Laboratory Measurements of Hydraulic and Compressibility Characteristics of Fertilizer Treated Sandy Soils

Hydraulic conductivity and soil compressibility are known to be interdependent characteristics of soils. For agriculturally productive regions, such as San Joaquin Valley (SJV) in central California, certain agriculture practices, for example, overdraft of groundwater during drought periods, have caused excessive settlements in the region. While the effect of pumping has been extensively studied and monitored, the impact of other agricultural practices, such as fertilizer usage, is understudied. Therefore, an experimental study was undertaken to examine and compare changes in hydraulic conductivity and compressibility characteristics of soil treated with variable fertilizer concentrations. The results indicated the hydraulic conductivity increased, compression index decreased initially and then increased, and the coefficient of consolidation decreased with the increase in fertilizer concentration. An example of field application is included to illustrate the effect of changed characteristics on settlement estimations. Based on these findings, the authors conclude that fertilizer treatments were found to initiate changes in soil's hydraulic characteristics and may accelerate consolidation settlements.