Spatial and temporal variability of soil chemical parameters
Abstract
Soils vary widely in their chemical properties, spatially, and over time. The purposes of this study were to (1) assay the spatial pattern of soil chemical parameters and relate them to variations in landscapes, soils, and management practices; (2) determine the magnitude and pattern of time-dependent changes in the levels of pH and available nutrients; and (3) to relate these spatial and temporal variations to the cation exchange capacity (CEC) of the soil. Six Indiana fields, or portions of fields were sampled using a 15 by 30 meter grid pattern. Six locations within each field were selected and sampled for yields, and then soil sampled on a monthly basis for one year. The samples were analyzed for pH in water, 0.01M CaCl$\sb2$, 1.0N KCl, and SMP buffer; and also for soluble salts, available P, exchangeable K, Mg, Ca, CEC and organic matter. Computer generated three-dimensional surface nets were constructed from the analytical data obtained. Correlation analyses were performed to associate the pattern and magnitude of spatial and temporal changes of the chemical parameters to spatial variations in soil CEC. Statistical and visual analysis of our sampling data indicated that liming and nutrient application patterns, in addition to natural landscape changes, have a substantial impact on the spatial pattern of chemical property variations. Spatial variations in the levels of exchangeable K and Mg were positively correlated with soil CEC. Results also indicated that moderately low CEC soils, with mostly organic exchange sites, are subject to K leaching. PH levels showed complex, CEC related patterns. Significant summer declines in the levels of potassium, magnesium, and water pH occurred, while soluble salts tended to accumulate. In addition, the range in temporal variations of chemical parameters are roughly proportional to soil CEC. Thus the soil's CEC is responsible for a substantial portion of observed spatial changes in many soil chemical parameters, and moderates the relative impact of factors causing temporal variations.
Degree
Ph.D.
Advisors
Mengel, Purdue University.
Subject Area
Agronomy
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