Modeling Solute Transport in Soil under Conventional Plow-Based and Conservation Agriculture Production Systems in Claveria, Misamis Oriental, Philippines

摘要

This study aimed to model and to compare the solute-transport behavior of soil under conservation agriculture (CA) and plow-based (PB) production systems in the Philippines. Undisturbed soil core samples were taken from both production systems from experimental sites in Claveria, Misamis Oriental, Philippines. A stochastic method, following continuous-input soil column tests, determined the dispersivity of the soil samples while a laboratory flow-through method, using pulse-input soil column tests, calculated the retardation factor. Both the soil dispersivity and the retardation factor were optimized using the CXTFIT model to fit the observed values to the Convection-Dispersion Equation (CDE). Upper-layer PB soil, with a combined lowest retardation factor of 1.26 and dispersivity of 17.5 cm, had the highest peak concentration of 0.67 C-0 and the shortest time-to-peak of 44 s. Soils under conservation agriculture production systems (CAPS), having a high retardation factor of 6.54 inspite of the highest value of dispersivity of 27.3, exhibited the lowest peak concentration of 0.44 C-0 after nearly 7 min of peaking time. These results may be indicative of higher soil organic carbon content in soils under CA. Model efficiencies ranging from 77% to 98% signify that the CDE is able to adequately. predict solute transport in these soils. Simulations of solute transport in response to changing soil organic carbon content for a 10-yr period were performed. Increasing the organic carbon by 30% in soils under CAPS reflects a 9.6% decrease in peak concentration and a 3.1% increase in time-to-peak. On the other hand, there are minimal changes in terms of both peak concentration and time-to-peak in soils under PB systems, assuming a 3% decrease in organic carbon.