Effects of a compact layer on soil O2 diffusion

Compact layer in a soil profile may decrease crop yields. One of the major problems is the poor aeration condition within and below the compact layer, resulting in low concentrations of oxygen (O2) that is needed for root growth. A one-dimensional mathematical model was employed to simulate effects of a compact layer on soil O2 diffusion within and below this layer under varying soil water and temperature regimes. Changes in physical conditions in the soil were imposed by daily cycles of incident radiation and periods of rainfall. Resulting rates of water infiltration, redistribution, and evaporation as well as concentrations of O2 as a function of time were obtained. Simulations show that O2 was depleted much faster in the soil with the compact layer than without this layer. The influence of soil water content near the root tip was also examined. High water content in the compact layer may have a detrimental effect on rhizosphere O2 concentration and thereby on root growth through the compact layer.