial community in pesticide transformations. In some cases the role of microorganisms has been stressed by comparison of degradation rates in natural and sterilized systems (32), while in others researchers have chosen to use isolation of pesticide-degrading microorganisms from soil sis evidence of microbial involvement (33). It has also been recognized that environmental conditions that influence microbial activity (temperature, moisture,...) affect the microbial degradation of pesticides in soil (34). The importance of microbial involvement is demonstrated by the many reviews of pesticide/microbe interactions that have appeared (35-41). 

A cement floor. Not absolutely necessary but highly desirable, a cement floor is easy to work on, prevents migration of water to the earth and prevents soil and unwanted soil organisms from contaminating the pile. Water leaching from the pile, a good indicator of compost moistures, is quite evident on a cement floor. If a cement floor is not available, a sheet of heavy plastic can be used. 

---