Submitted to: Hydrological Processes
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2005
Publication Date: 3/31/2007
Citation: Kozak, J.A., Ahuja, L.R., Green, T.R., Ma, L. 2007. Modelling Crop Canopy and Residue Rainfall Interception Effects on Soil Hydrological Components for Semi-Arid Agriculture. Hydrological Processes. 21:229-241. Can be accessed at doi: 10.1002/hyp.6235. Interpretive Summary: Crop leaves and residues have been shown to collect and trap (intercept) a significant amount of rainfall. However, interception often has been overlooked in hydrologic modeling efforts. A model was developed to account for these processes and incorporated in the ARS Root Zone Water Quality Model (RZWQM). This generalized model was validated and compared to three hypothetical studies and one field experiment. Interception was observed to decrease the amount of water entering the soil and the amount of water evaporating and being taken up by plants.
Technical Abstract: Crop canopies and residues have been shown to intercept a significant amount of rainfall (as much as 50-60% of a small rainfall event). However, rainfall or sprinkler irrigation interception often has been overlooked in hydrologic modeling efforts. Crop canopy interception is controlled by canopy density and rainfall intensity and duration. Crop residue interception is a function of crop residue type, residue density and cover, and rainfall intensity and duration. We account for these controlling factors and present a model for both interception components based on Merriam's approach. The developed model was applied and validated using results from two field studies and one laboratory study before being input into the ARS Root Zone Water Quality Model (RZWQM). Using this enhanced version of RZWQM, three studies were performed to examine the quantitative effects of rainfall interception by corn and wheat canopy and residue on the components of the soil-water mass balance in a semi-arid environment. Study I consisted of ten separate growing seasons (1991-2000) for canopy effects and ten non-growing seasons (1991-2000) for residue effects in eastern Colorado conditions. For actual management practices in a no-till wheat-corn-fallow cropping sequence at Akron, Colorado, a ten-year RZWQM simulation was performed to examine the overall effects on water balance and crop growth caused by rainfall interception by both crop canopy and residue (Study II). Finally, to examine a higher precipitation environment, a no-till wheat-corn-fallow rotation scenario at Corvallis, Oregon was simulated (Study III). For all studies, interception was shown to decrease infiltration, runoff, ET, deep seepage, macropore flow, soil water storage, leaf area index, and crop/grain yield. Because interception decreased both infiltration and ET, no significant change in soil water storage was observed. The effects of interception on both environments were small. Nonetheless, this is a useful finding for other hydrologists to know.