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Spatial Variability in Soils below Depth of Tillage: Bulk Density and Fifteen Atmosphere Percentage
Author(s) -
Cassel D. K.,
Bauer Armand
Publication year - 1975
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1975.03615995003900020011x
Subject(s) - loam , soil water , silt , soil science , bulk density , spatial variability , atmosphere (unit) , zoology , tillage , mineralogy , environmental science , geology , hydrology (agriculture) , mathematics , geomorphology , physics , agronomy , geotechnical engineering , biology , meteorology , statistics
Soil bulk density ( D b ) and the 15‐atm percentage (FAP) were measured for three soils—Maddock sandy loam (Site 1), Bearden silty clay (Site 2), both of glacio‐lacustrine origin, and Heimdal silt loam (Site 3) of glacial origin. D b and FAP were measured in approximately 30‐cm increments from a depth of 30 to 152 cm. In addition, D b and FAP were measured in the 15‐ to 30‐cm increment at Sites 2 and 3. A total of 192, 144, and 72 observations/increment for D b and FAP were made at Sites 1, 2, and 3, respectively. D b was greatest at Site I and had the greatest coefficient of variation (C.V.), being about 9%. The C.V. for D b for Bearden sic and Heimdal sil were approximately 6%. Mean values of FAP were approximately 4, 19, and 7% with C.V.'s of approximately 45, 14, and 19% found for Sites 1, 2, and 3, respectively. A sample calculation is presented which shows the number of D b and FAP measurements necessary to determine the unavailable water capacity within arbitrarily specified limits.