Effect of irrigation from a point source (trickling) on oxygen flux and on root extension in the soil

A two-dimensional trickle-irrigated soil model was examined in order to determine its aeration regime. Oxygen diffusion rate (O.D.R.) was used as an index of the soil aeration regime, and its influence on the development of root systems was determined. Volumetric soil air content was calculated from soil water tension data, using a retention curve. The root system was markedly concentrated at the periphery of the trickle-irrigated soil volume, while in the center there were few roots. An exponential correlation was found between root distribution and O.D.R., in which 20×10^-8g O₂×cm^-2×min^-1 was the critical value for root growth. There was a linear correlation between O.D.R. and volumetric air content which was affected by diffusion distance.