|Mielke, Lloyd - RET USDA ARS EMPLOYEE|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 3, 1998
Publication Date: November 1, 1998
Citation: Mielke, L.N., Wilhelm, W.W. 1998. Comparisons of soil physical characteristics in long-term tillage winter wheat-fallow tillage experiments. Soil & Tillage Research 49:29-35. Interpretive Summary: Soil physical properties are strongly influenced by soil management practices and affect development and growth of both plants and microorganisms. Soil type and depth of tillage affected measured properties, but the greatest differences were in the surface soil layers. Parameters, such as water content, hydraulic conductivity, bulk density, ratio of air to water permeability, total porosity, and pore space, differed in the 0 to 3 and 3 to 6 inch layers, but were similar in the 6 to 12 inch layer. The sod treatment, which has never been tilled, usually had the most extreme value with the tilled treatment values clustered together at the opposite end of the range. Air to water permeability ratio is an indicator of structural stability where a value of one indicates the greatest stability. Based on this measure, the 0 to 3 inch layer in both soils used in this study, the Alliance and Durco soils, was more stable than the 3 to 6 inch layer. The Alliance soil, which had been cropped longer than the Durco soil, showed a tendency to have a less stable structural. Based on precipitation intensity records and infiltration characteristics, water would seldom run off the Duroc soil when planted to sod or wheat with sub-till or no-till. Results show that runoff would occur most frequently from the plow treatment in both soils.
Technical Abstract: Soil physical characteristics resulting from tillage of fallow-wheat cropping systems were compared for two soils in western Nebraska. Soil physical environment influences amount of water entering soil and the microenvironment that influences soil biological processes important to plant response. Effects of tillage on physical properties varied with soil type and depth of tillage. Generally, the 0 to 76 mm layer has the largest number of physical properties that differ as a result of tillage, however, only a few properties differed at deeper depths. The Alliance soil at the Previously Cultivated site showed differences in bulk density, hydraulic conductivity, ratio of air to water permeability, and total porosity for the 0 to 76 mm layer but only hydraulic conductivity differed at 76 to 152 mm. Similar frequencies of differences in physical properties were true for the 0 to 76 mm layer of the Duroc soil at the Native Sod site. Compared among treatments, water content, bulk density, and pore space differed in the 0 to 76 mm layer, while all properties differed in the 76 to 152 mm layer; there were fewer differences in the 152 to 304 mm layer. The sod treatment usually was the most extreme value with tilled treatment values clustered together. Air to water permeability ratio, an indicator of structural stability (1.0 being stable), indicted that surface soils (0-76 mm) were more stable than deeper layers in both soils. Duroc soil has not been cropped as long as the Alliance soil and showed a tendency to be more structurally stable. Based on precipitation intensity records and infiltration characteristics, water would seldom run off Duroc soil when in sod and with sub- or no-till. Runoff occurs most frequently from plow tx.