Soil compaction is the process of densification in which porosity and permeability are reduced, strength is increased, and other soil characteristics and properties change. A compacted soil can be less productive, require more inputs, and increase contaminant export to the environment. In general, all cropland soils are compacted to some degree when compared to the natural state of a soil. A common measure of soil compactness is bulk density or measures of porosity derived from it, and other measures have been used as well. There is no consensus on a measure of soil compaction and no systematic monitoring program for this property.
Saline soils contain sufficient soluble salts to adversely affect plant growth.
Reclaiming saline soils economically is difficult, if not impossible. Irrigation in arid and semiarid regions often concentrates salts in soil and water, sometimes creating severe production and environmental problems. Dryland cropping systems that utilize long fallow periods can lead to leaching of salts and movement to low areas forming saline seeps. There is limited data on the area affected by salinity but recent surveys suggest that it is growing. Additionally, external factors, including acid precipitation, may acidify soils.