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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Soil Science Society of America journal 62 (1998), S. 764-773 
    ISSN: 1435-0661
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Zea mays L.) grain yield on a typic Fragiochrept soil on a hillslope to soil properties and topographic features. Corn grain yields were samples from a field that measured 280 by 150 m using a grid and five transects. One-hundred forty yield measurements were taken on the grid (1983-1985) and 190 measurements on the transects (1984 and 1985) from plots 5.3 m long and two corn rows wide. Measurements of soil surface elevations, soil organic matter (OM), P, and K contents were also taken at the grid plot locations. These data were analyzed using the methods of spectral analysis. Yield spatial and temporal variability was strongly related to surface undulations and the value of surface curvature was found to be a useful parameter to quantify variations in topography. The intra-annual differences in weather had the largest effect on grain yield at locations where the magnitude of curvature was large. Where the magnitude of curvature was small, the correlations of yield for the wet (1984) and dry (1985) years were highly significant. Yields correlated with soil P, K, and OM only in the dry year, 1985. Yields in the relatively dry years (1983 and 9185) correlated with depth to fragipan. Elevation data helped us interpret the spatial and temporal variability of grain yield by separation of areas with convex curvature from areas with concave curvature.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-0661
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: K s) using a modified Kozeny-Carman equation. This equation is of the form of a coefficient (B) multiplied by effective porosity raised to a power (n). The purpose of this study was to improve the predictive capability of the modified Kozeny-Carman equation by including information from moisture release curves (soil water content vs. matric potential relation). We fitted the Brooks-Corey (B-C) equation parameters (pore size distribution index and air entry potential) to moisture release data from a large database (〉500 samples). Values of K s were also available from the same source. Inclusion of the pore size distribution index into the Kozeny-Carman equation improved the K s estimation over using only effective porosity, but only slightly. The improvement came through a better estimation of large values of K s. We also fit a relationship for the coefficient (B) of the Kozeny-Carman equation as a function of the two B-C parameters with a constant value of n = 2.5 for the exponent. Overall the use of Brooks-Corey parameters from moisture retention data improved estimates of K s over using effective porosity (φe) alone. There is still considerable error in predicting individual K s values, however. The best forms of the equation was when λ was included in the term for the coefficient for the modified Kozeny-Carman equation. The next best form was when λ was included in the exponent for φe The two best models appeared to better preserve the mean, standard deviation and range of the original data.
    Type of Medium: Electronic Resource
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