Analysis and modeling of flow systems in soils under different topographic and land use conditions

TERRECO WP 2-10

Von 03/2009 bis 01/2013

Projektleiter: Bernd Huwe, Stefan Peiffer, John Tenhunen
Mitarbeiter: Marianne Ruidisch, Camila Gaviria
Bewilligung: IRTG 1565 WP II TERRECO - Complex Terrain and Ecological Heterogeneity - Evaluating ecosystem services in production versus water yield and water quality in mountainous landscapes

 

Abstract 2011: The current status of the dryland farming agricultural practices under monsoonal conditions, namely plastic mulch ridge cultivation, and its impact on flow processes, soil erosion and nitrate transport was investigated in detail. A variety of field measurements and tracer experiments in combination with process-based numerical modeling techniques were used to identify the main characteristics of soil hydrological processes such as soil water dynamics, preferential flow, surface runoff, soil erosion and nitrate leaching. On hillslopes, we investigated surface and subsurface flow processes in four plastic mulched potato fields using a monitoring network of tensiometers and water content sensors as well as runoff collectors in combination with flow dividers (see Project WP2-07). Since these measurements do not consider preferential flow paths, we additionally carried out tracer experiments using the dye Brilliant Blue FCF. In the center of the catchment we investigated nitrate concentrations in flat radish cultivation (see Project WP2-05). The datasets we obtained of matric potentials, surface runoff, soil loss and nitrate concentrations were used to calibrate the HYDRUS 2/3D, EROSION 3D and HydroGeoSphere model in order to quantify drainage water fluxes, surface runoff, erosion and nitrate leaching rates of plastic mulched ridge tillage (RTpm) compared to ridge tillage without coverage (RT) and conventional flat tillage (CT). The simulations showed that plastic mulching substantially increases surface runoff up to 65 %, whereas drainage water decreases up to 16 %. On hillslopes, the dye tracer experiments showed that water is funneled preferentially above the tillage pan downhill. Unexpectedly, there was no macropore flow in deeper soil depth indicating a low risk of groundwater pollution by highly mobile solutes such as nitrate. Furthermore, the erosion study showed that plastic mulched ridge tillage increases soil erosion rates up to 42%. In terms of nitrate leaching, plastic mulching was found to have positive effects. We conclude that the current management of dryland fields on hillslopes can be enhanced in terms of reducing runoff and soil erosion during monsoon by best management practices such as the application of perforated plastic mulch as well as buffer zones between river and fields. In flat areas, where runoff processes are absent, plastic mulching, split applications and a better placement of fertilizer can help to decrease groundwater pollution risk.            

Summary

 

 

 

Typical dryland farming management in South Korea: Ridge cultivation with plastic mulch

 

Abstract 2013: The typical dryland farming agricultural practice under monsoon climate conditions in South Korea, namely ridge cultivation with the use of plastic film mulching, and its impact on flow processes, soil erosion and nitrate transport in seepage was investigated in detail. Tracer experiments and long-term field measurements were conducted together with process-based numerical modeling to identify and quantitatively describe soil hydrological processes, e.g., soil water dynamics, occurrence of preferential flow, surface runoff, soil erosion and nitrate leaching. On hillslopes, we investigated surface and subsurface flow processes in four plastic-mulched potato fields using a monitoring network of tensiometers and water content sensors, as well as runoff collectors that necessarily included flow dividers. Additionally, since these measurements did not consider preferential flow paths, we carried out tracer experiments by applying the dye Brilliant Blue FCF. On a level field in the center of the catchment, we investigated soil gradients in nitrate concentration over time with radish cultivation. The datasets we obtained on matric potentials, surface runoff, soil loss and nitrate concentrations were used to calibrate the HYDRUS 2/3D, EROSION 3D and HydroGeoSphere models. These were applied to quantify drainage water fluxes, surface runoff, erosion and nitrate leaching rates with plastic-mulched ridge tillage (RTpm) as compared to ridge tillage without coverage (RT) and conventional tillage without ridges (CT).

The simulations demonstrated that plastic mulching substantially increases surface runoff by as much as 65 %, whereas drainage is decreased up to 16 %. On hillslopes, the dye tracer experiments showed that water is moved downhill preferentially above the tillage pan. Unexpectedly, there was no macropore flow in deep soil layers, suggesting a low direct risk of groundwater pollution by this means with highly mobile solutes such as nitrate. The erosion studies showed that plastic mulched ridge tillage increases soil erosion rates up to 42%. In terms of nitrate leaching, plastic mulching was found to have positive effects. We conclude that reductions in runoff and soil erosion during the monsoon can be achieved in dryland fields on hillslopes by implementation of improved management, such as the application of perforated plastic mulch or increasing the width of buffer zones between river and fields. In flat areas, where runoff processes are absent, plastic mulching along with techniques that would allow multiple fertilizer applications and a better placement of fertilizer into ridges would help to decrease groundwater pollution risks.

The information will be used during cohort 2 studies in a postdoctoral project with SWAT model to link nitrogen exports from agricultural fields with observations of N transport in the stream system of Haean Catchment. The objective is to improve SWAT as an effective tool for estimating N transport to the Soyang Lake Reservoir with variable climate and land use.

Key words: soil water dynamics, preferential flow, surface runoff, soil erosion, nitrate leaching, best management practices  

 

Poster Workshop Ecosystem Change and Society, Bayreuth, January 2013

 

 

 

 

 

 

 

 



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