Integrated experimental and numerical assessment of acid buffer capacity evolution in soils

Assessment of acid buffering capacity loss in agricultural soils in the San Luis Valley requires an integrated experimental and numerical approach to evaluate multiple variables including soil composition, acidity of irrigation water, and rate of application. Sequential batch tests are designed to evaluate the effects of total acid loading on the soils. Two paths are followed in a 9-cell matrix: a path of increasing acid loading and a path of increasing soil exposure. Long term batch tests are designed to simulate the application of irrigation water to soil samples over an extended period of time under conditions similar to those of natural irrigation. A four-step sequential extraction scheme is used to aid in evaluating the mode-of-occurrence and concentrations of metals in soils before and after acid reaction. Experimental data are used to calibrate reaction path models which can be used to investigate soil response to irrigation variables in a time-effective manner.