Iowa Soil Bulk Density – 1/3 Bar Maps [gSSURGO]

Bulk density, one-third bar, is the oven-dry weight of the soil material less than 2 mm in size per unit volume of soil at water tension of -0.33 bar (-33 kPa), expressed in grams per cubic centimeter. Bulk density data are used to compute linear extensibility, shrink-swell potential, available water capacity, total pore space, and …Continue reading “Iowa Soil Bulk Density – 1/3 Bar Maps [gSSURGO]”

Iowa Soil Organic Matter Maps [gSSURGO]

Organic matter is the plant and animal residue in the soil at various stages of decomposition. The estimated content of organic matter is expressed as a percentage, by weight, of the soil material that is less than 2 mm in diameter. The content of organic matter in a soil can be maintained by returning crop …Continue reading “Iowa Soil Organic Matter Maps [gSSURGO]”

Iowa Soil Available Water Capacity Maps [gSSURGO]

Available water capacity (AWC) refers to the volume of water held per volume of soil that is available for plant uptake. This water typically occurs between suction levels of ~ -10 kPa (field capacity) and -1,500 kPa (wilting point). The capacity for water storage is given in centimeters of water per centimeter of soil for …Continue reading “Iowa Soil Available Water Capacity Maps [gSSURGO]”

Selected highlights in American soil science history from the 1980s to the mid-2010s

Despite the soil science discipline in the USA hitting hard times in the 1980s and 1990s, there were still many positive advances within soil science in the USA during these two decades. There was an increased use of geophysical instrumentation, remote sensing, geographic information systems (GIS), and global positioning systems (GPS), and research began in digital soil mapping, all of which lead to better understanding of the spatial distribution and variability of soils. Digital soil mapping is being incorporated into the National Cooperative Soil Survey, and the impact of humans on the soil system is being fully recognized. The expansion of soils into new areas and widening recognition of the importance of soils gives the field hope for a bright future in the USA.

History of soil geography in the context of scale

Categories of cartographic scale correspond to the selection of environmental soil predictors used to initially create historical soil maps. Paradigm shifts in soil mapping and classification can be best explained by not only their correlation to historical improvements in scientific understanding, but also by differences in purpose for mapping, and due to advancements in geographic technology. Although the hierarchy of phenomena scales observed in this study is generally known in pedology today, it also represents a new view on the evolution of soil science.