Submitted to: ARS Workshop on Real World Infiltration
Publication Type: Government Publication
Publication Acceptance Date: July 25, 1996
Publication Date: N/A
Interpretive Summary: Ensuring the supply and quality of water for drinking water and crop production is a critical issue for our survival. The complex phenomenon of water infiltration into the soil plays a major role in the hydrologic cycle. Much is know about how water infiltrates the soil, yet we are unable to predict with reasonable certainness the rate that water will infiltrate the soil, or how much will run off carrying soil and nutrients with it. This lack of predictive capability is in large part a result of the magnitude of the temporal and spatial variability of infiltration. Temporal variability, macroporosity, and bioactivity (including plant growth) are so intertwined as to be inseparable and are the major source of temporal variability in infiltration. Numerous research papers have confirmed the idea that temporal variability of the soil fabric far exceeds spatial variability across a landscape and should be considered as a major area of future research. This paper reviews the current status of knowledge regarding the dynamic interrelationships of infiltration, macroporosity, and the growth and death of plants. The paper concludes with recommendations for the direction of future infiltration research.
Macroporosity and bioactivity, including plant growth, are inseparably intertwined with infiltration, and are the major sources of temporal variability in the rates of water infiltration. The larger pores of the soil fabric are dynamic and change with both natural and man made activity, causing most of the temporal variability of infiltration. These pores are largely created by bioactivity (roots and burrowing fauna), but may also be created by tillage operations, soil shrinkage, and aggregation. Numerous research papers have shown that temporal variability of the soil far exceeds spatial variability across a landscape and should be considered as a major area of future research. Vulnerability of the soil fabric to change and the agents which cause changes are important components of temporal variability. The less stable the soil fabric and the more exposed a soil is to the agents of change, the greater will be the observed temporal change. Some agents of change act quite rapidly such as a plow or a tractor, while others act quite slowly such as earthworms and roots. Recommended high priority research areas include to: improve and simplify measurements so that meaningful data can be collected; expand our infiltration data base to include the important temporal changes of the soil; and improve models to account for these temporal changes