Soils, compaction

Small tire chips have also been utilized as a soil amendment to improve athletic playing fields (see Recreational surfaces). A patented process marketed under the trade name Rebound (fai Tire) combines cmmb mbber from scrap tires with composted organic material to reduce soil compaction, resulting in better athletic playing surfaces (52). Installations have been made in Florida, California, Colorado, Hawaii, Maryland, Michigan, Missouri, Nevada, Virginia, and Wisconsin. 

Small or moderate thickness of soil Where there is some soil, ground displacement will be greater and seismic waves will pass through the soil. There may be some settlement of the structure due to soil compaction. While the structure will now be less subject to seismic forces, this may prove to be a worse case, as in addition to the structure being subject to almost the full intensity of the earthquake, there may also be settlement of the soil, which may result in settlement of the structure and cause it to collapse or develop cracks. 

Moisture-content determinations provide data for estimating soil compaction and compressibility. If a soil is saturated, no volume change can occur without intake or discharge of water. 

Photosynthesis and gas exchange of leaves are affected by many stresses including drought, flooding, salinity, chilling, high temperature, soil compaction and inadequate nutrition. Many, but not all, of these stresses have symptoms in common. For example, stomatal conductance and the rate of assimilation of CO2 per unit leaf area often decrease when stress occurs. Further, it is possible that several of the stresses may exert their effects, in part, by increasing the levels of the hormone abscisic acid (ABA) in the leaf epidermis. This hormone is known to close stomata when applied to leaves. 

R. F. Grant, Simulation model of soil compaction and root growth I. Model development. Plant Soil 750 15 (1993). 

The density of soil may control the presence, absence, or density of roots found in a particular soil layer. The density of plant roots in a soil layer determines how much water plants can remove from the layer and its rate of removal. Soil compaction, in addition to inhibiting root growth, reduces soil-water-holding capacity. A model that does not consider the effect of soil density on water balance may produce significant errors in water balance estimates. 

The liner was first built on top of the underdrain, the soil compacted with a padfoot roller, and water ponded on top of the liner. Infiltrometers measured the rate of inflow, and a lysimeter measured the rate of outflow. The soil used in the experiment was highly plastic with a PI of 41%. 

The sediment section also accounts for soil compaction (using a first-order process) and deposition or removal of detached sediment (e.g. by wind). 

In addition to highly variable root to shoot ratios (0.01-1.22) the use of these values is complicated by (1) ratios that are hybrid, variety, and species-specific and (2) below-ground allocations that are impacted by stress (Herbert et al. 2001 Bradford et al. 2005 Amos and Walters 2006 Johnson et al. 2006). For example, Johnson et al. (2006) used root to shoot ratios of 0.82,0.55, and 0.62 for wheat (Triticum aestivum), com, and soybean (Glycine max), respectively whereas Amos and Walters (2006) reported that root to shoot ratios increased with N and P deficiencies and decreased with increasing water stress, population, shade, and soil compaction. 

Density Soil compactness, heavy soil weight... 

A 10-yd3 soil sample was excavated from the site, blended, and characterized for initial hydrocarbon content and nutrient content. The reactor was filled with soil compacted to field density (Figure 12.10). The tank at the bottom was filled with water nutrients and surfactants. Water from this tank was sprayed over the top of the soil at a rate that maintained aerobic conditions. A significant amount of LNAPL was initially released from the soil, which required additional air to be pumped into the well points to maintain favorable growth conditions. After 105 days of operation, more than 87% of the total aliphatics and 89% of the total aromatics were removed. 

Patterson, J. C., and D. L. Mader. (1982). Soil compaction. In Urban forest soils A reference workbook. P. J. Craul, USDA Forest Service Consortium for Environmental Forestry Studies, Syracuse SUNY College of Environmental Science and Forestry. Washington, D.C. 

Hansen, S. (1993). Ecological agriculture nitrogen balance in field influenced by fertilization and soil compaction Agronomic and environmental effects of fertilization and soil compaction. Doctor Scientarium Theses, 2. 

Thus, any reduction in vegetation cover causes a reduction in water retention and evaporation, which ultimately increases surface runoff and the mnoff concentration times [58]. Human-induced soil sealing and soil compaction has the same effect (Fig. 7). 

However, the main disadvantages of tillage are undoubtedly soil degradation, increased erosion, increased breakdown of organic matter, and soil compaction (Foshee et al., 1997). Tillage can also destroy or injure tree and vine roots at or below the cutting zone. 

Foshee, W.G., R.L. Raper, W.D. Goff, and M.G. Patterson (1997). Orchard floor practices affect soil compaction around young pecan trees. HortScience, 32 871-873. 

Tillage and the multiple machinery passes used in conventional tillage systems can lead to soil compaction, which increases water runoff, alters the desirable mix of air and water in soil pores, and reduces crop yields. Tractor wheel traffic reduced corn yields by as much as 50% in a Canadian study (Raghavan et al, 1978). 

Soil compaction was clearly very marked for the clayey and the organic soils, and to a lesser extent for the sandy one, because of the soils intrinsic characteristics. 

In many cases cultivated soils have compacted areas which can severely impair tree growth. Compaction in soil may be due to factors associated with soil formation or geology, or it may have been caused by mechanical pressure from machinery or by deposits by transport and ground-levelling vehicles. If the soil is compacted it is absolutely essential to loosen the subsoil (e.g. by trenching or deep cultivation) before a new orchard is set up. Dwarfing rootstocks for apples and pears (M9, M27, quince C), elder and small fruit trees are particularly sensitive to soil compaction. 

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