Date of this Version
Volkmer, A.J. 2014. Infiltration and runoff parameters for tilled and no-till row crops. M.S. thesis. Lincoln, NE. University of Nebraska, Biological Systems Engineering Department.
Infiltration and runoff are hydrologic processes that effect the amount of water available to plants, for groundwater recharge, and for stream flow. No-till planting (NT) is a management practice used to reduce soil erosion, increase water infiltration, and reduce soil water evaporation, and can have great impact on infiltration and runoff. An investigation was conducted to determine the impact of NT on infiltration and runoff when compared to tilled conditions.
Runoff and precipitation data was gathered from sites at Fillmore County, NE, Phelps County, NE, the USDA-ARS North Appalachian Experimental Watersheds (NAEW) near Coshocton, OH, and the Lennoxville Research Station (LRS) in Quebec, Canada. Each site consists of at least one NT treatment, and one tilled treatment.
Average curve numbers (CN) from the NRCS CN method were determined for each site. A relationship between annual series and partial duration series (PDS) was developed, and used with a standard NRCS method to determine average CN. NT CN was an average of 5 points lower than the tilled sites, indicating NT sites had less runoff than the tilled sites. It was also determined that experimental CN’s were an average of 6.2 points lower than tilled CN’s published in the NRCS National Engineering Handbook.
A method was also developed that uses reference hydraulic conductivity (Kref) values in conjunction with land-use coefficient (CL) values to determine effective hydraulic conductivity values for different tillage types. The resultant effective hydraulic conductivity (Ke) value is used in the Green-Ampt equation to model infiltration and runoff depths. Six different methods used to determine Kref were evaluated. It was determined that using ROSETTA, WEPP, and Hydrologic Soil Group criteria for Kref with CL values resulted in the most accurate prediction of runoff depths at the Phelps County, Fillmore County, and NAEW sites. Values for CL were 3-4 times higher for NT than for tilled conditions.
A comparison was made between using adjusted CN’s for tilled and NT conditions, and the CL method with the Green-Ampt equation. The CN method predicted runoff depths more accurately at Phelps County, Fillmore County, and NAEW. Using ROSETTA and HSG to determine Kref with the CL method produced the most accurate runoff predictions at the two watersheds in Lancaster County, NE.
Advisor: Dean E. Eisenhauer