Its sorry state is due to compaction from running machinery over it; water and wind erosion; and depletion of minerals and organic matter through overplanting and overgrazing.Related items A survey of agriculture and technology: Cultivating carbonMar 23rd 2000Salt, too, is building up through over-irrigation and poor soil drainage.
A recent World Bank reports says that land subsidence from compaction (from new skyscrapers, for instance) and increased groundwater extraction (for a growing population) mean that Jakarta is sinking ten times faster than the Java Sea is rising because of climate change.All across Asia, megacities face similar problems.
Both compaction and cementation decrease the porosity.
These long taproots also improve soil quality by decreasing soil compaction.
These coals formed from the carbonization of plant debris, and it is generally held that one metre of coal equals the compaction of approximately five times as much plant material.
In sedimentary rocks, the amount of pore space depends on the degree of compaction of the sediment (with compaction generally increasing with depth of burial), on the packing arrangement and shape of grains, on the amount of cementation, and on the degree of sorting.
The optimum water content for maximum dry density which results in maximum strength can be achieved for a given amount of work done on the soil in compaction.
Large raindrops, up to 6 mm (0.2 inch) in diameter, have terminal velocities of about 10 metres (30 feet) per second and so may cause considerable compaction and erosion of the soil by their force of impact.
The cells may be either empty or filled with mineral matter, and the cell walls may have been crushed during compaction (bogen texture).
Technological advances continued during the first half of the 20th century, including the development of garbage grinders, compaction trucks, and pneumatic collection systems.
Compaction reduces the volume of refuse in the truck to less than half of its loose volume.
