Effect of tillage on rainfall infiltration and surface depressional storage
Mohamoud, Yusuf Mohamed
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https://hdl.handle.net/2142/19856
Description
Title
Effect of tillage on rainfall infiltration and surface depressional storage
Author(s)
Mohamoud, Yusuf Mohamed
Issue Date
1989
Doctoral Committee Chair(s)
Ewing, Loyd K.
Department of Study
Agricultural and Biological Engineering
Discipline
Agricultural Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Agricultural
Language
eng
Abstract
Research to evaluate the effects of tillage on rainfall infiltration and surface depressional storage was conducted. A method that generates infiltration, surface depressional storage, detention storage and hydraulic conductivity from data obtained from small field plots receiving simulated rainfall was developed. Values of Manning's resistance coefficient and overland flow velocity were calculated using the detention storage depth. Comparisons between observed and calculated overland flow velocities were made.
A laboratory experiment was conducted to quantify the amount of rainfall intercepted by residue at different rainfall intensities and durations. A maximum of 1.5 mm and 1 mm was intercepted by corn and soybeans, respectively. Laboratory experiments to determine tillage-induced soil hydraulic properties were conducted. Soil hydraulic properties were determined for three common surface conditions of a Catlin tilled soil; freshly tilled, protected (no-till), and crusted condition. These soil hydraulic properties were employed to simulate rainfall infiltration of tilled plots using Richards' equation.
The effects of tillage treatment and row direction on rainfall infiltration and surface depressional storage were determined by statistical analysis. The tillage treatments considered were conventional, no-till and disk/chisel, each with contour and up-and-down slope row direction. Among the tillage treatments studied, conventional tillage treatments had lower infiltration depths compared to conservation tillage treatments (chisel/disk and no-till). However, conventional plots with rows on the contour have greater depression storage depths compared to conservation tillage treatments with contour row directions.
A procedure to determine parameters of one-layered and two-layered Green and Ampt infiltration equation was developed and was used to predict rainfall infiltration of crusted and protected Catlin soil. Furthermore, a finite element formulation of the one-dimensional unsaturated water flow equation (Richard's equation) was used to predict rainfall infiltration for crusted and protected tilled field plots. Comparisons of rainfall infiltration depths of crusted plots simulated by Richards' equation and the Green and Ampt equation were made. Richards' equation predicted infiltration of a crusted soil very well while the Green-Ampt model predicted infiltration fairly well.
Using the Green and Ampt parameters, a low pressure center pivot irrigation system design procedure example was used to demonstrate the effect of tillage on infiltration and, thus, the operating pressure of the system. The analysis showed that no-till systems can be more suitable for smaller operating pressure compared to conventional tillage. However, quantification of economics and energy savings involved were beyond the scope of this research.
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